2024 7th International Conference on Soft Robotics (RoboSoft)San Diego, CA, USA. April 14-17, 2024

Liquid crystal elastomer and fabric bilayer actuators

2024 IEEE 7th International Conference on Soft Robotics (RoboSoft) | 979-8-3503-8181-8/24/$31.00 ©2024 IEEE | DOI: 10.1109/ROBOSOFT60065.2024.10521999

Sophia Eristoff1 , Lily Behnke1 , Lina Sanchez-Botero1,† , Sree Kalyan Patiballa1,‡ ,and Rebecca Kramer-Bottiglio1

A

Abstract— Liquid crystal elastomers (LCEs) are a promisingclass of responsive materials for shape-morphable structuresdue to their large deformation, tunable properties, and low
power consumption. It is well-known that by laminating acontracting LCE with an inert but flexible material layer,bending actuation can be achieved. We report a method tofabricate thermoresponsive LCE and fabric bilayer actuatorsand characterize their utility as bending actuators. We findthat the use of different strain-limiting fabrics yields varying
actuation outputs and curvatures, which we discover to bereliant on the interfacial adhesion of the bilayer, rather than
the stiffness of the strain-limiting layer. We demonstrate theefficacy of the proposed LCE-fabric bending actuator in a soft
robotic gripper. The findings herein can be applied to the designof LCE and fabric bilayer structure patterns to realize complex
and programmable out-of-plane morphing.

Cool

B

LCE
Anisotropic
Configuration

5 mm

LCE
Isotropic
Configuration

Heat
Cool

FabricLCE Contraction
Shape memory effectC

I. INTRODUCTION

Bending

Same fabric, same stiffness
Heat

Biological systems achieve controllable shape morphing in
response to environmental cues that allow them to function
safely and robustly in diverse environments. For example,
pine cones open and close passively in response to ambient
humidity [1], bauhinia seed pods transform from a flat sheet
to a helix in response to humidity [2], and wheat awns willreversibly bend in response to their environment to propel
seeds onto the ground [3]. The controlled shape morphingin these plants is due to the underlying bilayer mechanism
and is critical to their growth patterns and sustenance. The
bilayer mechanism is a bioinspired phenomenon of differential growth-driven morphogenesis in plants and biologicaltissues, wherein nonuniform growth amongst thin elastic
membranes leads to out-of-plane deformations [4].
Shape morphing has been one of the primary goals in
extending the vast capabilities of bioinspired soft robots [5],[6]. While systems-based actuators, such as pneumatic or
hydraulic actuators, are vast and useful, stimuli-responsive
materials can be used to emulate the desired bio-inspired
shape-changing behavior in soft robots. Environmental cues,
such as a change in temperature, humidity, or magnetic field,
can warrant a response from materials that effectively pro-

Heat

10 mm

High interfacial adhesion

10 mm

Low interfacial adhesion

Fig. 1. A) Reversible actuation of a liquid crystal elastomer (LCE). A
programmed aligned LCE (left) will contract when heated (right), and return
to its initial programmed shape when cooled. B) Schematic of LCE-fabricbilayer actuators. C) Images of bilayer actuators, with high/low interfacialadhesion, undergoing curvature when subject to thermal stimuli.

