US 2023/0305289 Al

up. The triangular open symbols are concentrations that
precipitate at room temperature. The shaded area illustrates
compositions that lead to the formation of SeedGel embodi-
ment. The solid line indicates the ‘optimal’ conditions for
obtaining bicontinuous structures with well-defined repeat
ing distance.

[0061] FIG. 6A: Schematic drawing illustrating the
experimental setup in scattering mode.

[0062] FIG. 6B: Schematic drawing illustrating the experi-
mental setup in transmission mode.

[0063] FIG. 6C: Photographs of SeedGel embodiment
with tunable structural color recorded in scattering mode at
different temperatures. White light source is used.

[0064] FIG. 6D: Photographs of SeedGel embodiment
with temperature-dependent wavelength filtering in trans-
mission mode during cooling. The colored word “SeedGel
embodiment” displayed by an OLED screen

[0065] FIG. 7: Normalized transmission spectra of Seed-
Gel embodiment as a function of wavelength at varied
temperatures. By increasing the temperature, the transmis-
sion peak shifts towards longer wavelength.

[0066] FIG. 8: The effect of path length on the peak width
of the transmitted light of SeedGel embodiment with both
calculation and experimental data are shown.

[0067] FIG. 9: Transmission spectra of SeedGel embodi-
ment as a function of wavelength that covers UV-visible to
near infrared range at different temperatures.

[0068] FIG. 10A: Transmittance spectra of SeedGel
embodiment samples prepared with binary solvents of
water/2,4-lutidine at different temperatures.

[0069] FIG. 10B: Transmittance spectra of SeedGel
embodiment samples prepared with binary solvents of
water/3-methylpyridine at different temperatures.

[0070] FIG. 11: Transmission spectra of SeedGel embodi-
ment samples prepared with binary solvents of water/2,6-
lutidine shows sensitive response of the peak to the tem-
perature change.

[0071] FIG. 12: UV-vis transmittance spectra of a SeedGel
embodiment prepared with binary solvents of water/deuter-
ated 3-methylpyridine at a temperature range of 24-90° C,
[0072] FIG. 13: UV-vis transmittance spectra of a SeedGel
embodiment prepared with binary solvents of water/2-meth-
ylpyridine at a temperature range between 75-98° C.
[0073] FIG. 14: UV-vis transmittance spectra of a
microparticle dispersion in a binary solvent of toluene and
n-hexane. The ratio indicates the volume fraction of toluene
in the binary solvent mixture of toluene and n-hexane.

DETAILED DESCRIPTION OF THE
INVENTION

[0074] As used herein, the term “SeedGel embodiment”
refers to the solvent segregation driven gel state of the
composition of the present invention.

[0075] As used herein, the term “water/lutidine” binary
solvent system refers to binary solvent systems comprising
water and/or partially deuterated water as one solvent and
second solvent to include at least one of Iutidine and/or its
isomers; or deuterated or partially deuterated lutidine and its
isomers. For example, as used herein, the binary solvent
system of “water/lutidine” may include, but is not limited to,
water/2,6-lutidine; water/2,5-lutidine; _ water/2,4-lutidine;
water/2,3-lutidine; water/3,4-lutidine; _ water/3,5-lutidine;
partially deuterated water/2,6-lutidine; partially deuterated
water/2,5-lutidine; partially deuterated water/2,4-lutidine;

Sep. 28, 2023

partially deuterated water/2,3-lutidine; partially deuterated
water/3,4-lutidine; partially deuterated water/3,5-lutidine;
water/deuterated 2,6-lutidine; water/deuterated 2,5-lutidine;
water/deuterated 2,4-lutidine; water/deuterated 2,3-lutidine;
water/deuterated2,4-lutidine; water/3.5-lutidine; water/par-
tially deuterated 2,6-lutidine; water/partially deuterated 2,5-
lutidine; or water/partially deuterated 2,4-lutidine; deuter-
ated water/2,3-lutidine; deuterated water/3,4-lutidine; or
deuterated water/3,5-lutidine.
[0076] As used herein, the term “alcohol/alkane” binary
solvent system refers to binary solvent systems comprising
an alcohol, a deuterated alcohol, a partially deuterated
alcohol or an isomer thereof as one solvent and second
solvent to include an alkane, a deuterated alkane, a partially
deuterated alkane, or an isomer thereof. Suitable examples
of alkane include C1-C3 alcohols, such as, methanol, etha-
nol, and propanol and isomers thereof. Suitable examples of
alcohol include C5-C12 alkanes and their isomers, but are
not limited to pentane, hexane, heptane, octane, nonane,
decane, undecane, dodecane and isomers thereof. For
example, the binary solvent system of “alcohol/alkane” may
include, but is not limited to, a C1-C3 alcohol/a C5-C12
alkane; a deuterated C1-C3 alcohol/a C5-C12 alkane; a
C1-C3 alcohol/a deuterated C5-C12 alkane; a deuterated
C1-C3 alcohol/a deuterated C5-C12 alkane; a partially deu-
terated C1-C3 alcohol/a C5-C12 alkane; a C1-C3 alcohol/a
partially deuterated C5-C12 alkane: a partially deuterated
C1-C3 alcohol/a partially deuterated C5-C12 alkane; a deu-
terated C1-C3 alcohol/a partially deuterated C5-C12 alkane;
ora partially deuterated C1-C3 alcohol/a deuterated C5-C12
alkane. In an embodiment, the binary solvent system may
comprise:

[0077] G) methanol, deuterated methanol, or a partially

deuterated methanol, and
[0078] Gi) hexane, deuterated hexane, or a partially
deuterated hexane.

[0079] In another embodiment, the binary solvent system
may comprise:
[0080] (i) ethanol, deuterated ethanol, a partially deu-

terated ethanol, and
[0081] (ii) dodecane, deuterated dodecane, or a partially
deuterated dodecane.
[0082] The present invention discloses bicontinuous
porous structures through colloidal assembly realized by
non-equilibrium process is crucial to various applications,
including water treatment, catalysis and energy storage.
Disclosed herein is a novel composition for SeedGel
embodiment formation, demonstrated to arrest bicontinuous
structures with excellent thermal structural reversibility and
reproducibility, tunable domain size, adjustable gel transi-
tion temperature, and amazing optical properties. It is
achieved by trapping nanoparticles into one of the two
solvent domains upon phase separation of the binary sol-
vent. Due to the universality of the solvent driven particle
phase separation, SeedGel embodiment is thus potentially a
generic method for a wide range of colloidal systems.

EXPERIMENT NO. 1: TUNABLE.
THERMO-REVERSIBLE BICONTINUOUS
NANOPARTICLE GEL DRIVEN BY THE
BINARY SOLVENT SEGREGATION,

Thermo-Reversible SeedGel Embodiment using
Spherical Silica Particles having 27 nm Diameter

[0083] FIG. 1B shows a schematic illustration of an exem-
plary composition comprising an effective amount of nan-


US 2023/0305289 Al Sep. 28, 2023
22

prising tuning the pore size by controlling the size of the two
micro domains by adjusting the temperature ramping rate.
15. The method of claim 14, comprising operating the
filter to selectively filter or block a component of a fluid.
16. The method of claim 15, wherein the fluid comprises
a solid/liquid system, solid/gas system, or a liquid/liquid
system.
17. A method of tuning radiation transmission compris-
ing:
(i) providing a composition comprising microparticles
dispersed in a binary solvent system, wherein a refrac-
tive index of the binary solvent is close to that of the
plurality of microparticles, and
(ii) tuning the transmission of radiation through the com-
position by changing a solvent fraction of the two
solvents of the binary solvent system,
wherein the microparticles and the binary solvent sys-
tem have different dependence of their respective
refractive index on wavelength, and

wherein the refractive index of the microparticles
matches with that of the binary solvent system at
certain compositions of the binary solvent system.

18. The method of claim 17, wherein the binary solvent
system comprises toluene and n-hexane.

19. The method of claim 17, wherein the binary solvent
system comprises a first solvent present in an amount of 45
to 65% by weight, based on the total weight of the binary
solvent system.

20. The method of claim 17, wherein the microparticles
have an average particle diameter in the range of from 1 ym
to 12 pm


US 2023/0305289 Al

Sep. 28, 2023 Sheet 13 of 14

Patent Application Publication

eT Old
(Wu) UjbuajaaepA
0001 008 009

T i

: ji saSibchoeperorineBnn ti eit BBOOON CNA Ai

sa EAE ELAR OA
neonate es,

02

OV

09

08

OOL

(%) SOUR IWSUEL


US 2023/0305289 Al

lation length (€) and periodicity (d). Their relationship is
illustrated in Supplementary Equation 1 through Supple
mentary Equation 4.

8ny,(1 ~ aX Apy

at
[ . eT 2
(4) +267 3
ase 4

where Ap is the difference of scattering length density (SLD)
and @, is the volume fraction of one domain, which can be
the volume fraction of either the particle domain or the
solvent domain. The fitting was performed by fixing other
parameters except the periodicity (d), correlation length (6).
and scale. The reason to let scale vary is to account for the
dynamic contrast change at varied temperatures between
particle and solvent domains, which originates from the
change of lutidine concentration in both water-rich and
lutidine-rich solvent regions. The periodicity distance
inchides both the average size of the particle domain and
solvent domain. If the ratio of the average domain size
between the solvent and particle domain is approximately
the volume ratio of these two domains, the average size of
the particle domain is estimated to be about 2 um, and the
size of the solvent channel is about 1.3 jm at 30°C. At 26°
C,, the particle domain increases to 7.1 ym and the solvent
channel to 4.5 um.

SUPPLEMENTARY TABLE 1-1

The resulted periodicity and correlation length from Teubner-
Suey model fitting of USANS data at different temperatures.

Temperature Periodicity Correlation Length
eC) (umm) (um)
30 3.34 1.80
29 3.38 173
28 3.37 175
27 3.52 1.80
26 11.6 3.66

Supplementary Note 1-2: Estimation of the Particle

Volume Fraction in the Particle Domain with Small

Angle Neutron Scattering (SANS) Fitting using the
Hayter-Penfold Method

[0114] In order to estimate the volume fraction of particles
in the particle domain, SANS data at relatively high-q was
fitted using the Hayter-Penfold model. Because the domain
size is much larger than the particle diameter, most particles
in the particle domain are not at the interface. As no
additional salt is added into the solution and particles are
highly charged, a strong long-range screened charge repul-
sion exists between particles. Therefore, in order to calculate
the interparticle structure factor with a long-range repul-
sion, the Hayter-Penfold model was used. Additionally, an
attempt was made to fit the SANS pattern at high-q with
other interaction models, such as pure hard sphere interac
tion, and the interaction with a short-range attraction and

Sep. 28, 2023

long-range repulsion. The charge interaction model was
found to give the best fitting results.

[0115] To fit the SANS scattering results of concentrated
particle solutions, an independent experiment was per-
formed to obtain the information of the form factor: the
radius of the sphere and the size polydispersity by fitting a
scattering curve of a dilute particle dispersion in water
(volume fraction of 0.5%).

[0116] In this model, the scale factor, volume fraction of
spheres, as well as the charge on the sphere surface were
used as fitting parameters. All the rest of the parameters were
fixed at constant values. The scale factor was determined to
be 0.697 and the local volume fraction to be 0.391.

Supplementary Note 1-3: Estimation of the Relative
Concentration of Lutidine and Water in the Particle
Domain

[0117] The 2,6-lutidine ratio in the particle domain was
estimated based on the results from contrast matching
experiment shown in FIGS. 3A and 3B above. It should be
noted that the intensity of the structure factor peak reduces
by more than five times when changing from the liquid state
to the gel state for this sample. This is due to the enrichment
of water concentration in the particle domain. By using the
SANS intensities of the inter-particle structure factor peak at
different temperatures, the concentration of lutidine can be
calculated with the Supplementary Equation 5 through
Supplementary Equation 15.

MA, 20° C)~Ieug _ Bp(A, 20° CIPPRO?_C)S(2O”_C.) 5
HA, 30° C.)= ling (ApCA, 30° CP PBO? C.)SBO? C.)
1B, 20° C.)~ long _ QpB, 20? C.F? PAW’ CISA” C.) 6
TB, 30° C)= Ing ~ (QptB, 30° CP PRO” CISBH C)
) 1
Ing) _ pla, 20° C7 APB, 30° 6)?
) (AplA, 30° C.)7(AptB 20°C)?
Apt, 20° C.) 8
SLDttioa — (P 4,Lusidine»SED taaiaine + Pmaschedwater,SLDypatchadvater)
AplA, 30° C)= 9

SLD stca ~ (Psitind SED tarsi Pmtchetvoer SED matchdvter)
APB, 20° C.) = SLD etica — (¥B,.uidined SLD bwridine + PH1y0,SLD 1,0) 10

APB, 30° C.) = SLD sia — (a,tuidined SED tine + PH04SLDyo) = V

Pastusdines = 1 — Pmatchotvaers R
PAdLuidined =~ Pmachedwaerd 13
Pa,tundines = 1 PryO8 14
Pa.tundned = 1 Pr00 15

where A and B denote samples with and without SLD of
water matched to that of silica, as described in the main text.
1(20° C.) and 1(30° C.) are the peak intensity of SANS
pattern at 20° C. and 30° C. Lye, and I,.,-are the intensity of
the incoherent background for sample A and B, respectively.
Pis the intensity of the form factor at the peak position, and
Sis the value of the inter-particle structure factor at the peak


Patent Application Publication Sep. 28, 2023 Sheet 4 of 14 US 2023/0305289 Al

12 a Contrast Matched
1st 2nd
107 ° A =< 20°C
oe) oO 30°C
8
S 6 :
At & 4
ag ps
J
2r es,
a ry rr aa 2 4
0.001 0.01 4 0.1 FIG. 3C
a(A’)
FIG. 3A
60 No Contrast Match
50- 1st 2nd
° A => 20°C
40- & [e) O 30°C
os
= 30} &
= g :
20+ 4
10+
Ona STS 2 4
0.001 0.01 1 0.1 FIG. 3D
a(A’)

FIG. 3B


US 2023/0305289 Al

20

[0186] It is important to note that pure 2,6-lutidine is a
colorless liquid and an oxidized/degraded 2,6-lutidine may
turn slightly yellow that can shift the transition temperature
and phase diagram.

[0187] Consequently, homogenous solutions were
obtained that showed structural color and tunable optical
transmission in its gel state at elevated temperatures.
[0188] Following the convention currently adopted in the
field, unless otherwise noted, volume fraction over the total
sample volume is used to describe the concentration of silica
particles, and the relative 2,6-lutidine concentration in the
binary solvent system is expressed as mass fraction.
[0189] The table below summarizes various compositions
for SeedGel embodiments that were used hereinabove to
achieve dynamically tunable light transmission.