vides the desired shape change. Furthermore, when stimuliresponsive materials are used in a bilayer configuration,
actuation similar to natural systems can be achieved [7], [8].
In this work, we chose liquid crystal elastomers (LCEs)
because of their reversible actuation and large deformation
range [9], [10]. LCEs are materials that combine the longrange orientational order of liquid crystals with the entropic
elasticity of traditional elastomer materials. The combination of the two counteracting properties of LCEs, ordered
and disordered, results in a unique shape-memory behavior
when exposed to various environmental cues. Thermotropic
liquid crystals respond to a change in temperature, whichhas proven helpful in several applications where remote
operation or tunable stimulus response is desirable [11], [12].
As a result, LCEs are an emerging technology within thesoft robotic realm, attributed to their substantial thermallyinduced reversible shape change [10], [13].
LCEs can be programmed to hold a specific shape below their clearing temperature (Tc ; nematic state) and aseparate shape past their Tc (isotropic state) (Figure 1A).
Because LCEs are generally planar contracting actuators,
it can be challenging to accomplish complex out-of-plane
shape morphing. In previous works, out-of-plane LCE de-1 Department of Mechanical Engineering & Materials Science, Yale
University, 9 Hillhouse Avenue, New Haven, CT 06520, USA. (email:rebecca.kramer@yale.edu)† L.S-B. is currently affiliated with: Department of Radiology, Weill
Cornell Medicine, New York, NY 10021, USA,
‡ S.K.P. is currently affiliated with: Department of Mechanical Engineering, University of Alabama, Tuscaloosa, AL 35487, USA.
S.E. was supported by a NASA Space Technology Graduate Research
Fellowship (80NSSC21K1269). L.B. was supported by a National Science
Foundation (NSF) Graduate Research Fellowship (DGE-2139841). L.S-B.
was supported by the NSF under grant no. IIS-1954591. S.P. was supportedby the Office of Naval Research under grant no. N00014-21-1-2417.

979-8-3503-8181-8/24/$31.00 ©2024 IEEE

Heat

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B

C

D

CourseA

500 μmF

Stress (MPa)

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G 25
Cotton Course
Cotton Wale
Nylon Course
Nylon Wale
Muslin10 1

500 μm

H
Cotton Course
Cotton Wale
Nylon Course
Nylon Wale
Muslin20

Stress (MPa)

Cotton Course
Cotton Wale
Nylon Course
Nylon Wale
MuslinFlexural Stress (MPa) @ RT

E 25

500 μmFlexural Stress (MPa) @ 80°C

Wale

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Cotton Wale
Nylon Course
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Muslin

10 1

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80

100

Sample Type

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Strain (%)

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Sample Type

Fig. 2. A) Schematic of a knitted structure, indicating its respective components. B-D) Scanning electron microscopy (SEM) image of fabric samples of(B) cotton, (C) nylon, and (D) muslin. The colored axis represents the course and wale of relevant fabrics. E) Stress-strain measurements taken at room
temperature of individual fabrics. Inset is a zoom-in of cotton and nylon samples. F) Flexural stress measurements taken at room temperature of fabricsamples at 15% strain (y-axis is on a logarithmic scale). G) Stress-strain measurements taken at 80 °C of individual fabrics. Inset is a zoom-in of cottonand nylon samples. H) Flexural stress measurements taken at 80 °C of fabric samples at 15% strain (y-axis is on a logarithmic scale).

of toluene and heated at 80 °C until the material became ahomogeneous liquid. Thereafter, 0.217 g of pentaerythritol
tetrakis(3-mercaptopropionate) (PETMP) and 0.9157 g of2,2’-(Ethylenedioxy)diethanethiol (EDDET) were added tothe solution to yield a ratio of 15:85 PETMP:EDDET.
Finally, 0.0257 g (2-hydroxyethoxy)-2-methylpropiophenone(HHMP) photoinitiator and 0.568 g of diluted dipropylamine(DPA) catalyst (1:50 DPA:Toluene) were added to the solution and mixed vigorously using a Vortex mixer. The solution
was poured into an acrylic mold, degassed in a vacuum toremove any bubbles, and allowed to cure overnight at room
temperature. After curing, the sample was removed from themold and placed in an oven at 80 °C overnight to remove
any remaining toluene.
Programming of the anisotropic nematic state wasachieved by exposing the sample to a UV light set to 365 nm
wavelength for 30 min. Past the clearing temperature (Tc ),the structure will hold its isotropic as-cast state and below
the Tc , the structure will hold its anisotropic nematic state.
b) Strain-Limiting Layer: Incorporating strain-limiting
layers into the liquid crystal elastomer involves adhering precut and un-stretched fabric pieces onto the LCE matrix usingslightly gelled LCE. The knitted fabrics, nylon and cotton,
appear to have a different front and back structure. The sideof the fabric with the larger and more distinguishable topological features was chosen and consistently used throughout
this study. The slightly gelled LCE was synthesized using thesame chemical formula described above but was cured forapproximately one minute so that the viscosity increased,enabling easier manipulation of the material to allow for
attachment of the pre-cut fabric to the cured LCE samples.
After that, the materials were allowed to cure under compression to yield SLiCE composites (Figure 3A).