Sep. 28, 2023

scattering data to absolute intensity. The USANS experi-
ments were conducted on BT-5 to cover a g-range between
3x10-° ATM! and 0.001 A!. The temperature was controlled
by circulation thermal bath. All the data reduction was
performed using standard Igor (Wavemetrics, Portland, OR)
macros. The fitting of the results was conducted using the
SAS View software.*°

[0191] For the contrast matching experiment using SANS,
D,O was mixed with Ludox® TM/SM solution so that the
volume ratio of D,O to HO in the dispersion was 58:42
The scattering length density (SLD) of water phase was thus
matched to that of silica. The addition of D,O only slightly
changed the solution PH value (by about 0.3), which did not
alter the stability of silica nanoparticles. An Amicon cen-
trifugal filter unit (Ultra-15, MilliporeSigma, Burlington,

Mass fraction of

Silica Solvent Ain the Particle
particle binary solvent volume elation Correlation
Solvent A Solvent B Size system fraction ‘Temperature Periodicity Length
2,6-lutidine 27 nm 243% 26°C.
2,6-lutidine) Os: 27 nm 24.3%
mixture
2.4-lutidine 1,0 27 um Inc.
2,5-lutidine 1,0 27 nm re
2,6-lutidine 1,0 10 nm
1,0 27 nm
1,0 27 nm 12.6 um 2.58 jm
1,0 27 om 2.68 jum 0.55 yum
1,0 27 nm
1,0 27 nm
2,6-lutidine 1,0 27 om 2.65 jum 0.52 um
2,6-lutidine 1,0 27 nm
2,6-lutidine 10 27 um
2,6-lutidine 1,0 37 um
2,6-lutidine 1,0 27 nm
2,6-lutidine 1,0 27 om 2.68 um 0.49 um
1,0 27 nm 297mm 0.53 jum
. 1,0 27 nm
2methylpyridine —_HjO 27 om ne
3-methylpyridine —-HZO 27 nm 22.7% 41°C.
d-3-methylpyridine HO 27 nm 2% SPC.
‘Toluene n-Hexane 1-12 ym 2.2%

43%, 41%, & 39%

METHODS

Small Angle Neutron Scattering (SANS) and
Ultra-Small Angle Neutron Scattering (USANS)

[0190] Both SANS and USANS experiments were con-
ducted at NIST center for neutron research (NCNR, Gaith-
ersburg, MD). Both NG7 and NGB30 were used to collect
SANS results. Scattering patterns from three detector posi-
tions, including lens, were recorded to provide a q-range of
0.001 A-'<q<0.45 A-'. Peltier-Driven heating/cooling
blocks were utilized to control temperatures with a precision
of +0.1° C. At least 30 min waiting time was implemented
before measuring the scattering data after each temperature
change to ensure that the equilibration was achieved. The
sample was sealed by a demountable titanium cell with a
path length of 1 mm with a Teflon coated O-ring. The
scattering from a pair of quartz windows were properly
subtracted. The open beam flux and transmission of each
sample at every detector position was recorded to bring the

MA) equipped with a membrane of 3 kDa pore size was used
to filtrate out excess water. Centrifugation (Centrifuge 5702,
Eppendorf, Hauppauge, NY) with relative centrifugal force
(rcf) of 3000xg for around 30 min was used to concentrate
nanoparticles close to their original volume fraction. Then
desired volume of 2,6-lutidine was added to contrast
matched silica dispersion for SeedGel embodiment forma-
tion with 27 nm and 10 nm particles.

Laser Scanning Confocal Microscopy (LSCM)

[0192] A confocal microscope (Zeiss model LSM 800,
Thornwood, NY) with a 561 nm laser and 50x/0.5 air lens
was used to conduct the LSCM experiment. A scanning
z-step of 0.5 jum and an aperture size of 119 um was used
The image acquisition was performed in fluorescence mode,
using a fluorescent dye (Rhodamine B) that has a favorable
aflinity to the 2,6-lutidine rich phase. A quartz sample cell
containing SeedGel embodiment was fit tightly into a cus-
tomized sample holder, which was designed to allow a



US 2023/0305289 Al

oparticles 110 dispersed homogeneously in a binary-solvent
system 120 comprising a first solvent and a second solvent.
At a temperature below a first temperature T,, the binary
solvent system 120 is in a single-phase and in a liquid state.
The nanoparticles 110 and the binary solvent system 120 are
chosen, such that the nanoparticles 110 have a preferential
wettability to the first solvent.

[0084] As shown in FIG. 1B, when the composition 100 is
heated above the first temperature T,, the composition
transitions thermo-reversibly from the liquid state 100 to a
gel state 101. The gel state 101 comprises bi-continuous
domains including a particle domain 130 and a solvent
domain 135. As schematically illustrated in FIG. 1B, the
particle domain 130 comprises nanoparticles 110 dispersed
in a first-solvent-rich fraction 121 of the binary solvent
system 120 and the solvent domain 135 comprises a second-
solvent-rich fraction 122 of the binary solvent system 120.
[0085] Thus, in order to prepare a SeedGel embodiment of
the composition, nanoparticles need to be dispersed in a
binary solvent system in its single-phase region. By chang-
ing the temperature, by heating or cooling, towards the
critical temperature of the binary solvent system, a SeedGel
embodiment can be formed by jamming nanoparticles in one
of the solvent regions. There are two prerequisites for a
composition to form a SeedGel embodiment: 1) a binary
solvent system that nanoparticles can be dispersed in is at the
single-phase region in the liquid state of the binary solvent
system, i.e. there is no strong intrinsic attraction between
nanoparticles and the nanoparticles are stable in the single-
phase region of this binary solvent system; 2) the surface of
nanoparticles need to be tuned to strongly favor one com-
ponent of the binary solvent system.

[0086] The thermodynamic origin of the bicontinuous
structure formation in SeedGel embodiment is believed to be
kinetically arrested spinodal decomposition. Once the par-
ticle domain forms, particles prefer to stay in the water-rich
domain as water preferentially adsorbs on their surfaces.
Within the particle domain, the particles transition into a
glassy state that provides the mechanical strength of Seed-
Gel embodiment.

[0087] Any suitable nanoparticles may be used, including,
but not limited to silica nanoparticles, polystyrene particles,
poly(methyl methacrylate) (PMMA) particles, iron oxide
nanoparticles, calcium carbonate nanoparticles, and carbon
nanoparticles. The nanoparticles can have any suitable aver-
age particle diameter, such as in the range of from 5 nm to
100 nm or from 7 nm to 75 nm, or from 8 nm to 50 nm.
Additionally, any suitable method can be chosen to make the
nanoparticles have affinity to the first solvent, including, but
not limited to chemical or physical surface modification of
the nanoparticles. For example, in an embodiment of the
composition comprising the binary solvent system of water!
2,6-lutidine, silica nanoparticles having high surface charge
can be used, where the silica nanoparticles have a prefer-
ential wettability to water.

[0088] Suitable examples of binary solvent system
include, but are not limited to,

[0089] (i) water, deuterated water, or partially deuter-
ated water and methylpyridine, dimethyl pyridine, deu-
terated or partially deuterated methylpyridine, deuter-
ated or partially deuterated dimethylpyridine, or
isomers thereof;

[0090] (ii) water and methyl ethyl ketone;

[0091] (iii) an alcohol and an alkane;

Sep. 28, 2023

[0092] (iv) ethylene carbonate and p-xylene;
[0093] _(v) ethylene glycol and nitromethane; or
[0094] (vi) cyclohexane and nitromethane,

[0095] Inan embodiment, the composition comprising any

of the above binary solvent systems (i)-(ii) upon heating
above the first temperature T1, thermo-reversibly transitions
from the liquid state to a gel state. In an embodiment, the
composition comprising any of the above binary solvent
systems (i)-(ii) upon cooling below the first temperature T1,
thermo-reversibly transitions from the liquid state to a gel
state. In another embodiment, the composition comprising
any of the above binary solvent systems (iii)-(vi) upon
cooling below the first temperature T1, thermo-reversibly
transitions from the liquid state to a gel state.

[0096] Although examples (ii) and (iii) list specific binary
solvent systems comprising an alkane and an alcohol, suit-
able systems may comprise any suitable alkane and any
suitable alcohol for the purpose desired, such as but not
limited to binary solvent systems with an alcohol including
but not limited to methanol, ethanol, propanol, and isomers
thereof and with an alkane including but not limited to
C5-C12 alkanes, such as pentane, hexane, heptane, octane,
nonane, decane, undecane, dodecane, isomers thereof. The
binary solvent system may comprise a deuterated or a
partially deuterated derivative of any of these alcohols and
alkanes.

[0097] In another embodiment of the composition, the
nanoparticles may be dispersed in an amount of 5% to 50%,
or 7.5% to 45%, or 9% to 30%, by volume in the binary
solvent system, based on the total volume of the composi-
tion. The composition may include binary solvent system
comprising the solvent having no affinity to the nanopar-
ticles in the range of 15% to 50%, or 16% to 45%, or 20%
to 42% by mass based on the total mass of the binary solvent
system. However, it should be noted that the amount of the
nanoparticles and the binary solvent composition present in
the composition for the SeedGel embodiment are interde-
pendent and cannot be randomly selected for SeedGel
formation.

[0098] In an aspect, an exemplary composition of the
SeedGel embodiment comprises spherical silica nanopar-
ticles (average diameter of approximately 27 nm) dispersed
ina binary solvent system comprising a mixture of water and
2,6-lutidine. The nanoparticles have high surface charge
such that its surface is preferentially wetted by water. As a
result, the nanoparticles have a net repulsion between them.
The solvent ratio in the binary solvent system is adjusted
close to critical concentration of the bulk solvent (mass
fraction of 28.4% 2,6-lutidine and 71.6% water in the
solvent) with the particle volume fraction at 24.3%. This
sample is in the liquid state at room temperature (20° C.) and
forms a gel (SeedGel embodiment) at higher temperatures.
[0099] In an embodiment, silica nanoparticles having an
average diameter of 10 nm have a zeta potential in the range
of -22 mV to 45 mV or -30 mV to -35 mV. In another
embodiment, silica nanoparticles having an average diam-
eter of 27 nm have a zeta potential in the range of -10 mV
to 70 mV or -37 mV to -41 mV.

[0100] FIG. 3A shows a 3-D confocal microscope image
of the above exemplary composition in the gel state, at a
temperature close to 29° C., which shows a tortuous bicon-
tinuous structure with a domain size on the order of a few
micrometers. Quantitative temperature-dependent character-
izations of the multi-length scale structures were conducted


US 2023/0305289 Al
12

gel at elevated temperatures. This is most likely because not
enough aggregates are formed to percolate throughout the
sample upon heating as a result of low particle and 2,6-
lutidine concentrations.

Controlling Domain Size by Temperature Ramping
Rate

[0130] In an embodiment of the composition, the size of
each of the particle micro-domain and the solvent micro-
domain is dependent upon a temperature ramping rate of the
thermo-reversible transition of the composition from the
liquid state to the gel state. In an embodiment, the tempera-
ture ramping comprises heating the composition from a
lower initial temperature (liquid state) to a higher tempera-
ture (gel state). In another embodiment, the temperature
ramping comprises cooling the composition from a higher
temperature (liquid state) to a lower temperature (gel state).
In particular, the domain size of a SeedGel embodiment of
the composition disclosed herein can be manipulated by
controlling the temperature ramping rate. USANS profiles of
the above SeedGel embodiment (the particle volume firac-
tion over the total sample volume was about 24% and the
2,6-lutidine mass fraction in the binary solvent system was
28.4%) at four different ramping rates(0.1, 0.5, 1, and 2°
C./min) were compared and domain sizes were determined
by fitting USANS data with the Teubner-Strey model, sum-
marized below. The domain size was found to be dynami-
cally adjusted. It was found that faster ramping rate leads to
a smaller domain size, whereas a slower quenching results
in a larger domain size.

‘Temperature Ramping Rate

041° Cymin 05° C/min 1° Cin 2° Cin
Particle domain 72 2.45 2.02 1.61
size (um)

Solvent domain 2.34 1.55 1.27 1.01
size (um)

[0131] _In particular, Experiments were designed to heat a

sample from 20° C. (liquid state) to a final temperature of
30° C. (gel state) to form a SeedGel embodiment with four
different temperature ramping rates. It was found that the
peak position shifted from approximately 8x10TM° Av! to
2x107* A~" by changing the ramping rate from 0.1° C./min
to 2° C./min. The ramping rate used here is the actual
quenching speed that was measured within the sample. A
careful calibration was performed by correlating the control
temperature ramping rate to the actual temperature change
speed using a temperature sensor placed inside a SANS cell
The measured temperature inside the SANS cell was plotted
as a function of time and a straight line was observed for
slow ramping rates: 0.1° C./min and 0.5° C./min. As dis-
cussed in Example 1, the gelation temperature fora SeedGel
embodiment sample with an identical concentration is at
about 26° C. The temperature ramping rate matters the most
around the gelation temperature to determine the domain
structure. This is suggested from the fact that no structural
change was observed at temperatures higher than 26° C.
Also, the domain structure right at 26° C. deviated from
those formed at temperatures above the gelation point. Thus,
the ramping rate crossing 26° C. is considered as the actual
rate that determines the gel structure of a SeedGel embodi-

Sep. 28, 2023

ment. For the slow settings (0.1° C./min, 0.5° C./min, and 1°
C/min), the measured curves were linear in this region and
the calibrated ramping rates of the sample were close to the
ramping rate of the control temperature. At higher ramping
rates for the control temperatures, the temperature increase
started to slow down when getting close to the set tempera-
ture. Due to the control loop mechanism employed by
typical PID controllers, the closer to the setpoint, the more
reduction of the ramping rate. This was found to be espe-
cially true in the fastest ramping rate of 10° C./min. To
accurately determine the heating speed for the set value of
10° C./min, the range between 24° C. and 26° C. was used
for linear fitting. Table S2-3 in the Supporting Information
summarizes the calibrated ramping rates corresponding to
each set value. The obtained periodicity by Teubner-Strey
model fitting (was plotted as a function of calibrated ramp-
ing rate (r). It was found that the fast ramping rates could
effectively reduce the domain size. Ramping rates were
shown to have a clear linear dependence of the periodicity
on the ramping rate in a semi-log scale. Furthermore, the
experimental data was fitted to obtain an empirical relation-
ship between domain size and the ramping rate. This empiri-
cal relationship can be useful for designing the desired
domain size by controlling the temperature ramping rate.
The periodicity dependence on the ramping rate is attributed
to the kinetical competition between percolation and nucle-
ation growth. At fast ramping rates, small aggregates are
formed from local phase separation near particles and used
to form percolation with narrower channels.

[0132] It is important to point out that the change of the
ramping rate does not affect the distribution of the period-
icity of domain structures determined before. Hence, the
optimal sample composition identified in the schematic
phase diagram shown in FIG. 5 is not expected to be affected
by the ramping rate. However, the exact domain size for
these samples may be further affected by the ramping rate.
[0133] Thus, for a SeedGel embodiment, controlling the
ramping rate is a simple and effective way to change the size
of the bicontinuous channels due to its thermo-reversibility
and stability.

Quasi-Static Heating

[0134] The structure of the exemplary composition for the
SeedGel embodiment was tested by increasing the tempera-
ture from liquid to its gel state. SANS profiles were recorded
at each temperature upon heating. Considering the time for
the measurement, ramping and equilibration, it took about
an hour at every temperature point. It was found that gels can
be successfully formed even with a very slow ramping rate
(0.1° C/min) as discussed hereinabove. This is in sharp
contrast to the fast quenching rate required in many Bijel
systems. The quasi-static temperature change relaxes the
restriction in sample size and makes the gel formation easily
scalable to a large sample volume. At the same time, the
ability to generate SeedGel embodiment even at very slow
ramping rate provides an additional knob to control the
domain size.

[0135] Similar to FIG. 2B, the charge repulsion dominates
the interactions between silica particles at 20° C. A well-
defined peak at high-q (approximately 0.023 A~') is due to
the correlation between nearest neighbor particles with a
strong charge repulsion. Right below gelation transition
temperature (24° C.), a broad peak at q-values between
0.001 A“ and 0.01 A“ is observed. This indicates that the


US 2023/0305289 Al

reproducible when following the same heating protocol. In
addition, the gel structure is very stable after at least 20 h of
aging at 30° C. and no change of domain structures was
observed by USANS within a reasonable duration of period.
(Details are in Supplementary Note 1-5)

‘Thermo-Reversibility

[0108] FIGS. 4A and 4B demonstrate feasibility, thermal
reversibility, and structural reproducibility of SeedGel
embodiment using spherical silica particles with 10 nm
diameter by performing similar experiments shown in FIGS.
2A and 3B. Note that the 2” curve in FIG. 4A shows slightly
higher intensity of low-q scattering when compared to that
of the 1° curve in the liquid state at 20° C. This change is
due to the fact that a small amount of random sized aggre-
gates that are not fully dissolved in the sample after the
previous formation of SeedGel embodiment due to its slow
kinetics. The fast advancement in nanoscience has success-
fully produced many interesting colloidal particles with size
down to sub-10 nm in the past decades. One of the most
successful examples is quantum dot with unique electrical
and optical properties. SeedGel embodiment works very
well with small size particles, opening up a window for
many interesting colloidal particles with size down to 10 nm.
that are rather difficult to form Bijels.

Controlling Gelation Temperature by Tuning Binary
Solvent System

[0109] The composition for the SeedGel embodiment has
a broad range of adjustable gelation temperature as the
gelation temperature can be tuned by controlling the prop-
erty of the binary solvent system. Same silica particles (27
nm diameter) as used hereinabove were dispersed in two
different binary solvent systems by replacing 2,6-lutidine
with 2,5-lutidine and 2,4-lutidine. The SeedGel embodiment
formation was observed with the corresponding gel transi-
tion temperature at 7° C. and 17° C., respectively due to the
fact that changing solvent isomers shifted the bulk phase
temperature of the corresponding binary solvent system. The
sample prepared with 2,5-lutidine at the gel transition tem-
perature (7° C.) was found to have lower scattering intensity
due to the fact that the formed domain size was too large,
outside of the q-range accessible by USANS. The tunability
of gelation temperature greatly expands the applications of
the composition for the SeedGel embodiment by designing
its structure and property response to external stimuli at will.
Any suitable binary solvent system as disclosed hereinabove
may be used, depending upon particular application requir-
ing particular gelation temperature or requiring transition to
gelation upon cooling or heating.

Controlling Optical Properties of the SeedGel
Embodiment

[0110] The optical properties of SeedGel embodiment can
also be controlled by adjusting the refractive index between.
the particle domain and solvent domain. In the exemplary
composition for the SeedGel embodiments, the refractive
index of 2,6-lutidine (n=1.497) and silica (n=1.46) are both
larger than that of water (n=1.33). Hence, when the tem-
perature of the exemplary composition of the SeedGel
embodiment is increased, the particle domain loses 2,6-
lutidine while the solvent domain gains 2,6-lutidine because
2,6-lutidine is less soluble in water at higher temperatures.

Sep. 28, 2023

Consequently, the refractive index of the particle domain
decreases and that of the solvent domain increases without
the change of particle domain structures. At a certain tem-
perature. the two domains are optically indistinguishable,
but a domain size of a few micrometers still persists. The
transparency to light provides opportunities for optically
triggered reactions to occur within the bicontinuous chan-
nels that are difficult to be achieved by many other gel
systems with micrometer sized domains. As a result, the
SeedGel embodiment sample was found to be initially turbid
at the gelation transition temperature of about 26° C., but it
slowly became transparent at about 29° C.

[0111] This thermally reversible transparent SeedGel
embodiment can also be obtained at various particle con-
centrations. In an embodiment, an exemplary composition
for the SeedGel embodiment comprising water/2,6-lutidine
as binary solvent system may comprise nanoparticles in an
amount of such as 16.5%, 19.6%, and 21.7% by volume
based on the total volume of the composition. This is due to
the fact that the refractive index of the particle domain and
the solvent domain is close to each other as a result of
relative partition of lutidine in both domains. The finely
adjustable optical property is thermo-reversibly driven by
the solvent phase separation. Bijel samples and many other
gel systems with micrometer sized domains are usually
turbid. The formation of the transparent particle gel with
micrometer sized bicontinuous domains introduces new
opportunities for exemplary SeedGel embodiments to many
light sensitive applications, such as sensors or transparent
bicontinuous mold/micro-reactors for inducing photo-cross-
linking of other materials.

[0112] In conclusion, SeedGel embodiment can be real-
ized by tuning nanoparticle surface to be strongly favored by
one component of a binary solvent system and no net
attraction exists between particles in the liquid state. It
shows excellent thermal reversibility, precise structural
reproducibility, and tunable domain sizes at micrometer
length scales. SeedGel embodiment is extremely versatile
and is demonstrated here to work with different particle sizes
and have a large range of adjustable gelation temperatures
One amazing property of the SeedGel embodiment is its
tunability of the refractive index of different domains that is
tough to achieve by physical gel systems with micrometer
sized domains. As majority of colloidal particles are aqueous
based, SeedGel embodiment provides an alternative route to
achieve bicontinuous structures for many water-soluble par-
ticles that do not form Bijel. Thus, SeedGel embodiment
complements Bijel systems and greatly extends the appli-
cations of bicontinuous structures formed by colloidal self-
assembly. As the gel formation is initiated by the local
binary solvent system phase separation, it is expected that
this is a general approach that has potential to work with
many different types of particles. Future works will be
needed to evaluate its applications with other type of par-
ticles and binary solvent systems.

Supplementary Note 1-1: The Teubner-Strey Model
for the Ultra-Small Angle Neutron Scattering
(USANS) Fitting to Obtain the Domain Size

Information

[0113] ‘Teubner-Strey model is widely used to fit the
bicontinuous structure of a two-component system. The
USANS scattering intensity was modeled using the corre-


US 2023/0305289 Al

closely placed thermocouple near the sample cell. A constant
temperature of 27.4° C. was maintained for at least 20 min
before imaging a sample. The temperature control was
achieved with an accuracy of +0.1° C. by circulating fluid
with an external thermal bath. Image acquisition was
achieved with a scanning area of 127.8 ymx127.8 4m by
collecting fluorescence light from 576 nm to 700 nm that
emanated from the sample. Zen Blue (Zen 2.5 System) was
used for the data collection. And Image J was used for the
image processing.

SAXS and WAXS.

[0193] Both the SAXS and WAXS measurements were
performed on 9-ID beamline at Advanced photon source
(APS) of Argonne National Laboratory (Lemont, IL, US). A
q-range of 0.07 A~'<q<6 A~! was realized by stitching the
SAXS and USAXS results together. The energy of the X-ray
beam used in the experiment was 21 keV. The temperature
was controlled by Linkam (Tadworth, UK) THMS600 con-
troller. Irena macro based on Igor package was used to
analyze the data.

UV-Vis Spectroscopy

[0194] A Thermo Scientific Evolution 201 UV-VIS Spec-
trometer (Waltham, MA, US) was used to record the optical
transmission spectrum as a function of temperature. A
cuvette with a pathlength of 1 mm was utilized. The tem-
perature was precisely controlled by a Peltier element con-
nected to a thermal bath. The temperature was equilibrated
for at least 15 min before each measurement. A Cary 5000
(Agilent, Santa Clara, CA, USA) spectrometer was utilized
to extend the measurement to near infrared range.

Zeta Potential Measurement

[0195] Zeta potential measurements using Zetasizer were
performed on the silica particles dispersed in water, which is
closely related to how repulsive the particles are in the
solvent. The measurements were done in both 10 nm and 27
nm particles dispersed in pure water. The concentrations of
particles were both at 1% by volume. For each particle, the
measurements were repeated three times. For 10 nm par-
ticles, the results are shown below:

[0196] | zeta_1=-31.029.2 mV:
[0197] | zeta_2—33.3210.7 mV;
[0198] zeta_3—32.8211.2 mV.

[0199] For 27 nm particles, the zeta potential of the three

measurements are shown below:

[0200] zeta_1—38.4228.2 mV;
[0201] | zeta_2—40.0229.6 mV;
[0202] | zeta_3—-37.3228.6 mV.

1. A composition comprising:

an effective amount of nanoparticles dispersed homoge-
neously in a binary-solvent system comprising a first
solvent and a second solvent, the binary solvent system
being a single-phase, in a liquid state at or below a first
temperature;

wherein the nanoparticles have a preferential wettability
to the first solvent,

wherein the composition is disposed, upon changing from
the first temperature, to transition thermo-reversibly
from the liquid state to a gel state,

wherein the gel state comprises bi-continuous domains
including a particle domain and a solvent domain, and

Sep. 28, 2023

wherein the particle domain comprises nanoparticles dis-
persed in a first-solvent-rich fraction of the binary
solvent system and the solvent domain comprises a
second-solvent-rich fraction of the binary solvent sys-
tem,

2. The composition of claim 1, wherein size of each of the
particle micro-domain and the solvent micro-domain is
dependent upon a temperature ramping rate of the thermo-
reversible transition of the composition from the liquid state
to the gel state.

3. The composition of claim 2, wherein each of the
particle micro-domain and the solvent micro-domain have a
different refractive index dependence on wavelength, and
wherein the refractive index of the particle micro-domain
matches with that of the solvent micro-domain for an
identified wavelength at an identified temperature, whereby
the composition becomes transparent to the identified wave-
length at the identified temperature.

4. The composition of claim 3, wherein the composition
in the gel state has tunable wavelength-dependent properties
for a range of wavelengths as a function of temperature.

5. The composition of claim 4, wherein the wavelength-
dependent properties comprise one or more of: scattering
and transmittance.

6. The composition of claim 3, wherein the wavelength is
in the range of 200 nm to 2400 nm.

7. The composition of claim 1, wherein the binary solvent
system comprises one of the following mixtures of solvents:

(i) water, deuterated water, or partially deuterated water
and methylpyridine, dimethyl pyridine, deuterated or
partially deuterated methylpyridine, deuterated or par-
tially deuterated dimethylpyridine, or isomers thereof;

(ii) water and methyl ethyl ketone;

(iiijan alcohol and an alkane;

(iv) ethylene carbonate and p-xylene;

(v) ethylene glycol and nitromethane; or

(vi) cyclohexane and nitromethane.

8. The composition of claim 1, wherein the nanoparticles
have an average particle diameter in the range of from 5 nm
to 100 nm.

9. A device comprising the composition of claim 1

10. The device of claim 9, wherein the device is selected
from a filter, a temperature sensor, a smart window, a smart
display, a battery, or a tissue growth scaffold.

11. A method of dynamically tuning radiation transmis-
sion comprising:

(i) providing the composition of claim 1 in the gel state,

and

(ii) changing a temperature of the composition to thermo-
reversibly modify peak radiation transmission at a first
wavelength at a first temperature to a second wave-
length at a second temperature.

12. A method of thermo-reversibly controlling operation

of a filter, the method comprising:

(i) providing a filter having the composition of claim 1 in
a liquid state;

(ii) adjusting the temperature ramping rate of the thermo-
reversible transition of the composition from the liquid
state to the gel state, to thereby control operation of the
filter.

13. The method of claim 12, comprising operating the

filter to selectively filter or block radiation.

14. The device of claim 12, wherein the filter has a pore
size defined by the two micro-domains, the method com-


US 2023/0305289 Al

ture change induces local phase separation of the two
solvent molecules in the vicinity of the particles, which
introduces an effective attraction between particles. Further
heating up the sample increases the attraction strength
between particles so that the nanoparticles percolate through
the system to form a gel with bicontinuous domains. With
different wavelength dependences of the refractive index for
each domain, the refractive index of these two domains are
only matched at a specific wavelength. The light with the
wavelength close to the matched wavelength is allowed to
pass through the sample while all other light is scattered
away and cannot pass through the sample. By changing the
temperature, the solvent composition in both domains can be
exchanged, resulting in the change of refractive index of
each domain and the shift of the light wavelength that can
match the refractive index between two domains. The shift
of the matched wavelength as a function of temperature thus
offers the control of the wavelength of light that can pass
through the sample. As the phase separation temperature can
be adjusted by using different binary solvents, the gelation
transition temperature can be tuned. Hence, the working
temperature range for a sample for the light transmission can
be controlled.

[0016] According to an aspect of the present invention,
disclosed herein is a method and a class of material for
generating structural color that can be used in many fields.
Structural color is widely observed in nature and is known
to be non-fading, environmental-friendly and exhibit a broad
range of coloration. It is of great interest to explore new
approach that is economical and scalable. The fast and
sensitive response of the SeedGel embodiments of the
present invention directly makes the material a temperature
sensor to detect subtle temperature changes. The transmis-
sion of the light/heat can be dynamically changed in
response to the temperature variation during the day. It can
‘smartly’ monitor the temperature of a confined space with-
out additional input of electricity by switching off the heat
flow beyond a certain point. Importantly, this transition
temperature can be adjusted at will

[0017] Disclosed herein is a method to realize structural
color with dynamic tunability in the SeedGel embodiments
of the present invention ina bottom-up approach. In embodi-
ments of the present invention, tunability does not originate
from size change of the structures, but from wavelength
selective scattering based on refractive index matching by
binary solvents. High color clarity is demonstrated and the
temperature range for color transition can be customized. It
is a general mechanism that allows large scale processability
ina broad range of fields, including optics, displays, sensors,
filters, and smart windows.

[0018] In an aspect of the present invention, there is
provided a composition comprising an effective amount of
nanoparticles dispersed homogeneously in a binary-solvent
system comprising a first solvent and a second solvent, the
binary solvent system being a single-phase, in a liquid state
at or below a first temperature;

[0019] wherein the nanoparticles have a preferential
wettability to the first solvent,

[0020] wherein the composition is disposed, upon
changing from the first temperature, to transition
thermo-reversibly from the liquid state to a gel state,

[0021] wherein the gel state comprises bi-continuous
domains including a particle domain and a solvent
domain, and

Sep. 28, 2023

[0022] wherein the particle domain comprises nanopar-
ticles dispersed in a first-solvent-rich fraction of the
binary solvent system and the solvent domain com-
prises a second-solvent-rich fraction of the binary sol-
vent system. In an embodiment, the step of changing
the temperature of the composition from the first tem-
perature comprises heating the composition above the
first temperature. In another embodiment, the step of
changing the temperature of the composition from the
first temperature comprises lowering the temperature of
the composition below the first temperature.

[0023] In an embodiment, the size of each of the particle
micro-domain and the solvent micro-domain is dependent
upon a temperature ramping rate of the thermo-reversible
transition of the composition from the liquid state to the gel
state.
[0024] In yet another embodiment, each of the particle
micro-domain and the solvent micro-domain have a different
refractive index dependence on wavelength, and wherein the
refractive index of the particle micro-domain matches with
that of the solvent micro-domain for an identified wave-
length at an identified temperature, whereby the composition
becomes transparent to the identified wavelength at the
identified temperature

[0025] In yet another embodiment, the composition in the

gel state has tunable wavelength-dependent properties for a

range of wavelengths as a function of temperature, wherein

the wavelength-dependent properties comprise one or more
of: scattering and transmittance. The wavelength can be in
the range of 200 nm to 2400 nm.

[0026] In an embodiment, the binary solvent system of the

said composition comprises one of the following mixtures of

solvents:

[0027] @) Water, deuterated water, or partially deuter-
ated water and methylpyridine, dimethyl] pyridine, deu-
terated or partially deuterated methylpyridine, deuter-
ated or partially deuterated dimethylpyridine, or
isomers thereof;

[0028] (ii) water and methyl ethyl ketone:
[0029] (iii) an alcohol and an alkane;

[0030] (iv) ethylene carbonate and p-xylene;
[0031] _(v) ethylene glycol and nitromethane; or
[0032] (vi) cyclohexane and nitromethane.

[0033] The binary solvent system of alcohol and alkane
may include any suitable alkane such as, methanol, ethanol,
and propanol. Suitable alcohols include, but are not limited
to pentane, hexane, heptane, octane, nonane, decane, unde-
cane, and dodecane. In an embodiment, the binary solvent
system may comprise:
[0034] (i) methanol, deuterated methanol, or a partially
deuterated methanol, and
[0035] (ii) hexane, deuterated hexane, or a partially
deuterated hexane.

[0036] In another embodiment, the binary solvent system
may comprise:
[0037] (i) ethanol, deuterated ethanol, a partially deu-

terated ethanol, and

[0038] (ii) dodecane, deuterated dodecane, or a partially

deuterated dodecane.

[0039] In In an embodiment, the nanoparticles have an
average particle diameter in the range of from 5 nm to 100
nm or from 7 nm to 75 nm, or from 8 nm to 50 nm. In
another embodiment, the nanoparticles are charged silica
nanoparticles, having an average particle diameter of about


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US 2023/0305289 Al

[0164] Additionally, the color range of transmission can
be customized to meet the requirement of specific applica-
tions across a wide temperature range. FIG. 10A shows the
transmission measurement at different temperatures. By
using a binary solvent system of water/2,4-lutidine, the
transition temperature can be shifted to below 20° C. The
solvent pair of water/3-methylpyridine increases the tem-
perature transition range to close to 50° C.