formation has been achieved with a bilayer mechanism [14],[15], but requires complex synthesis techniques for optimal interfacial adhesion. Furthermore, stretching of LCEs
prior to programming has been shown to impart curvatures
throughout the structure [16], [17]. Finally, modulating LCE
nematic director orientations pixel-by-pixel can produce outof-plane motion, but is time-consuming and requires solving
a computationally expensive inverse design problem [18],[19], [20].
In this paper, we propose a facile fabrication procedure
for shape-morphable liquid crystal elastomeric composites(SLiCEs), which are material systems that leverage thebilayer mechanism by adhering thermoresponsive LCEs tofabric strain limiters to achieve complex out-of-plane deformations (Figure 1B, Supplementary Video). We first survey
and characterize several different fabrics to be used as
effective strain-limiters. Thereafter, we synthesize SLiCEs
and characterize their mechanical properties and actuation
properties. We find that the actuation performance of theSLiCEs is dominated by the interfacial adhesion between
the LCE and fabric (Figure 1C), rather than the stiffness
differential between the layers. Finally, we show how thecomposite can be used effectively for robotic applications.
With this study, we hope to provide a deeper understandingof the mechanics behind bilayer soft actuators using thermoresponsive LCEs.
II. M ATERIALS AND M ETHODSa) Synthesis of LCE: Liquid crystal elastomer (LCE)with mesogen RM 257 was synthesized using previously described techniques [9], [21]. First, 4 g of themesogen 1,4-Bis-[4-(3-acryloyloxypropyloxy)benzoyloxy]2-methylbenzene (RM 257) was added to a vial with 1.6 g
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UV cureprogramming

A

B

Degas LCE-fabriccomposite

FabricCast in moldand cure
Heat

D

4

1

0

20

40
60
Strain (%)

80

100

15

L-Cotton Course
L-Cotton Wale
L-Nylon Course
L-Nylon Wale
L-Muslin
LCE

10

F

1.5

Stress (MPa)Stress (MPa)2Flexural Stress (MPa) @ RT

L-Cotton Course
L-Cotton Wale
L-Nylon Course
L-Nylon Wale
L-Muslin
LCE

500 μm

E

20

3

0

LCE strained
to induce anistropy

FabricAttach fabric withpre-cure LCE

20
L-Cotton Course
L-Cotton Wale
L-Nylon Course
L-Nylon Wale
L-Muslin
LCE

1

Flexural Stress (MPa) @ 80°C

Liquid crystal
elastomer

C

LCE

LCE

0.5

5

0

0

Sample Type

0

20

40
60
Strain (%)

80

100

15

L-Cotton Course
L-Cotton Wale
L-Nylon Course
L-Nylon Wale
L-Muslin
LCE

10

5

0

Sample Type

Fig. 3. A) Schematic of the synthesis method of SLiCE bilayer actuators. B) Cross-sectional optical microscopy image of a SLiCE actuator. C-F) For all
SLiCE actuators and neat LCE: (C) Stress-strain measurements taken at room temperature, (D) Flexural stress measurements taken at room temperature at
50% strain. (E) Stress-strain measurements taken at 80 °C. (F) Flexural stress measurements taken at 80 °C at 50% strain.

c) Physical and Mechanical Characterization: Scanning electron microscopy (SEM) images were obtained using
a Hitachi Su-70 at 2 kV. All samples were coated withiridium (nominally 8 nm) before SEM imaging. Crosssectional optical microscopy images were taken with a Zeiss
Smartzoom 5. Curvature measurements were filmed andpost-processed using Python OpenCV image packages.
All stress-strain and 3-point bend measurements were
performed using a dynamic mechanical analyzer (DMA
Q850, TA Instruments). The stress-strain and 3-point bend
measurements were both taken at a rate of 30 mm/min. Actuation stress and T-peel measurements were performed using amaterials testing system (Instron 3345). T-peel measurements
were taken at 30 mm/sec. All neat fabric samples were tested
without any pre-stretching. At least five samples were tested
for each mechanical characterization.