EXPERIMENT NO. 5: EXAMPLES OF
SHIFTING COLOR TRANSITION RANGE
USING DIFFERENT SOLVENT PAIRS IN

SEEDGEL EMBODIMENT

[0165] In this experiment, different solvent pairs were
used to achieve different color transition temperatures. A
wide color transition range is demonstrated herein with three
solvent pairs: water/2,4-lutidine, water/3-methylpyridine,
water/deuterated 3-methylpyridine, and water/2-methylpyri-
dine. Same Ludox® TM as used hereinabove was used. The
composition preparation procedure remained the same, but
the concentration of both the nanoparticles and the solvents
were different in this experiment. Here, 300 ul of 2.4-
lutidine, 400 ul of 3-methylpyridine, or 400 ul deuterated
3-methylpyridine, or 400 ul 2-methylpyridine are mixed
with 1 ml Ludox® TM to achieve different color transition
temperatures. Each sample went through vortex and rolling
to ensure a good mixing of the different components.

[0166] By using different solvent pairs, the color transition
temperature can be customized at will. A wide range of
transition temperatures for tunable light transmission can be
designed to meet the requirements of specific applications.
By using a binary solvent system of water/2,4-lutidine, the
transition temperature can be shifted to below 20° C. The
solvent pair of water/3-methylpyridine increases the tem-
perature transition range to between 40° C. and 50° C. It is
important to point out that by replacing 2,4-lutidine with
3-methylpyridine, not only the transition temperature is
increased, the temperature range for color transition is also
widened.

[0167] It was observed that the solvent deuteration also
affects the color transition temperature of the sample. FIG.
12 shows a SeedGel embodiment of another exemplary
composition comprising a binary solvent system of water!
deuterated 3-methylpyridine. The color transition tempera-
ture was found to increase by about 20° C. With deuterated
solvents, the temperature that produces transmission peak at
400 nm is shifted up from ~40° C. to ~60° C. So, the
temperature range that the sample showed color transition is
between 60° C. and 80° C. Compared to water/hydrogenated
3-methylpyridine, the temperature range becomes even
broader in the binary solvent system of water/deuterated
3-methylpyridine. It is also interesting to observe in FIG. 12
that the wavelength of the transmission peak started to shift
back towards the short wavelength side above 80° C. with
the binary solvent system of water/deuterated 3-methylpyri-
dine.

[0168] The color transition temperature can be raised even
higher if the solvent pair of water/2-methylpyridine is used.
The results in FIG. 13 shows that the onset of the color
transition temperature can be increased from 60° C. to 75°
C. Similar to what has been observed in other solvent pairs,
the transmission peak shifis towards longer wavelength by
increasing the temperature from 75° C. to 98° C.

Sep. 28, 2023

EXPERIMENT NO. 6: DEMONSTRATION OF
TUNABLE STRUCTURAL COLOR IN A
DIFFERENT SYSTEM WITH THE SAME

MECHANISM,

[0169] In an aspect, there is a method of tuning radiation
transmission comprising providing a composition compris-
ing microparticles dispersed in a binary solvent system,
wherein a refractive index of the binary solvent system is
close to that of the plurality of microparticles. The method
further comprises tuning the transmission of radiation
through the composition by changing a solvent fraction of
the two solvents of the binary solvent system. The micropar-
ticles and the binary solvent system present in the compo-
sition are chosen such that they have different dependence of
their respective refractive index on wavelength. Addition-
ally, the refractive index of the microparticles matches with
that of the binary solvent system at certain compositions of
the binary solvent system.

[0170] In an embodiment of the method, the binary sol-
vent system comprises toluene and n-hexane. In another
embodiment, the binary solvent system comprises a first
solvent present in an amount of 45 to 65%, by weight, based
on the total weight of the binary solvent system. In an
embodiment, the microparticles have an average particle
diameter in the range of from 1 pm to 12 um.

[0171] In an aspect, an exemplary composition comprises
a silica microsphere dispersion in a binary solvent system
was used. The size of silica particles was in the range of 1
tum-12 um (Cospheric LLC). The binary solvent system
consisted of toluene and n-hexane was used as a solvent. The
particle surface was coated with dimethylpolysiloxane, so
that it was wettable by organic solvent with a low polarity.
By mixing toluene with n-hexane, the refractive index of the
solvent can be shifted at different volume fractions. A range
of toluene concentration between 39% and 58% was used.

The silica particle concentration was 50 mg/ml. Thus, FIG.
14 shows transmission of the exemplary composition at
different solvent fractions.

[0172] The systematic study clearly demonstrates that the
color transition range can be designed over a wide range of
temperatures. It is also important to note that this technology
does not just work for SeedGel embodiment formed with
nanoparticles. Both the solvent pair and the particles can be
replaced at the same time. A new system that shows the color
transition based on the same mechanism is made possible by
using microspheres dispersed in a binary mixture of toluene
and n-hexane. The sample is in a liquid state. A smaller
toluene amount resulted in the transmission of short wave-
length and more toluene in the solvent led to a shift of the
transmission peak to longer wavelength. This experiment
provides evidence that the mechanism we proposed to
explain the color transition in SeedGel embodiment is valid.
It also offers opportunity to control the light transmission in
a completely different system (liquid dispersion in organic
solvents) without gel formation.

[0173] In an aspect, there is provided a device comprising
the composition, as disclosed hereinabove. In an embodi-
ment, the composition comprises nanoparticles and the
composition transitions from liquid state to a gel state upon
changing temperature from a first temperature. In an
embodiment, the step of changing the temperature of the
composition from the first temperature comprises heating
the composition above the first temperature. In another
embodiment, the step of changing the temperature of the


US 2023/0305289 Al

tures, but only blue light (short wavelength) is permitted at
lower temperatures. A temperature below the gelation point
(26° C.) reverts the SeedGel embodiment of the exemplary
composition back to the liquid state (20° C.), making it
transparent to all visible light. This was further confirmed by
a broadband transmission (not shown). Therefore, the col-
oration is not a result of absorption or luminescence of the
chemical species (silica, water, 2,6-lutidine) in the SeedGel
embodiment of the composition. Rather, it is the structures
formed within the composition that is responsible for this
modulated wavelength control.

Temperature-Dependent Wavelength Modulation

[0147] In an embodiment, each of the particle micro-
domain and the solvent micro-domain have a different
refractive index dependence on wavelength, and wherein the
refractive index of the particle micro-domain matches with
that of the solvent micro-domain for an identified wave-
length at an identified temperature, whereby the composition
becomes transparent to the identified wavelength at the
identified temperature.

[0148] In another embodiment, the composition in the gel
state has tunable wavelength-dependent properties for a
range of wavelengths as a function of temperature, wherein
the wavelength-dependent properties comprise one or more
of: scattering and transmittance. The wavelength can be in
the range of 200 nm to 2400 nm.

[0149] The UV-VIS transmission of the SeedGel embodi-
ment of the exemplary composition, as shown in FIG. 7 was
found to be consistent with FIG. 6 with respect to the same
trend observed at various temperatures. At relatively low
temperatures (26° C.~27° C.), short wavelengths of light
(below 400 nm) are transmitted through the SeedGel
embodiment of the exemplary composition, while those with
longer wavelengths are scattered away. By ramping up the
temperature, the transmission peak shifts towards longer
wavelength. A decrease in transparency across all wave-
lengths is observed by further increasing the temperature to
28.8° C. The well-defined peak suggests that it is possible to
achieve high precision wavelength selection by temperature.
Additionally, as shown in FIG. 8, an increase in the path
length from 1 mm to 10 mm of the SeedGel embodiment of
the exemplary composition, resulted in a dramatic reduction
in the full width at half maximum (FWHM) of the trans-
mission peak to 44 nm. Furthermore, not only in the visible
range, the transmission in the infrared range up to 2500 nm
can be tuned as well, as shown in FIG. 9. The control over
the infrared range is extremely useful for managing heat
transfers. The optical property of SeedGel embodiment can
be applied to stimuli-responsive smart windows/optical fil-
ters. The thermally reversible liquid-gel transition makes it
simple to install and readily adaptable to curved surface.

[0150] A series of experiments were thus designed to
characterize the structure of the sample in order to unveil the
physical mechanism. In literature, a preferential scattering/
reflection of visible light (structural color) is commonly
believed to be related to certain repeating distance. The
tunability comes from the change of that distance. There-
fore, three possible hypotheses need to be validated that may
be accountable for the wavelength-selective transmission.
Those include: 1. Whether repeating structures exist in the
range comparable to the wavelength of visible light (380

Sep. 28, 2023

nm-740 nm); 2. Do particles pack into crystalline domain
with long range order; 3. If liquid crystal is formed with
solvent molecules.

[0151] The scattering profiles of the SeedGel embodiment
of the exemplary composition within the temperature range
(27° C. and 30° C.) exhibiting tunable structural color
characterized by neutron (USANS/SANS) and X-ray scat-
tering (SAXS/WAXS) over a wide q-range spanning five
orders of magnitude, from 3x10-° A“! to 6 Av!. This
corresponds to structure size from angstrom level to ~20 um
that includes all the relevant sizes. Ultra-small angle neutron
scattering (USANS) and small angle neutron scattering
(SANS) were used to characterize micrometer domains,
particle packing and shape of individual nanoparticles.
Domain size was found to be on the order of a few
micrometers (peak at q=1.7x10~* A~') and the interparticle
distance was ~30 nm (peak at q=0.023 A~'). Neither of them
changes with temperature between 27° C. and 30° C. that
shows tunable transmission. A q-* decay is observed
between 1.7x10~* A“! and 0.023 AW’, indicating a smooth
interface. This also suggests that no repeating distance
appears with a length scale that is comparable to the wave-
length of visible light. The uncorrelated structure-property-
relationship in large length scale motivated further investi-
gations in smaller distances. However, the broad peak at
0.023 Av suggests random packing of nanoparticles, which
is also irresponsive to temperature change. Scattering results
from a collimated synchrotron beam confirms the SANS
results that nanoparticles do not crystallize. Still, no corre-
lation between temperature and structure change can be
inferred from small angle X-ray scattering (SAXS) and
wide-angle X-ray scattering (WAXS) results. Solvent mol-
ecules are not organized into liquid crystals, since only
broad peaks appear down to angstrom level. In comparison
to the widely used methods to control structural color or
select light transmission with a size change, the results from
the SeedGel embodiment of the present composition point
towards a completely new mechanism to realize dynami-
cally controlled coloration.

[0152] Due to the scattering length density (SLD) differ-
ences between each component, neutron and X-ray are much
more sensitive to silica nanoparticles over binary solvent
systems. To light, the contrast comes from the different
refractive index in the system. Different from X-ray and
neutron, the refractive index of lutidine is comparable to that
of silica and is higher than that of water. Therefore, wave-
length dependent refractive index of the bicontinuous
domains was investigated. The binary solvent systems
dynamically exchange in response to temperature change.
Contrast matched SANS experiments revealed the compo-
sitions of lutidine and water in each domain. The weight
fraction of lutidine in the particle domain was found to
decrease from 15% at 27.5° C. to less than 10% at 30°C. A
reduction of lutidine in particle domain suggests an increase
of its concentration in solvent domain due to mass balance.
The wavelength dependent refractive index of both domains
could be calculated using Lorentz-Lorenz formula based on
composition of particles and solvents. It was found that the
two domains show similar refractive index, but different
wavelength dependence. At a given temperature, contrast
between bicontinuous structure disappears for short wave-
length of light (~400 nm), where the refractive index is
‘matched’. Ramping up the temperature reduces the lutidine
ratio in the particle domain, thus the refractive index, and


Patent Application Publication Sep. 28, 2023 Sheet 6 of 14 US 2023/0305289 Al

Silica
~~ Gel A00%
Liquid af

Precipitate F 90

“canditions. for,
-bicontindous...°
. Structure *

© Lutidine


Patent Application Publication

Sep. 28, 2023 Sheet 5 of 14

12 q Contrast Matched
1st 2nd
10¢ ° A “sS 20°C
) O 30°C
BE
S 6
4-
DE
0
0.001
60 No Contrast Match
50/ 1st 2nd
° A = 20°C
40k Sanaa Oo oO 30°C
ZF 307 8 ant:
20; banal
10+ E
ar ay a a a
0.001 0.01 ' 0.1
q(A’)

FIG. 4B

US 2023/0305289 Al


US 2023/0305289 Al

30 nm or about 27 nm, and the silica nanoparticles are
dispersed in an amount of 5% to 50%, or 7.5% to 45%, or
9% to 30%, by volume in the binary solvent system of water
and/or partially deuterated water, and methylpyridine. deu-
terated methylpyridine, partially deuterated methylpyridine,
dimethyl pyridine, deuterated dimethylpyridine, partially
deuterated methylpyridine, and/or their isomers, based on
the total volume of the composition.

[0040] In another aspect, there is provided a device com-
prising the said composition. The device can comprise a
filter, a temperature sensor, a smart window, a smart display,
a battery, or a tissue growth scaffold.

[0041] In an aspect, there is provided a method of dynami-
cally tuning radiation transmission comprising providing the
composition, as disclosed hereinabove, in the gel state, and
changing a temperature of the composition to thermo-
reversibly modify peak radiation transmission at a first
wavelength transmissivity from having high transmissivity
at a range of wavelength at a first temperature to having a
second wavelength transmissivity less than the first trans-
missivity at a second temperature. The range of the wave-
length with high transmissivity can be adjusted by tempera-
ture.

[0042] In another aspect of the invention, there is provided
method of thermo-reversibly controlling operation of a filter,
the method comprising providing a filter having the com-
position, as disclosed hereinabove, in a liquid state and
adjusting the temperature ramping rate of the thermo-revers-
ible transition of the composition from the liquid state to the
gel state, to thereby control operation of the filter. In an
embodiment, the method comprises operating the filter to
selectively filter or block radiation.

[0043] Inn embodiment, the filter has a pore size defined
by the two micro-domains, the method comprising tuning
the pore size by controlling the size of the two micro
domains by adjusting the temperature ramping rate.

[0044] In another embodiment, the method comprises
operating the filter to selectively filter or block a component
of a fluid. The fluid may comprise a solid/liquid system,
solid/gas system, or a liquid/liquid system.

[0045] In an aspect, there is a method of tuning radiation
transmission comprising:

[0046] (i) providing a composition comprising
microparticles dispersed in a binary solvent system,
wherein a refractive index of the binary solvent system
is close to that of the plurality of microparticles, and

[0047] (ii) tuning the transmission of radiation through
the composition by changing a solvent fraction of the
two solvents of the binary solvent system,

wherein the microparticles and the binary solvent system
have different dependence of their respective refractive
index on wavelength, and

wherein the refractive index of the microparticles matches
with that of the binary solvent system at certain composi-
tions of the binary solvent system.

[0048] In an embodiment of the method, the binary sol-
vent system comprises toluene and n-hexane. In another
embodiment, the binary solvent system comprises a first
solvent present in an amount of 45 to 65%, by weight, based
on the total weight of the binary solvent system. In an
embodiment, the microparticles have an average particle
diameter in the range of from 1 wm to 12 jum.

Sep. 28, 2023

BRIEF DESCRIPTION OF THE DRAWINGS.

[0049] FIG. 1A: Schematic illustration of a Bijel (Prior
art) utilizing particles that wet both solvents equally (dif-
ferent solvent regions are defined by colors).

[0050] FIG. 1B: Schematic illustration of an exemplary
composition for a SeedGel embodiment, which relies on
favorable wetting of particles to one component of a binary
solvent. Due to this surface wettability difference, particles
in Bijel are jammed at the interface and SeedGel embodi-
ment confines particles within one of the solvent regions.
[0051] FIG. 2A: A 3-D confocal image of a SeedGel
embodiment with a total z-stack of 40 um. Note that the
scale bar is based on the size in the x-y plane.