and appears to be isotropic in the parallel and perpendicular
directions, no directionality is indicated or differentiated.
All knitted fabrics were mechanically characterized in either
the course or wale direction (for a ‘course’ sample, thecourse of the fabric would be parallel to the tensile strain
and perpendicular to the bending strain), and muslin ischaracterized in the direction parallel to the thread.
Figure 2E shows stress-strain measurements taken at room
temperature for all the fabrics. Due to the high stiffnessof muslin, the sample could not be strained past 25%. Allof the other samples exhibit similar mechanical properties
in the tensile configuration. The inset shows that in thecourse and wale direction, nylon typically exhibits similar
properties, but there appears to be larger differences in tensile
properties between cotton in the course and wale direction.
Flexural stress measurements at 15% strain of the fabrics
taken at room temperature show muslin having the highest
flexural stress, approximately an order of magnitude higher
than any of the other samples. Nylon course has a notably
higher flexural stress when compared to nylon wale andcotton wale, which have similar flexural stress measurements.
Cotton course does exhibit the lowest flexural stress and istherefore the least stiff in a bending configuration.
Because the fabrics will be subject to high temperatures
when integrated with the LCE to enable actuation, thefabrics are tested at the Tc of LCE (80 °C). Figure 2G
shows the stress-strain properties of the fabrics at the Tc .
The results do not differ much from the room temperature
results, where muslin is significantly stiffer than all theother fabrics. Similarly, flexural stress measurements taken
at 15% strain at the Tc show that muslin has the highest

III. FABRIC C HARACTERIZATION
Fabrics were chosen as effective strain-limiting layers topair with LCE actuators due to our early observations of
pre-cure LCE wetting, spreading, and wicking on candidate
fabric substrates. Typically, fabrics are knitted or woven ina specific manner in which the fabric may have a lengthwise or cross-wise grain. Figure 2A shows the directionalitythat may arise from knitted fabrics, which are composed ofcourses and wales. Figures 2B-D show scanning electron
microscopy (SEM) images of the three different fabrics
chosen, which are jersey cotton (knitted), nylon (knitted), andmuslin cotton (woven), respectively. For the knitted patterns,
jersey cotton and nylon, course and wale are indicated on
the SEM images. Because muslin is a plain-weave fabric
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B 400Upper plate
lowered to establish
contact with sample

Heat
Heat

D
L-Cotton Course
L-Cotton Wale
L-Nylon Course
L-Nylon Wale
L-Muslin

Actuation Stress (kPa)Sample bends
towards upper
plate

300

200

100

0

E

C
L-Cotton Course
L-Cotton Wale
L-Nylon Course
L-Nylon Wale
L-Muslin
LCE

L-Cotton Course
L-Nylon Course

L-Cotton Wale
L-Nylon Wale
L-Muslin

1.5

1

0.5

0

Sample TypeF

Sample TypeG
L-Nylon Wale

L-Cotton Course

2
Peel Stress (MPa)AA

L-Muslint = 60st = 60st = 50st = 60st = 30st = 0s5 mm

t = 50st = 30st = 50st = 30st = 0st = 0s5 mm

5 mm

Fig. 4. A) Schematic of method to measure actuation stress of SLiCE actuators using a universal testing system. B) Actuation stress measurements ofall SLiCE actuators, with neat LCE as a control. C) T-peel stress measurements of SLiCE actuators. D) Curvature measurements for each SLiCE actuatoraveraged over three samples. E-G) Overlaid curvature sequences of (E) cotton course composite actuator, (F) nylon wale composite actuator, and (G) muslin
composite actuator over 60 seconds.