[0052] FIG. 2B: A ultra-small angle neutron scattering
(USANS) pattern of the gel structure of the SeedGel
embodiment at different temperatures by cooling a compo-
sition from a gel state (30° C.) (SeedGel embodiment) to a
liquid state (20° C.). By fitting the USANS patterns with the
Teubner-Strey model, the averaged domain size can be
obtained. The error bars in the figures represent one standard
deviation and are often smaller than the symbol size.
[0053] FIG. 2C: A small angle neutron scattering (SANS)
pattern of the gel structure of the SeedGel embodiment at
different temperatures by cooling a composition from a gel
state (SeedGel embodiment) (30° C.) to a liquid state (20°
Cc)

[0054] FIG. 2A: A SANS profile of a thermo-reversible
SeedGel embodiment of a composition A prepared with 27
nm particles cycling between liquid state (20° C.) and gel
state (30° C.). Composition A comprises a specially
designed mixture of H,O and D,O to contrast match the
scattering length density of water phase to that of silica. The
error bars represent one standard deviation and are often
smaller than the symbol size.

[0055] FIG. 3B: ASANS profile ofa composition B which
uses normal water (HO) so that silica particles are still
visible to neutrons when engulfed by water. The error bars
represent one standard deviation and are often smaller than
the symbol size.

[0056] FIG. 3C: A schematic illustration of the case of
scattering length density (SLD) of water matched to that of
silica as in composition A, corresponding to FIG. 3A.
[0057] FIG. 3D: A schematic illustration of the case of
SLD of water not matched to that of silica as in Composition
B, corresponding to FIG. 3B.

[0058] FIG. 4A: Thermo-reversible SeedGel embodiment
prepared with 10 nm particles and different binary solvents
probed by SANS and USANS. The SLD of water phase is
matched to that of silica. The error bars represent one
standard deviation and are often smaller than the symbol
size.

[0059] FIG. 4B: Thermo-reversible SeedGel embodiment
prepared with 10 nm particles and different binary solvents
probed by SANS and USANS. The SLD of water phase is
not matched to that of silica. The error bars represent one
standard deviation and are often smaller than the symbol
size.

[0060] FIG. 5: A schematic illustration of a phase diagram
of an exemplary SeedGel embodiment. The compositions of
all components in the system are weight fractions over the
total mass. The circular open symbols represent conditions
that can result in thermo-reversible SeedGel embodiment.
The square open symbols indicate regions that are in the
liquid state at room temperature but do not gel when heated


Patent Application Publication Sep. 28,2023 Sheet 8 of 14

Normalized Transmission

1.0

0.8

0.6

0.4

0.2¢

US 2023/0305289 Al

courant

600 800

1000

Wavelength (nm)
FIG. 7
100
= 80-
8
< 60-
Ss
€ 40
g
© :
= 20).
0 Sow

Wavelength (nm)

FIG. 8

400 500 600 700 800


US 2023/0305289 Al

position too. As the peak at 30° C. slightly shifts to high-q
position compared to that at 20° C, and the packing of
particles is different in the liquid state from that in the gel
state, both the form factor and structure factor have different
values at 20° C. and 30° C. Taking the ratio of sample A and
B, shown in Eq-3, removes the change of both the form
factor and the structure factor due to slight change of the
q-position of the scattering peak at those two temperatures.
Ap is the SLD difference between silica particles and its
surrounding solvent in each temperature. @punidines and
Pnarchedwaters We the Volume fractions of lutidine and water
in the total sample volume, respectively. @ruriaines and
Pnarcheawarer, €€ the Volume fraction of hutidine and water
in the particle domain, respectively. The intensity of the
peaks was known from experiment and SLD was calculated
based on chemical formula and density. The volume fraction
of lutidine and water was determined to be 10.4% and 89.6%
in the particle domain.

Supplementary Note 1-4: USANS Patterns of a
Sample to Demonstrate the Thermal
Reproducibility, the Long-Time Stability, and
Domain Size Tunability

[0118] Two USANS patterns at 30° C. were measured
after cycling the temperature through 4° C. The USANS
patterns were found to be completely identical, indicating
that the domain structures are precisely reproducible when
quenching rate is the same. Additionally, the USANS pat-
terns of the exemplary composition in the gel state (at a fixed
temperature of 30° C.) as a function of time were measured.
The USANS data did not show any change for the exem-
plary composition in the gel state at a constant temperature
for at least 20 hours, demonstrating that the domain structure
is stable for at least 20 hours without aging effect.

[0119] Overall, SeedGel embodiment which is the gel
state of the composition is thermally reversible with great
structural reproducibility and stability.

EXPERIMENT NO. 2: CONTROLLING
DOMAIN SIZE AND SIZE DISTRIBUTION OF
BICONTINUOUS STRUCTURES OF THE
SEEDGEL EMBODIMENT

[0120] As disclosed hereinabove, in order to prepare a
SeedGel embodiment, nanoparticles need to be dispersed in
a binary solvent system in its single-phase region. The
exemplary composition disclosed hereinabove was tested
for SeedGel embodiment formation at about 27.4° C. The
formed gel had strong mechanical strength that allowed a
flip-vial test, where the gel retained its form when the vial
was flipped upside down. Rhodamine B was used as a dye
that is known to favorably partition into the 2,6-Iutidine rich
solvent domain so that a picture of the bicontinious struc
ture could be taken by a confocal microscope. Those bicon-
tinuous micrometer domains were clearly visible under a
confocal microscope. FIG. 3D schematically illustrates the
structure of SeedGel embodiment with alternating particle
domains and solvent domains. One important parameter to
characterize the domain structure is the average distance
between neighboring particle domains, or the periodicity (d)..
The periodicity can be also considered as the summation of
the average channel widths of both the particle (Lp) and
solvent domains (Ls). Those dimensions will be discussed in
later sections. It is important to note that the domain size is

Sep. 28, 2023

widely used in Bijel to describe the channel width of
bicontinuous structures. The term “domain size” is used here
to describe the channel width of SeedGel embodiment.

Controlling Domain Size by Nanoparticle
Concentration

[0121] As nanoparticle concentration and solvent compo-
sition are both important for the SeedGel embodiment
formation, it is crucial to obtain a complete and quantitative
picture of their effects on the domain size structure of the
bicontinuous system. As disclosed hereinabove, the period-
icity of a SeedGel embodiment is in the range of a few
micrometers. Thus, ultra-small angle neutron scattering
(USANS) is an ideal tool that provides quantitative structure
characterization in the right length scale. Consequently, a
series of four different compositions for SeedGel embodi-
ment comprising nanoparticle concentrations of 16.5%,
17.9%, 19.6%, and 21.7% by volume, based on the total
volume of the composition, were prepared at a fixed 2.6-
lutidine weight fraction and their corresponding gel struc-
tures were investigated with USANS. All four compositions
were in the liquid state at room temperature and became
SeedGel embodiments at 30° C. The USANS scattering
patterns (not shown) of these four compositions at 30° C.
showed that at intermediate particle volume fraction of
17.9%, the formed SeedGel embodiment showed a relatively
well-defined peak with a very flat low-q scattering curve.
This is a typical scattering pattern for a bicontinuous struc-
ture. The flat curves at low-q with a well-defined scattering
peak indicate a relatively well-defined repeating distance of
bicontinuous structures. By slightly increasing particle vol-
ume fraction from 17.9% to 19.6%, the peak position was
shifted to a higher q-value, which means that the inter-
domain distance in these SeedGel embodiment samples
became smaller. Thus, within a certain range, increasing the
nanoparticle concentration decreases the periodicity. Teub-
ner-Strey model was used to fit the experimental data to
obtain the periodicity of the bicontinuous structures. The
detailed description of the model and the fitting results can
be found in the Supporting Note 2-1 and Table $2-1. The
periodicity of the domains was found to decrease from 12.6
ym to 2.68 um by simply increasing the particle volume
fraction by 1.7%. At this concentration range, the q-depen-
dence in the high-q range follows

Note that the USANS has a slit smearing function that
affects the q-dependence. After desmearing, the true q-de-
pendence follows Porod’s law, i...

1
g

This indicates that the interface between the particle domain
and solvent domain is relatively sharp and smooth.

[0122] Further reducing the nanoparticle volume concen-
tration to 16.5% disturbed the repeatability of the domain
size. A hump was observed between 2x10~' A“! and 3x10~
A“, while the low-q scattering intensity kept increasing


as) United States

US 20230305289A1

a2 Patent Application Publication 1) Pub. No.: US 2023/0305289 Al

Xi et al.

(54) METHOD TO THERMO-REVERSIBLY
CONTROL LIGHT AND HEAT FLOW WITH
BICONTINUOUS MICRO-DOMAIN

(71) Applicants:University of Delaware, Newark, DE
(US); Government of the United
States of America, as represented by
the Secretary of Commerce,
Gaithersburg, MD (US)

(72) Inventors: Yuyin Xi, San Jose, CA (US); Yun Liu,
Gaithersburg, MD (US)

(73) Assignees: University of Delaware, Newark, DE
(US); Government of the United
States of America, as represented by
the Secretary of Commerce,
Gaithersburg, MD (US)

(21) Appl. No.:  18/017,106

(22) PCT Filed: Jul. 27, 2021

(86) PCT No.: PCT/US2021/070989
$371 (©),
(2) Date: Jan, 20, 2023

Related U.S. Application Data

(60) Provisional application No. 63/056,794, filed on Jul
27, 2020, provisional application No. 63/171,139,
filed on Apr. 6, 2021

(43) Pub. Date: Sep. 28, 2023
Publication Classification

(51) Int. Ch

GO2B 26/00 (2006.01)

CO9K 9/00 (2006.01)
(52) US. CL

CPC wisenes GO2B 26/004 (2013.01); CO9K 9/00

(2013.01); B82¥ 20/00 (2013.01)

(57) ABSTRACT

A dynamically tunable composition, a device including the
composition, a method of dynamically tuning radiation
transmission through the composition, and a method of
thermo-reversibly controlling operation of a filter formed
from the composition. The composition includes a plurality
of nanoparticles dispersed in a single phase region of a
binary solvent systems composed of a first solvent and a
second solvent, the nanoparticles having a preferential wet-
ability to the first solvent. Changing temperature of the
composition causes it to transition thermo-reversibly from
the liquid state to a gel state having bi-continuous domains,
including a particle domain and a solvent domain. The
particle domain features nanoparticles dispersed in a first-
solvent-rich fraction of the binary solvent system, and the
solvent domain is a second-solvent-rich fraction of the
binary solvent system. Exemplary devices incorporating the
composition include a filter, a temperature sensor, a smart
window, a smart display, a battery, and a tissue growth
scaffold.



Patent Application Publication Sep. 28, 2023 Sheet 11 of 14 US 2023/0305289 Al

1000

800

FIG. 10B

600
Wavelength (nm)

400

} L i
© jon) © © ©
jan) foe) © ws N
—

(%) eoueyIWSUeL] PEZI|EWJON



Patent Application Publication Sep. 28, 2023 Sheet 10 of 14 US 2023/0305289 Al

FIG. 10A

Wavelength (nm)

OQ ©
=) ce)
bard

(%) SOUBYIWSUPI] PSZI|EUUON



US 2023/0305289 Al

Supplementary Note 3-3: Calculation of Light
Transmission Based on Refractive Index of Both
Domains

[0157] Based on the refractive index obtained from the
previous section, the light transmission can be calculated
based on Equation 20. Here, the absorption of the light from
the system is not considered because none of the compo-
nents absorbs light in the visible range (FIG. 29). The
transmitted intensity of light (I) can be related to the incident
intensity (I,) with the scattering cross section (£) and
pathlength (d). The scattering cross section is proportional to
contrast ((Ap)*) between the particle and solvent domains.
‘A’ is a constant value that is related to the concentration,
volume, form factor, structure factor of the bicontinuous
domain that do not change with temperature. Here, a fixed
value of 5.24x10"! A? is used for ‘A’ to result in a reasonable
transmission range between 0 and 1. A pathlength of 1 mm
is used for the calculation if not specified. The contrast term
can be calculated using the refractive index of the particle
domain (n,) and the solvent domain (n,), as well as the
wavelength of the light (A) in Equation 21.

oY ge o-taehad 20

om 2) ~ "

¥ (2) +2

ny

[0158] The gradual change of the relative refraction index
of the two domains due to temperature increase leads to
partial matching of the two domains at short wavelength
(low temperatures) to partial matching at long wavelength
(high temperatures), The calculated light transmission was
plotted in the same figure. It is clear from the data that the
wavelength with the closest refractive index between the
two domains show the largest light transmission. Other
wavelengths of light are scattered away. By increasing the
temperature, lutidine is driven out from the particle domain
to the solvent domain. As a result, the refractive index of the
particle domain is reduced and that of the solvent domain is
increased because the refractive index of lutidine is higher
than both domains. As the two domains show different
wavelength-dependent refractive index change (different
curvatures), only a small portion of the wavelength can be
transmitted through the sample. Since this wavelength selec-
tion is purely due to scattering, the pathlength can be used
to better define the full width at half maximum (FWHM) of
the transmitted light. is a demonstration of the change of the
FWHM by increasing the thickness of the sample. The
transmitted light could confine the bandwidth from above
100 nm to only 44 nm.

Supplementary Note 3-4: Static Light Scattering
Measurement Confirms the Wavelength Dependent
Dynamical Matching of the Refractive Index
Between Particle and Solvent Domains

[0159] Static light scattering measurement was conducted
on a gel sample within the temperature range that shows
color transition with a 532 nm laser. The flat scattering curve
of the solvent mixture (lutidine and water) at different
temperatures indicate that the solvent mixture itself does not

Sep. 28, 2023
17

form structures in the length scale corresponding to this
q-range. In contrast, the gel sample with silica nanoparticles
exhibit a dramatic increase of the scattering intensity at 27°
C. Further increasing the temperature reduces the scattering
intensity. At 28.6° C., the scattering intensity comes back up.
This is consistent with the proposed mechanism that the
exchange of lutidine between the particle and solvent
domain leads to a wavelength-dependent refractive index
change. The strong scattering at 27° C. is due to the large
size of the bicontinuous micro-meter domains. Further
increasing the temperature reduces the refractive index
difference between the two domains, where a reduction of
the scattering intensity at low-q is observed. The transmis-
sion of 532 nm light through the exemplary composition is
sharply increased at 28.1° C. Further increasing the tem-
perature moves the refractive index matched point to a
longer wavelength, thus improving the contrast between the
two domains.

EXPERIMENT NO. 4: CUSTOMIZABLE COLOR
TRANSITION RANGE

[0160] In an aspect, there is provided a method of dynami-
cally tuning radiation transmission comprising providing the
composition, as disclosed hereinabove, in the gel state, and
changing a temperature of the composition to thermo-
reversibly modify peak radiation transmission at a first
wavelength transmissivity from having high transmissivity
at a range of wavelength at a first temperature to having a
second wavelength transmissivity less than the first trans-
missivity at a second temperature. In an embodiment, the
composition in the gel state has tunable wavelength-depen-
dent properties for a range of wavelengths as a function of
temperature. In an embodiment, the step of changing the
temperature of the composition comprises heating the com-
position. In an embodiment, the step of changing the tem-
perature of the composition comprises cooling the compo-
sition.

[0161] As shown in FIG. 6D, a display was placed on the
other side of the SeedGel embodiment sample, with the
experimental set as shown in FIG. 6B. The word “Seed” was
in red color and the word “Gel” was in blue color. At low
temperature (20° C.), the sample is in the liquid state, where
no large structures are formed, both red and blue light can
transmit through the sample and visible by eyes. This
indicates that the dynamically tunable transmission was
made possible by the structures formed in the sample, rather
than due to the chemical components in the sample that
either absorb or emit light. At high temperature (close to 29°
C), the sample allows red light to pass through, but block
out the blue light. Slightly cooling down the sample, while
still in the gel state. the sample allows blue light to pass
through without permitting the red light.