flexural stress, followed by nylon course. Nylon wale andcotton wale have similar flexural stress measurements, andcotton course exhibits the lowest flexural stiffness. Flexuralstress measurements show slight variations with temperaturechange, unlike stress-strain measurements, which may be dueto the higher strains reached in the bending configuration,corresponding to significantly higher stresses measured.

distinguish composite actuators from neat fabric. Figure 3B
shows a cross-sectional optical microscopy image of a SLiCE
actuator.
The SLiCE actuators, which comprise both LCE andfabric, exhibit different mechanical properties compared to
the neat fabrics or the neat LCE. Figure 3C shows stressstrain measurements taken at room temperature of all SLiCE
composites and neat LCE. The muslin composite exhibits thehighest stiffness, followed by all the other composites, with
the neat LCE exhibiting the lowest stiffness values. Flexuralstress measurements at 50% strain of the composites taken atroom temperature show that the muslin composite exhibits
the highest flexural stress, followed by neat LCE, and theother composites are all approximately within the same rangeof flexural stress values (Figure 3D).

IV. C OMPOSITE S YNTHESIS AND C HARACTERIZATION
SLiCE actuators are synthesized using the methods shownin Figure 3A. First, an LCE sample is synthesized and cured.
An LCE structure can be programmed to have its mesogens
in an anisotropic configuration by straining the sample under
UV light. When heated past a Tc (approximately 80 °C),
the LCE structure returns to its isotropic configuration bycontraction. The contraction of the LCE is due to themesogens no longer holding topological restrictions on thepolymer matrix. Thereafter, the fabric is laminated to the
LCE via the addition of pre-cure LCE, when the LCE isin its extended state. Post-cure, the composite is degassed,
yielding a bilayered SLiCE actuator.
Due to the different directionalities of the fabric, for bothcotton jersey and nylon, the fabric is attached with the waleor course pattern going along the axis of actuation on the
LCE. If the wale or course is parallel to the axis of actuation,
the sample is denoted as ‘wale’ or ‘course’, respectively. For
the muslin samples, the fabric is attached with the threadboth perpendicular and parallel to the direction of the axisof actuation. We label the composite actuators using justthe fabric and directionality for simplicity, but add ‘L-’ toWhen the composites are heated past the Tc of LCE,
80 °C, different trends arise in both the tensile and bending
configurations. As the LCE is heated past its Tc , the LCE
undergoes an anisotropic to isotropic phase-change, which
reduces the overall stiffness of the LCE. The reduction
in stiffness of the LCE has a noticeable effect on the
SLiCE actuators, where all samples exhibited a decreasein stiffness when compared to the samples measured atroom temperature (Figure 3E). However, while the muslin
composite remains the stiffest at Tc , the nylon composite
samples and cotton composite samples diverged from eachother, showing clear distinctions in responses to tensile strain
at the Tc . Flexural stress measurements at 50% strain of thecomposites taken at the Tc show a decrease in flexural stressfor all samples except the muslin composite (Figure 3F). A
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Heat

Grip

Retract

Cool
Release10 mm

Fig. 5.

Robotic gripper comprised of SLiCE actuators can grip objects when hot and release objects when cooled.

more substantial drop in flexural stress of the cotton walecomposite is noted (45% reduction in flexural stress) whencompared to that of the other cotton and nylon composites(approximately 20-30% reduction in flexural stress).

cotton course composites exhibiting the highest curvature—
the differences are less drastic. Figures 4E-G show overlaid
curvature sequence images over 60 seconds of cotton course,
nylon wale, and muslin composites respectively. The cotton
course composite achieved significantly higher curvatures inthe same time frame as the other two samples, with thenylon wale composite showing drastically lower achieved
curvatures than the muslin and cotton course composites.
To showcase relevant demonstrations of the SLiCE actuator in the context of soft robotics, we rationally implement
strain-limiting layers onto LCE to yield a three-finger robotic
gripper (Figure 5). As the composite material will curl
towards the direction of the contracting LCE and away fromthe fabric, we oriented the fabric layers to face outwards ofthe gripper. The LCE contracts when subject to heat, but
the fabric layer acts as a strain-limiting layer, causing eachbilayer to undergo a curling motion. Thereon, the gripper cangrasp and lift off a petri dish lid. Once cooled, the contracted
LCE layer returns to its original shape, allowing the gripper
to release the item (Supplementary Video).