(0162] The transmitted and scattered light showed
complementary colors. At the temperature when transmitted
light is yellow, the scattered light is blue. The same obser-
vation goes for a different temperature that the scattered light
is yellow when the transmitted light is blue. The only
difference between the two pictures is temperature. The
picture on the right is taken with a lower temperature.
[0163] The exemplary composition for the SeedGel
embodiment is very sensitive to temperature change. A
slight change of temperature by only 0.1° C. could lead to a
peak shift of more than 10 nm of the peak of the transmitted
light.


US 2023/0305289 Al

increases that in the solvent domain. Consequently, the
narrow band with ‘matched’ refractive index shifts towards
longer wavelength. Based on the calculation, a combined
change of only 0.007 in refractive index was enough to shift
the transmission peak across the whole visible range. The
rest of the light that could ‘view’ both micrometer domains
experience strong scattering due to micrometer domains,
which is responsible for the colorful scattered light as shown.
in FIG. 6. Based on the lutidine ratio extrapolated from
contrast matched SANS experiment, a temperature change
from 30° C. to 27.5° C. would result in a refractive index
difference of ~0.0135, which is more than enough to shift the
transmitted light from blue to yellow. The calculated trans-
mission by slightly varying the relative refractive index
between the two domains to simulate the effect of tempera-
ture change. The peak in transmission was found to be
closely correlated to the matched refractive index between
the two domains. An increase in temperature leads to a red
shift of the transmitted light, which is consistent with the
experimental results in FIG. 7. This proposed mechanism is
further corroborated by static light scattering experiments
with a 532 nm laser. The contrast was greatly reduced to a
minimum at 28.1° C., which confirms that the solvent
exchange between the two domains driven by temperature
change results in partial refractive index matching.

[0153] Based on this mechanism, longer pathlength expo-
nentially increases the scattering of light, which explains the
better defined FWHM of transmitted light in FIG. 8. The A
narrow bandwidth is usually preferred to avoid crosstalk
between different colors. The achieved 44 nm FWHM in
FIG. 8 is comparable to that of quantum dots.

[0154] Inconclusion, anew mechanism to achieve tunable
light scattering and transmission is proposed from disor-
dered material with micro-meter domains. The modulation
of the optical properties originates from temperature depen-
dent miscibility of a binary solvent system, rather than the
size change of structures. The material described here is
‘smart’ with two-folds of tunability. Its transmitted light
wavelength is adjustable by temperature change and the
temperature transition point can be customized at will. The
controllable wavelength for the SeedGel embodiment of the
exemplary embodiment is broad in range and narrow (pre-
cise) in bandwidth (44 nm) at a given temperature. Its
mechanism for tunable optical property opens a door to a
new library of materials that can be used for photonic
devices, including smart windows, optical fibers, sensors
and memories. A new material design guideline is proposed
that light modulation can be realized by domains with
different refractive index dependence on wavelength. There
is no requirement for the shape of the domain, given it is
large in size that can strongly scatter light. The mechanism
discussed here could be extended to porous materials by
refilling a partially miscible binary liquid.

Supplementary Note 3-1: Evidence from SAXS
Measurement Rules Out the Possibility of
Crystalline Arranaement of Particles

[0155] Photonic crystals are known to scatter certain
wavelength of the visible light that is related to its lattice
parameter. Typically, an ordered close packing with an
interparticle distance of a few hundred nanometers (compa-
rable to the wavelength of light) is used in the photonic
crystals. Thus, a characterization of particle packing is rather
important in shining light to the mechanism for the tunable

Sep. 28, 2023

optical transmission. Small angle X-ray scattering (SAXS)
measurement with a pinhole collimation was thus con-
ducted. The results were consistent with the SANS results.
The peak within this q-range represents a uniformly distril
uted particle distance with short-range order. The inter-
particle distance corresponds to a length scale of ~30 nm.
However, no sharp peak was observed in the probed q-range,
indicating that the nanoparticles do not form long range
order (crystals). The mechanism of the tunable transmission
and scattering of light originates from a disordered structure.

Supplementary Note 3-2: Calculation of the
Wavelength Dependent Averaged Refractive Index
of Both the Particle and Solvent Domain

[0156] In order to calculate the averaged refractive index,
the composition of each component in both of the domains
need to be measured. The SANS profiles of a composition
with scattering length density (SLD) of water contrast
matched to that of the silica were measured by adjusting the
volume ratio of H,O and D,O to 42:58. In the gel state, the
nanoparticles are jammed within particle domain that is rich
in water because the particle surface is highly charged and
hydrophilic. As the water phase is contrast matched to that
of silica, the scattering intensity of the interparticle peak is
reduced when the gel is formed. This reduction is in com-
parison to the sample at 20° C. when the solvent molecules
are miscible. In the liquid state (20° C.), the contrast comes
from the difference of SLD between silica and solvent
mixture that contains lutidine. Higher temperature drives
lutidine away from the particle domain, further lowering the
structure factor peak for the sample at 30° C. compared to
that at 27.5° C. In contrast, the peak intensity remains almost
constant for the sample with ‘unmatched’ water phase. The
ratio of the peak intensity of the ‘matched’ and ‘unmatched’
sample at the same temperature could be used to estimate the
weight fraction of both water and lutidine in both particle
and solvent domains. The detailed description of the method
is presented in our previous publication. (1) It is calculated
that in the particle domain, the weight fraction of lutidine
could decrease from 15.3% to 9.7% when the temperature is
increased from 27.5° C. to 30° C. The concentration of
lutidine in the solvent domain can be inferred using mass
balance. The amounts of different components in both
domains are listed in Table S4-1. It is important to note that
the fraction of each component is normalized to the total
mass of solvent in each domain. In this temperature range,
the concentration of silica nanoparticles in the particle
domain does not change and is fixed at a volume fraction of
39.1%. This is suggested by the unchanged structure factor
peak of SANS at varied temperatures.

TABLE S4-1

The calculated weight percentage of lutidine
and water in both particle and water domain.

Particle Domain Solvent Domain

Lutidine (%) Water (%) Lutidine (%) Water (°%)
25°C. 153 847 41.6 58.4
30.0° C. 97 90.3 413 52.7



Patent Application Publication Sep. 28, 2023 Sheet 7 of 14 US 2023/0305289 Al

Scattering Mode Transmission Mode
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US 2023/0305289 Al

with USANS, as shown in FIG. 2B and (SANS, as shown in
FIG. 2C. These scattering patterns are dominated by silica
particles since the scattering contrast between silica particles
and the solvent is much larger than that between water and
2,6-lutidine. By analyzing the temperature-dependent scat-
tering patterns, particle structures and gel transition tem-
perature can be determined.

[0101] The gel state (above 26° C.) of the exemplary
composition is indicated by a scattering peak at ~1.7x10-*
A“ in USANS patterns, as shown in FIG. 2B due to the
repeating distance between the tortuous particle domains.
Reasonably good fit is achieved with the Teubner-Strey
model that is widely used to describe the scattering pattern
of a bicontinuous structure. (See Supplementary Note 1-1
and Supplementary Table 1-1 for details.) A particle domain
size of about 2 jm was obtained for the SeedGel embodi-
ment of this composition with the solvent channel size at
around 1 jum at 30° C. consistent with the result of the
microscope image shown in FIG. 2A. The solvent channel
size can even reach sub-micrometer dimensions, which is
comparable to the smallest achievable domain size of Bijel
system, schematically shown in FIG. 1A. The gel sample of
the exemplary composition consists of two tortuous
domains: the particle domain that contains concentrated
particles, and the solvent domain that is made of a mixture
of water and 2,6-lutidine, as illustrated in FIG. 1B. It should
be noted from FIG. 2B that the bicontinuous structure of the
gel sample does not change between 30° C. and 27° C. as
USANS peak position does not shift in this temperature
range.

[0102] The gelation temperature of this particular exem-
plary composition was observed to be around 26° C., which
is 8° C. lower than the phase separation temperature of the
bulk binary solvent system of about 34° C. This is expected
as the gel transition is initiated by the attraction between
nanoparticles due to the local phase segregation of the
binary solvent system.

[0103] Water and 2,6-lutidine are miscible at low tempera-
tures below the critical temperature at about 34° C. of the
bulk binary solvent system. Due to the charge repulsion,
charged silica nanoparticles are stable in this binary solvent
system when it is far away from the gelation temperature.
The silica particles are highly charged and have a strong
affinity to water over 2,6-lutidine. At elevated temperatures,
but before reaching the critical point of the bulk binary
solvent system (34° C.), the development of a water-rich
layer around particles introduces a solvent triggered attrac-
tion between particles. This attraction increases as the sys-
tem gets close to the gelation temperature, which will
eventually dominate the interaction between particles as
previously demonstrated. The solvent-induced attraction
drives aggregation, and ultimately the SeedGel embodiment
formation by forming two distinct bicontinuous domains:
one particle domain with particles closely packed within the
water-rich solvent, and one solvent domain rich in 2,6-
lutidine without particles.

[0104] It was found that around the gel transition tem-
perature of the exemplary composition, the particle domain
size increases to approximately 7 jum due to the weakened
strength of gel resulting in the coarsening of domains.
Further cooling down the sample wipes out the scattering
peak at low-q region, resulting in the thermo-reversible
transition from gel to liquid. In complement to USANS
results, SANS patterns were obtained to investigate the local

Sep. 28, 2023

structures of assembled particles upon cooling. In compari-
son to a broad inter-particle structure factor peak in the
liquid state, a much sharper peak at slightly larger q-position
appeared in the gel state, indicating that particles are packed
much denser in the gel state with smaller average inter-
particle distance. The particle local volume fraction in the
particle domain was determined to be about 39% in the gel
state by fitting the SANS patterns. (See Supplementary Note
1-2 for details.)

[0105] A wide range of temperature ramping rates were
used to form gel even as low as 0.1° C./min, as discussed
hereinbelow, which is in sharp contrast to the fast quenching
required by many Bijel systems

[0106] In the gel state of the exemplary composition, the
binary solvent system also separates into two solvent regions
commensurate with the observed bicontinuous structure: the
water rich solvent region overlapping with the particle
domain, and the lutidine rich solvent region coinciding with
the solvent domain. Specially designed SANS experiments
were used to probe the solvent separation. Two compositions
were prepared with the same particle and lutidine concen-
tration, which were named as composition A and composi-
tion B. In the composition A, the SLD of water was tuned to
match that of particles, by mixing H,O and D,O with the
volume ratio at 48:52, while the composition B was prepared
with normal water (HO) as a reference. Their SANS results
at different temperatures are shown in FIGS. 2A and 3B,
respectively. In the liquid state (20° C.), both samples
showed a peak at q=0.016 Av! due to the inter-particle
structure factor. However, in the gel state, the peak intensity
for the composition A shows a sharp intensity drop by more
than 5 times while that of composition B remains about the
same as that in a liquid state. This difference of the relative
change of the intensity in a gel state observed in FIGS. 2A
and 3B was solely due to the solvent composition difference.
For the composition A, the scattering intensity drops since
the solvent surrounding particles is rich in matched water.
And there is no contrast between the matched water and
particle in a gel state, ie., silica particles become almost
invisible as schematically illustrated in FIG. 2C. In com-
parison, particles are visible in both liquid and gel states for
the sample B prepared with normal water (H,O), as sche-
matically illustrated in FIG. 2D. These results thus indicate
that the particles in the gel state are fully engulfed by the
water rich solvent. The scattering peak does not compietely
disappear in FIG. 2Aas the water rich solvent region still has
small amount of lutidine as expected for a binary solvent
system phase separation. The relative volume fraction in the
water rich solvent region was estimated to be approximately
90% of water and 10% lutidine with a significant decrease
of lutidine concentration from the nominal concentration of
30% volume fraction. (See Supplementary Note 1-3 for
details.) The formed gel is thus indeed a SeedGel embodi-
ment with particle and solvent partition schematically illus-
trated in FIG. 1B.

[0107] The formed gel was found to have excellent
thermo-reversibility, precise structural reproducibility, sta-
bility, and tunability. The same samples in FIGS. 2A and 3B
were measured twice by cycling the temperature between
20° C. and 30° C. The SANS scattering patterns together
with the USANS results shown in Supplementary Note 1-4
were found to be completely identical at the same tempera-
tures in gel states. Thus, both the local and large domain
structure are not only thermally reversible, but also precisely


US 2023/0305289 Al

attraction introduced by solvent fluctuation between par-
ticles is reasonably strong to cause the particle aggregation.
Further increasing the temperature leads to the SeedGel
embodiment formation with particle domains percolating
throughout the whole sample volume. This is indicated by
the Porod’s law behavior with a q~* decay at the low-q
range.

[0136] Additionally, the USANS experiments during
gradual cooling of SeedGel embodiment showed that the
domain size remains the same at temperatures about one
degree higher than the gelation point. but it slowly changes
when the final temperature is very close to the gelation
temperature. To clearly understand this structure change at
the transition point, controlled experiments were conducted.
In particular, USANS data of SeedGel embodiment formed
with a final temperature close to the gelation temperature
(about 26° C.) was compared to that produced with a much
higher final temperature (30° C.). A slow ramping rate (0.1°
C./min) was used to avoid the decrease of the ramping rate
close to the final temperature due to the PID control loop
since the gelation temperature (26° C.) was set as the final
temperature in this experiment. The sample was fully regen-
erated by dissolving the gel structure at 20° C. before
quenching to different final temperatures to eliminate the
process history. All the smeared USANS results showed a
slope of —3, meaning that a smooth interface between the
two domains was observed. It was found that the peak shifts
to a lower q-value around the transition point (26° C.),
suggesting that a final setting temperature close to the
gelation point could increase the size of the bicontinuous
channels. The periodicities obtained with the Teubner-Strey
model fitting were consistent with the trend observed before,
the size increases from approximately 6 um (30° C.) to 8 um
(26° C.). by quenching the sample right to gelation tem-
perature. Hence, the final quenching temperature close to the
gelation point could be applied to a composition if a larger
domain size is preferred. Also, the exemplary composition
showed excellent reproducibility at both temperatures, as
indicated by the spot-on USANS profiles for repeated mea-
surements at the same condition (not shown).

[0137] In conclusion, one can control the domain size and
the size distribution of bicontinuous structures through par-
ticle concentration, solvent composition, temperature ramp-
ing protocol, and final temperature for the SeedGel embodi-
ment preparation. Combined USANS and SANS analysis
provide a quantitative description of the structure over a
wide range of length scales. ‘Optimal’ concentrations are
identified for both particle and 2,6-lutidine concentrations to
realize well-repeating bicontinuous domains in a SeedGel
embodiment. Within the ‘optimal’ range, a higher particle
concentration leads to a decrease of periodicity, Higher or
lower concentrations outside the ‘optimal’ range induce a
wider distribution of the domain sizes. A schematic phase
diagram is thus provided that can benefit the production of
SeedGel embodiment. Interestingly, although particle con-
centration and 2,6-lutidine ratio can effectively tune the
domain structure, a similar densely packed local particle
structure is observed for SeedGel embodiments with differ-
ent compositions. Ramping rate is another effective way to
control the size of the bicontinuous structure. An empirical
linear relationship is extrapolated between the domain size
and the logarithm of the ramping rate. Slow ramping rates
would lead to the formation of large periodicity. Large

Sep. 28, 2023

domain structure can also be reproducibly formed with a
final temperature close to the gelation temperature.

Supplementary Note 2-1: Description of the
Teubner-Strey Model and Summary of Fitting
Results

[0138] Bicontinuous structures have been widely
described with the Teubner-Strey model. This model has
been previously implemented to successfully fit the micro-
domains of SeedGel embodiment. A detailed description of
the model and how the domain size is obtained is explained
herein above in Supplementary Note 1-1. In brief, correla-
tion length (€) and periodicity (d) are used to model the
scattering profile. The mathematic expressions are listed
from Equation 16 to Equation 19 as follows.

Brgy (1 - gap) col 16
apt ag + erg"

I@=

[0139] Where @, represents volume fraction of one of the
domains, Ap is the contrast term that is equal to the
scattering length density (SLD) difference between the two
domains, Three parameters (i.e. periodicity (d), correlation
length (@), and scale) are left as variables with the rest terms
fixed as constant values during the model fitting.

[0140] The obtained sizes are listed in Table $2-1 and the
fitting results demonstrates that the q-dependence of the
scattering curve follows Porod’s law,

after desmearing.

[0141] To show the wide channel size distribution of the
scattering curves with the low-q upturn, two sample com-
positions are chosen as examples to fit with a model of
combining two Teubner-Strey models together. The fitting
results of this model indicate that one domain size is not
enough to explain our scattering data. And there should be
a wider distribution of the domain size. The upturn of the
very low-q intensity is due to the emergence of larger
domains in addition to the smaller domains (averaged close
to 3 um). The relative volume fraction ratios of the domains
are obtained and shown in Table S2-2 based on the assump-
tions that both the particle volume fraction and solvent
compositions in particle domains remain the same every-
where. It is noted that even though the fitting agrees with the
experimental results very well. the fitting results are biased
by the proposed model. It could be possible that the distri-
bution of the domain size may have more than two domi-
nating values. However, this requires introducing more
fitting parameters to fit the data. The current proposed model
has the minimum number of parameters needed to fit the
data. And its fitting results already support the conclusion


Patent Application Publication Sep. 28, 2023 Sheet 3 of 14 US 2023/0305289 Al

5
10 @ 30°C
4 m 29°C
10 Fy A 28°C
v 27°C
3h < 26°C
_ 10 $ ae O 25°C
S { Oo 24°C
= ,.2 2 % 23°C
4 %

0 * =X 22°C

4 <

10 >

2 4 2 4. 2 4
0.001 0.01 0.1

q(A”)

FIG, 2C


Patent Application Publication Sep. 28, 2023 Sheet 14 of 14. US 2023/0305289 Al

100
& 80- a 22.8°C
8 759°C
© 60- .
£ 87.7°C
5 40-
¢
g
KF 90-

@) L Ll H L
400 600 800 1000
Wavelength (nm)
FIG. 13
100

S 80

5 00f// 2X

= we,

B 40H) iio

S fie Silica (1-12ym)

2 z — Toluene+n-Hexane

F 20 ” Toluene Volume Ratio

— 39% —= AA pwn 4B py -nenes 48 %
es eee 53 Y-v-— 56 % ---- 58

400 600 800 1000
Wavelength (nm)

FIG. 14



US 2023/0305289 Al

demonstrations. Whereas a strong attractive force between
particles is needed for previous systems, the particles in a
SeedGel embodiment have a net repulsion or no attraction
between them in liquid states. In addition, SeedGel embodi-
ment formation is driven by the local phase separation of
solvents while the bulk solvent phase separation is required
in the intraphase gelation of the previous Bijel systems.

These distinctions provide SeedGel embodiments with
many unique and interesting properties. The structural arrest
of particles in one solvent domain of a SeedGel embodiment
leads to the gel formation with great reversibility, reproduc-
ibility, scalability, and tunability. Compared to Bijel, Seed-
Gel embodiments provide an alternative way to arrest bicon-
tinuous structures by removing the often non-trivial surface
treatment of particles, reducing the rigid requirement of fast
quenching rate by orders of magnitude, allowing adjustable
gelation temperature and domain size, and can easily incor-
porate particles as small as 10 nm. In addition, the use of the
binary solvent offers SeedGel embodiments a unique oppor-
tunity to tune the optical property that is not achievable by
many other gel systems.

[0010] In a composition for the SeedGel embodiment,
particles interact with a repulsive potential in the liquid state
far away from the gel transition temperature so that the
formed SeedGel embodiment can thermo-reversibly change
from liquid state to gel state, and vice versa. By increasing
the temperature, the solvent fluctuation induced attraction
becomes larger. At a high enough temperature, the particles
in a SeedGel embodiment are assembled by the attraction
induced by local solvent phase separation due to preferential
wetting of the particle surface by one component of the
binary solvents. This SeedGel embodiment is thus driven by
the local solvent segregation that results in a gelation
transition temperature much lower than the critical tempera-
ture of the binary solvent. Hence, the quenching temperature
can be set in the single-phase region of the binary solvent
system before reaching the critical point of the binary
solvent. Besides, the SeedGel embodiment enables quasi-
static ramping and promises large-scale processability. A
slow temperature ramping of SeedGel embodiment forma-
tion renders more opportunities to engineer the bicontinuous
structures. It should be noted that this is different from some
other attempts to jam particles in either binary solvents or
polymer systems, for which there is a strong attraction
between particles.

[0011] In an aspect of the present invention, a SeedGel
embodiment formation is demonstrated hereinbelow using
exemplary compositions with charged silica nanoparticles in
the water/lutidine binary solvent. Additionally, disclosed
herein are the factors controlling the domain structure of the
SeedGel embodiment system, including but not limited to,
particle concentration, solvent composition, temperature
ramping rate, quenching depth of the final temperature. The
phase diagram of the exemplary composition for the Seed-
Gel embodiment formation is also disclosed hereinbelow.
Without wishing to be bound by any particular theory, it is
believed that these results will help to optimize the experi-
mental conditions to achieve the desired bicontinuous struc-
tures of SeedGel embodiment systems for different applica-
tions.

[0012] Disclosed herein is a novel solvent segregation
driven gel (SeedGel embodiment) comprising bicontinuous
structures with excellent thermal structural reversibility and
reproducibility, tunable domain size, adjustable gel transi-

Sep. 28, 2023

tion temperature, and amazing optical properties. It is
achieved by trapping nanoparticles into one of the solvent
domains upon the phase separation of the binary solvent.
Due to the universality of the solvent driven particle phase
separation, SeedGel embodiment is thus potentially a
generic method for a wide range of colloidal systems.

[0013] Another aspect of the present invention, includes a
new method to efficiently control the flow of visible light
and heat (infrared radiation) through the control of the
solvent distribution in a new colloidal gel, which is made of
nanoparticles with a binary solvent. The properties of mate-
rials prepared with this method are thermo-reversibly con-
trollable through temperature. The light transmission is
tunable over a wide range of wavelength, from ultraviolet
(~200 nm) to infrared (~2400 nm). As a consequence, the
color of the materials is also adjustable by temperature. The
working temperature range can be adjusted at will by tuning
the solvent properties. And the process is economical and
scalable. Thus, it is an excellent candidate for climate
adaptive building shells to passively manage daytime light
without requiring additional energy input, for smart filters to
select wavelength favorable for crop growth in green houses,
and for shields of automobiles to avoid unwanted overheat-
ing. Additionally, it can be used as a thermochromic material
for temperature sensor as well.

[0014] Another aspect of the invention includes a method
and related materials for thermo-reversibly manipulating the
transmission of light/heat over a wide range of light wave-
length (200 nm to 2400 nm), realized by the structural
arrangement of the binary solvent in a SeedGel embodi-
ments. The solid framework of the colloidal gel provides a
platform to stabilize a unique and tunable structure of the
relative distribution of the two components of the binary
solvent. This method, and consequently its applications,
arise from structures formed by the binary liquid, as com-
pared to mainstream techniques that realize structural color
with solid building blocks. Unlike thermochromic liquid
crystal, the liquid structure of SeedGel embodiments is
amorphous and no ordered liquid molecule packing is
observed. The material exhibits ‘smart’ color change in
response to the temperature without additional energy input.
The temperature change is rapid and sensitive that the
transmission could be altered within a couple tenth of a
degree. As the light manipulation is originated from scat-
tering of the structure, this new type of material is inherently
resistive to the light-induced degradation commonly seen in
pigments or dyes. The stimuli-responsiveness and the ability
that allows temperature range customization make it a
versatile method to achieve ‘smart’ control of light for a
variety of applications.

[0015] The mechanism for filtering light/heat is due to the
different wavelength dependence of the refractive index of
two micrometer-sized domains, a particle micro-domain and
a solvent micro-domain, formed in the SeedGel. The refrac-
tive index of each domain is adjusted by the temperature, as
the temperature can alter the solvent composition in each
domain without affecting the domain structures. The change
of the solvent composition in each domain can be reversibly
controlled by the temperature. Exemplary compositions
comprising silica nanoparticle dispersion in a partially mis-
cible binary solvent system, such as water/lutidine, are used
herein to demonstrate the feasibility of this method. The
particles are tuned so that they are preferentially wetted by
one of the components in the binary solvent. The tempera-


Patent Application Publication Sep. 28, 2023 Sheet 2 of 14 US 2023/0305289 Al

FIG. 2A

(q)



US 2023/0305289 Al
11

without a flat region at low-q. This suggests that a larger
domain size starts to develop. And the periodicity has a
much broader distribution for the sample at 16.5% particle
volume fraction. Hence, the domain size has a much wider
range of distribution (Table $2-2 in the Supporting Note 2-1
for detailed discussion). By increasing the particle concen-
tration to 21.7%, the domain size distribution also becomes
larger. Therefore, at a constant 2,6-lutidine ratio, the particle
concentration needs to be carefully adjusted to achieve the
desired structures. For some applications, the well-defined
channel (domain) size, as manifested as a better-defined
periodicity, may be desirable. However, for other applica-
tions, the random distribution of the channel size could be
preferred. Here, the interest is in identifying the conditions
to optimize the SeedGel embodiment with a well-defined
domain size. Consequently, the ‘optimal’ sample condition
is at an intermediate range of particle concentrations. Too
large or too small of the particle concentration would
broaden the distribution of the domain sizes. Within the
‘optimal’ range of sample conditions with ordered repeating
distance, a higher volume fraction is found to reduce the
periodicity of the domains.

Controlling Domain Size by Binary Solvent
Composition

[0123] Besides the particle concentration, the 2,6-lutidine
weight fraction is another important parameter that can be
used to tune bicontinuous structures. USANS measurements
were performed on SeedGel embodiment of the exemplary
compositions prepared with different 2,6-lutidine concentra-
tions at 30° C. while fixing the particle to water ratio at a
constant value. Notably, the particle concentration used here
corresponds to a volume fraction of 13.7%, which is much
smaller than the concentration (about 24%) used in an
exemplary composition disclosed hereinabove in the
Example 1 with a lower 2,6-lutidine ratio.

[0124] Similar to what was observed by varying the par-
ticle concentrations, it was found that an optimum solvent
composition (weight fraction of 37.2% in the exemplary
binary solvent system) is important in realizing bicontinuous
structures with well-defined repeating distance. This is evi-
denced by an obvious hump in the USANS scattering profile
with a flat low-q scattering intensity (not shown). By fitting
the results with the Teubner-Strey model, a periodicity of
2.65 jum was obtained (Table $2-1 in the Supporting Infor-
mation). Compared to the scattering profile at ‘optimal’
2,6-lutidine weight fraction of 37.2%, a higher or lower
solvent ratio led to an increase in scattering intensity at the
low-q range, which extended outside the USANS window.
This suggests that for a fixed particle concentration, there
exists an ‘optimal’ solvent composition to obtain a well-
defined repeating distance. A deviation from the ‘optimal’
solvent composition increases the randomness of the domain
size distributions with a substantial increase of the fraction
of large domains.

[0125] Additionally, the resulting SeedGel embodiment of
the compositions with varying amounts of 2,6-lutidine were
characterized by small angle neutron scattering (SANS). It
was observed that a higher 2,6-lutidine ratio greatly
increases the scattering intensity at low-q (q<0.01 A~'),
which is consistent with the USANS experiments that sol-
vent composition could considerably affect the domain
structure. It is interesting to note that although the large
micro-domain structure was found to be sensitively affected,

Sep. 28, 2023

the local packing of the particles as indicated by the inter-
particle distance peak remained almost unchanged. This
suggests that the local particle packing in the particle
domain is not affected in the gel state. Within the particle
domain, the particles are uniformly and closely packed with
an estimated volume fraction of around 40%. There are still
some slight differences in the structure factor peak of the
SANS data. At relatively low 2,6-lutidine ratios (25.8% and
28.8%), the peaks were identically sharp and located at
about 0.023 A~!. By significantly increasing the 2,6-lutidine
concentration (weight fraction of 31.4%) to the limit at this
particle concentration, the interparticle distance peak
became slightly broader and its position shifted to about
0.022 A-'. This indicates that the local particle concentra-
tion is slightly reduced and the interparticle spacing
becomes a little larger.

[0126] Thus, both the 2,6-lutidine ratio and silica particle
concentration need to be adjusted in order to form bicon-
tinuous structures with the domains having a well-defined
repeating distance.

[0127] With detailed discussions on how the concentration
of each component affects both the periodicity of the micro-
domain and local nanoparticle packing distance within the
particle domain, it is useful to summarize the compositions
compatible with SeedGel embodiment formation ina ternary
phase diagram. It could be used as a design guideline to
engineer the domain structures and benefit future SeedGel
embodiment preparations. In the ternary phase diagram
shown in FIG. 5, all concentrations were converted to
weight fractions over the total mass of the exemplary
composition. The region that leads to thermo-reversible
SeedGel embodiment is schematically shaded in grey.
Whether a gel is formed or not was judged by a vial flipping
test. The solid line indicates the ‘optimal’ conditions that
would result in bicontinuous structures with well-defined
inter-domain spacing. A quantitative analysis of the bicon-
tinuous structures with USANS suggests that the composi-
tions along the green line result in similar averaged period-
icity of about 3 pm (2.62 um, 2.68 um, 2.65 um, 2.68 pm,
and 2.97 ym). Along the solid line, the particle volume
fraction could be reduced to 9.8% by properly increasing the
2,6-lutidine ratio (Table S2-1 in the Supporting Informa-
tion). As discussed already, a wide distribution of the
domain size is formed in the gel state in the grey region
outside the ‘optimal’ conditions. As a rule of thumb, an
increase in particle concentration would require a decrease
in the 2,6-lutidine ratio for SeedGel embodiment formation.
[0128] If the concentrations of both silica particles and
2,6-lutidine are too high in a sample (i.e. moving upper right
away from the grey region in the phase diagram), increasing
the temperature does not cause gelation. Instead, silica
particles usually precipitate even at low temperatures
because the kinetics of the aggregation formation is so fast
that the precipitation occurs before the percolation.

[0129] Without wishing to be bound by any particular
theory, it is believed that using colloidal particles with the
density closer to the binary solvent system, the area of the
SeedGel embodiment formation in the phase diagram could
potentially be extended to a much larger region than what is
identified in the exemplary composition. On the other hand,
by reducing the concentrations of particles and 2,6-lutidine
simultaneously (i.e. moving bottom left away from the grey
region in the phase diagram), a liquid state sample can be
formed at room temperature, but do not percolate to form a


Patent Application Publication Sep. 28, 2023 Sheet 1 of 14 US 2023/0305289 Al

FIG. 1A (Prior Art)

100

FIG. 1B


US 2023/0305289 Al

composition from the first temperature comprises lowering
the temperature of the composition below the first tempera-
ture. In another embodiment, the composition comprises
microparticles and the composition does not undergo gel
transition. The device can comprise a filter, a temperature
sensor, a smart window, a smart display, a battery, or a tissue
growth scaffold.

[0174] In another aspect of the invention, there is provided
method of thermo-reversibly controlling operation of a filter,
the method comprising providing a filter having the com-
position, as disclosed hereinabove, in a liquid state and
adjusting the temperature ramping rate of the thermo-revers-
ible transition of the composition from the liquid state to the
gel state, to thereby control operation of the filter. In an
embodiment, the method comprises operating the filter to
selectively filter or block radiation.

[0175] Inn embodiment, the filter has a pore size defined
by the two micro-domains, the method comprising tuning
the pore size by controlling the size of the two micro
domains by adjusting the temperature ramping rate.

[0176] In another embodiment, the method comprises
operating the filter to selectively filter or block a component
of a fluid. The fluid may comprise a solid/liquid system,
solid/gas system, or a liquid/liquid system.

[0177] As used herein, when an amount, concentration, or
other value or parameter is given as either a range, preferred
range, or a list of upper preferable values and lower pref-
erable values, this is to be understood as specifically dis-
closing all ranges formed from any pair of any upper range
limit or preferred value and any lower range limit or
preferred value, regardless of whether ranges are separately
disclosed. Where a range of numerical values is recited
herein, unless otherwise stated, the range is intended to
include the endpoints thereof, and all integers and fractions
within the range. It is not intended that the scope of the
invention be limited to the specific values recited when
defining a range.

[0178] Within this specification, embodiments have been
described in a way which enables a clear and concise
specification to be written, but it is intended and will be
appreciated that embodiments may be variously combined
or separated without departing from the invention. For
example, it will be appreciated that all preferred features
described herein are applicable to all aspects of the invention
described herein.

[0179] In some embodiments, the invention herein can be
construed as excluding any element or process step that does
not materially affect the basic and novel characteristics of
the dynamically tunable compositions, systems, and meth-
ods for making or using such systems. Additionally, in some
embodiments, the invention can be construed as excluding
any element or process step not specified herein.

EXAMPLES

Examples of the present invention will now be
described. The technical scope of the present
invention is not limited to the examples described
below.

Materials

[0180] Chemicals and solvents were used as received
without further purification. 2,6-lutidine (anhydrous, 99%),
2,4-lutidine (99%), 2,5-lutidine (95%), Ludox® SM (mass

Sep. 28, 2023

fraction of 30%), Ludox® TM-50 (mass fraction of 50%)
and Rhodamine B (95%) were purchased from Sigma-
Aldrich (St Louis, MO). Deuterium oxide (D, 99.9%) was
obtained from Cambridge Isotopes (Tewksbury, MA). A
different batch of 2,6-lutidine (98%) was also ordered from
‘Tokyo Chemical Industry (TCI, Portland, OR). All solvents
and chemicals were used as received without further puri-
fication.

Preparation of an Exemplary Compositions for
SeedGel Embodiments

[0181] Ludox silica particles (Ludox® TM (PH=9) and
Ludox® $M (PH~10)) are highly charged silica particles
The compositions for the SeedGel embodiment were pre-
pared by mixing silica dispersions in water with lutidine at
a specific ratio. Mixing lutidine and water does not alter the
pH value so that all silica particles remain highly charged
‘The average size of Ludox® TM and SM particles is about
27 nm and 10 nm, respectively. To form SeedGel embodi-
ment with 27 nm particles, lutidine volume of 300 pl was
added to each milliliter (ml) of Ludox® TM solution. It
corresponds to a weight fraction of 28.4% 2,6-lutidine and
71.6% water in the solvent.

[0182] Ludox® SM was used to form gel with 10 nm
particles. Lutidine volume of 200 ul was added to gel the
sample for every ml of Ludox® $M, which was equivalent
to weight fraction of 17.8%. A clear and an opaque state
were observed by eyes, but no UV-vis measurement was
conducted.

[0183] In another exemplary composition, the gelation
temperature was shifted by mixing 300 pl 2,4-lutidine or
2,5-lutidine with 1 ml of Ludox® TM solution.

[0184] Each of the above compositions were vigorously
vortexed after mixing at desired ratios, which may cause the
formation of a temporary gel at room temperature. Subse-
quent waiting time of a couple of days dissolved this
temporary gel at room temperature, which led to a homo-
geneous solution that can form thermo-reversible gel at
elevated temperatures.

[0185] It was found that a temporary gel may form due to
initial mixing, but it can be dissolved when continuous
rolling or periodically repeated vortexing is applied at room
temperature. The formation mechanism for this temporary
gel is similar to that of SeedGel embodiment in the sense
that the solvents stay separated during the initial mixing and
particles are kinetically jammed within the water-rich region
to form mechanical percolation. Note that applying rolling is
critical in the dissolution process to reach fully mixed
samples in liquid states at room temperature. In the process
of dissolving the initially formed gel, repeated vortex or
continuous low shear applied by a roller were observed to be
helpful during the first day of mixing. Additionally, the
dissolution process can be accelerated by simply cooling
down the composition to a lower temperature (4° C.) that is
well within the single-phase region of water and 2,6-luti-
dine. The compositions were used after a certain aging time.
It was found that the sample behaved the same as long as this
aging time is anywhere from one day to a few days. For
SeedGel embodiment with 10 nm particles, a waiting time of
about 20 h was used to prepare a sample after 2,6-lutidine
was mixed with Ludox® SM solution. The fully dissolved
nanoparticle dispersions can thermo-reversibly form a gel at
elevated temperatures.


US 2023/0305289 Al

that the domain size has a larger distribution than those
SeedGel embodiments at the optimal conditions.

[0142] By increasing the 2,6-lutidine ratio along the ‘opti-
mal’ condition suggested in the phase diagram in FIG. 5, the
particle volume fraction can be further reduced to 9.8%.
Similar to what is observed before, the ‘optimal’ conditions
result in periodicities of about 3 ym (Table $2-1).

TABLE S2-1

USANS fitting results of periodicity and correlation
length from Teubner-Strey model for samples prepared
with different particle concentrations and varied 2,6-
Jutidine compositions in a binary solvent system.

Particle Volume 2,6-lutidine Correlation
Fraction Weight Fraction Periodicity Length
(%) (%) (um) (um)
19.6 324 2.68 0.55
17.9 32.4 12.6 2.58
13.7 37.2 2.65 0.52
ILS 38.5 2.68 0.49
98 39.6 2.97 0.53
[0143] It should be noted from Table $22-1, that it is

possible to adjust the periodicity by changing the particle
concentration. For example, by lowering the particle con-
centration from 19.6% to 17.9%, while keeping everything
else the same, periodicity changed from 2.68 um to 12.6 um.

TABLE S2-2

Domain sizes and fractions extrapolated from the combined model
fitting. Sample A has a 2,6-lutidine mass fraction of 32.4% and
4 particle volume ratio of 16.5%. Sample B has a 2,
mass fraction of 35.7% and a particle volume ratio of.

‘The larger domain

Large domain Small domain volume fraction
Sample A 40.0 pum 2.62 um
Sample B 58.2 ym 2.99 im

Supplementary Note 2-2: Temperature Calibration
of MUZSAC Sample Environment

[0144] MUZSAC is a 6-position sample changer devel-
oped at NCNB for both SANS and USANS experiments. It
allows the independent temperature control for individual
samples with precise and rapid temperature ramping rates.
Due to the large heat capacity of the SANS cell because of
a large volume, the actual ramping rate, especially at fast
quenching, deviates from that with slow heating. In order to
calibrate the actual ramping rate inside the SANS cells at the
sample position, an additional experiment was performed to
measure the temperature change inside the SANS cell using
a temperature sensor that is placed inside the cell. The
temperature change as a function of time for four different
setting rates: 0.1° C/min, 0.5° C./min, 1° C./min, and 10°
C/min were recorded. Linear fits are used within the tem-
perature range that is of interest to determine the actual
ramping rates. For fast ramping rates, a dramatic decrease of
the ramping rates is observed when the temperature gets
close to the set temperature because of the PID loop control.
This affects the fastest setting rate of 10° C./min the most.
In order to obtain the accurate ramping rate, the region that
is close to the gelation temperature of SeedGel embodiment

Sep. 28, 2023

(around 26° C.) was used to extrapolate the actual ramping
rate for the sample. The calibrated results are summarized in
Table S2-3 below for each of the setting ramping rates.

TABLE $2-3

The averaged ramping rates and standard deviations of five calibrations
measured from the actual temperature inside the SANS cells.

Standard Deviations

Set Ramping Calibrated Ramping of Calibrated Ramping

Rates (° C/min) Rates (° C/min) Rates (° C./min)
Ol 0.0980 0.00303
05 0.483 0.0139
1 0.936 0.0319
10 1.89 0,296

Supplementary Note 2-3: Effect of Quenching
Depth on SeedGel Embodiment Formation

[0145] Different from Bijel, too large ofa quenching depth
into the spinodal decomposition region would lead to mac-
roscopic phase separation of SeedGel embodiment, as
observed in a Composition for SeedGel embodiment, where
the composition phase-separated after heating to 40° C. for
2h. A relatively clear liquid layer appeared on top, and a
cloudy, and more viscous, liquid layer stayed at the bottom.
‘The mechanical strength was reduced, and the sample could
not withstand the yield stress implemented by vial flipping,
as both liquid layers flowed to the bottom under gravity. In
comparison, as disclosed hereinabove, SeedGel embodiment
with the same composition could remain unchanged for at
least 20 h at a lower temperature of 30° C., a temperature
that is under the critical point of the bulk solvent with the
same composition.

EXPERIMENT NO. 3: TUNABLE OPTICAL.
PROPERTIES OF A THERMO-REVERSIBLE.
BICONTINUOUS NANOPARTICLE SEEDGEL

[0146] As discussed hereinabove, compositions compris-
ing nanoparticles dispersed in a binary solvent system can be
thermo-reversibly assemble into bicontinuous structures
through solvent segregation driven gel (SeedGel embodi-
ment) in a scalable, reproducible, and tunable manner. It is
interesting that dynamically tunable coloration can be real-
ized within the SeedGel embodiment framework, even with
micrometer domains. The experimental setup of scattering
mode and transmission mode are illustrated in FIGS. 6A and
6B respectively. White light can be selectively scattered
from a SeedGel embodiment of the present composition to
produce color, controlled by temperature, as shown in FIG.
6A. The SeedGel embodiment of the exemplary composi-
tion appearedd blue (short wavelength) at relatively high
temperatures and gradually transits to yellow (long wave-
length) when cooled down. Interestingly, the colored Seed-
Gel embodiment of the exemplary composition disclosed
hereinabove appeared transparent at the same time, evi-
denced by a visible back side of the sample holder. Too high
(above 29.7° C.) or too low (below 26.9° C.) of the tem-
perature increases its opacity. On the other hand, the wave-
length of transmitted light is in complement to that of
scattered light, as shown by FIG. 6A, which suggests
physical light-matter interactions. Red light (long wave-
length) is allowed to pass through the gel at high tempera-


Patent Application Publication Sep. 28, 2023 Sheet 12 of 14 US 2023/0305289 Al

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FIG. 11


US 2023/0305289 Al

METHOD TO THERMO-REVERSIBLY
CONTROL LIGHT AND HEAT FLOW WITH
BICONTINUOUS MICRO-DOMAIN

CROSS-REFERENCE TO RELATED
APPLICATION,

[0001] | This application claims priority to U.S. Provisional
Patent Application Nos. 63/056,794, filed on Jul. 27, 2020
and 63/171,139, filed on Apr. 6, 2021, the entire disclosures
of each of these applications being incorporated herein by
reference in their entireties for all purposes.

STATEMENT REGARDING FEDERALLY
SPONSORED RESEARCH

[0002] This invention was made with government support
under Cooperative Agreement Nos. 70NANB12H239 and
70NANB10H256 of the National Institute of Standards and
Technology. The government has certain rights in the inven-
tion.

BACKGROUND OF THE INVENTION

[0003] Colloidal self-assembly can form fascinating struc-
tures through either equilibrium or non-equilibrium routes.
Gel formation, a non-equilibrium approach, shows tremen-
dous usefulness to form novel structures not achievable with
traditional equilibrium approach. In particular, the formation
of bicontinuous structures through gelation processes has
attracted extensive research interests due to their applica
tions in energy storage, membrane science, flow-through
reaction, and cell delivery. One of the widely studied bicon-
tinuous structure systems is the bicontinuous interfacially
jammed emulsion gel (Bijel), which can form porous mate-
rials with tortuous channels by arresting the solvent spinodal
decomposition with colloidal particles trapped at the inter-
face of two phase-separating solvents. However, as non-
equilibrium structures are process-dependent, it is very
challenging to simultaneously achieve reversibility, repro-
ducibility, scalability, and tunability over material structures
and properties. For example, for Bijel systems, the required
fast quenching rate (from a few to tens of degrees per
minute) has been restricting its scalability and thermal
reproducibility. Extensive works have been focused on sim-
plifying the experimental requirements of Bijel systems,
improving their large-scale processability, boosting the ver-
satility and enhancing the control over domain size.
[0004] Furthermore, various photonic devices have been
developed during the recent years, including smart windows,
optical switches/filters, displays, and memories, all of which
harness light-matter interactions. Their physical interference
could result in coloration through absorption, transmission
and scattering. Light absorption (e.g. pigment) is commonly
used to select or filter out certain wavelength of light.
However, it often involves toxic material and suffers from
photo-degradation. In addition, heat generated through
absorption is also detrimental to thermal management.
[0005] Structural color, resulting from light scattering, is
one of the major components that form the color palettes of
nature, such as bird feathers, beetle scales, flower petals and
plant fruits. By mimicking nature, man-made structural
color can be originated from photonic crystalline structures
(PCSs) and photonic amorphous structures (PASs). Com-
pared to PCSs, PASs lack of long-range order and exhibit
less angle-dependent colors (non-iridescence). Typically, the

Sep. 28, 2023

length scale of short-range order is defined by the size of
solid building blocks (i. particles). They are usually par-
ticles of a few hundred nanometers similar to the wavelength
of visible light. By changing the size of the particles, the
specific wavelength of light that interacts with the structure
is altered, thus the sample could exhibit different colors. As
PASs show angle-independent structural color, great efforts
have been made to create real “amorphous” structure to
suppress Bragg scattering. Intentional incorporation of par-
ticles with different sizes, fast infiltration, evaporation, intro-
ducing opposite charged layers, and growth of soft shells are
all utilized to disrupt long-range order. Recently, Goodling,
A. E. et al. (Nature 566, 523-527 (2019) proposed a new
mechanism to produce iridescent colors through total inter-
nal reflection with macroemulsions. Still, it is relatively rare
to achieve structural color with micro-domains.

[0006] Controlling light transmission, on the other hand,
leads to important applications, such as smart windows,
optical filters and displays. Traditional smart window and
optical filter technologies largely depend on light absorption
of materials. Recent developments, however, start to favor
structural color filtration. As such, scattering based smart
windows/coatings, as well as Fabry-Pperot nanocavities,
liquid crystal filters, semiconductor fibers plasmonic and
metamaterial filters are developed. Similar to structural
color, effective management of visible light transmission
often requires structure size or periodicity to be similar to the
wavelength of visible light.

[0007] There are intrinsic limitations associated with the
current techniques, such as high fabrication cost involving
multi-step of lithography, lack of control over the wave-
length of light (color clarity), as well as the difficulty in
achieving dynamic tunability. For structural scattering and
transmission, the most widely used way to realize in-situ
light management is by introducing stimuli-responsive mac-
romolecules to dynamically change certain repeating dis-
tances. As a result, the unique response of polymers to
stretching, temperature, moisture/UV, and PH can be
directly translated to color change. However, alternative
approach to realize dynamical tunability have not been
reported before.

[0008] Hence, there is a need to develop a new mechanism
to thermo-reversibly manage light transmission and scatter-
ing and a general method to achieve dynamical optical
modulation and allows customization on the transition tem-
perature.

SUMMARY OF THE INVENTION

[0009] Disclosed herein is a colloidal composition that can
form bicontinuous structures in a gel state, referred to herein
as a solvent segregation driven gel (SeedGel embodi-
mentTM). Similar to Bijel, colloidal particles dispersed in a
binary solvent are used in the compositions for the SeedGel
embodiments of the present disclosure. However, unlike
Bijel systems as shown in FIG. 1A, particles in a SeedGel
embodiment, as illustrated in FIG. 1B, are jammed within
one solvent domain due to preferential wetting of particles
by one component of the binary solvent upon solvent phase
separation. It should be noted that realizing bicontinuous
structures with particles constraint within one of the liquid
domains has been previously proposed in polymer blends
and bicontinuous intraphase jammed emulsion gels (bipjel)..
However, there are major distinctions between SeedGel
embodiments of the present disclosure and the previous