V. C OMPOSITE ACTUATION AND D EMONSTRATION
Due to the application of strain-limiting fabric to the
LCE sample, rather than undergoing axial contraction andexpansion, the actuator produces a force out-of-plane. This
force can be characterized by methods shown in Figure 4A
and adapted from Buckner et al [22], where the blocked
bending tip force in response to heat is measured in acompression configuration on a universal testing system.
The results of this characterization are shown in Figure 4B,
where neat LCE with no strain-limiting layer is measured
as a control sample. The cotton course composite exhibits
the highest actuation stress value by far, with cotton wale,nylon course, and muslin composites all exhibiting approximately the same actuation stress values. Finally, thenylon wale composite exhibits the lowest actuation stressvalue. Interestingly, the mechanical characterizations of thecomposites shown in Figure 3 indicate that other than themuslin composite, the other composites all exhibit similartensile and bending mechanical properties. However, despite
having similar mechanical properties, other than muslin, theactuation properties are vastly different.
T-peel tests were conducted to determine the interfacialadhesion between the LCE and fabrics. Figure 4C showsthat the measured interfacial adhesion appears to be highest
for the cotton course composite, lowest for the nylon walecomposite, and similar for all the remaining composites.
Notably, the trends found in the T-peel measurements appear
to match the trends found in the actuation stress measurements, indicating that interfacial adhesion (rather thanstiffness differential) may be the dominant variable that ispredictive of the actuation stress properties of LCE-fabricbilayer actuators.
Finally, the curvature of the SLiCE actuators was characterized and measured to determine if the trends with actuation stress and interfacial adhesion translated to curvature.
Figure 4D shows normalized curvature with respect to time,with each line representing the average of three separate
samples. While the curvature trends do follow those observed
for actuation stress—with nylon wale composites exhibiting
the lowest curvature, cotton wale, nylon course, and muslin
composites exhibiting similar curvature paths, and finally the

VI. D ISCUSSION AND C ONCLUSION
In this work, we reported a simple method to laminate
thermoresponsive LCE with strain-limiting fabrics to create
bilayer bending actuators. The actuators, which we call
SLiCE actuators, are granted actuation stress and out-ofplane curvatures. We surveyed several fabrics with different
physical and mechanical properties to determine which fabricyields the most optimal actuator. In doing so, we found thatthe actuation stress and blocked curvature force of the bilayer
actuators correspond to the interfacial adhesion between
layers, as opposed to the stiffness differential between the
two layers.
We elucidated how we can increase the actuation stressof bilayer actuators, which are frequently used in the fieldof soft robotics to enable desirable motions. For example,
one might assume that because the bilayer mechanism isdriven by a strain-limiting layer that prevents the actuatorfrom contracting/extending along the plane, using the stiffest
strain-limiting layer may optimize the actuation stress. However, we found that the stiffest material, muslin, does notyield the highest actuation stress. Instead, we found thatthe fabric that had the highest peel stress when laminatedto the LCE gave the highest actuation stress, indicating
the interfacial adhesion between the LCE and the fabric is563

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the most dominant variable that is predictive of actuation
performance.
A large body of literature covering bilayer actuators indeed
emphasizes interfacial adhesion. However, the motivation
typically does not involve enhancing actuation stress, butrather attaching two materials that are difficult to bond together and preventing material delamination. In this study, we
hope to bring attention to the important factor of interfacialadhesion, and further motivate the enhancement of interfacialadhesion between materials to optimize bilayer actuators andtheir actuation capabilities.
We also discovered that knitted fabrics, nylon and cotton
jersey, exhibit vastly different mechanical properties whenoriented in different directions, and can have varying mechanical properties at different temperatures. The orientationof the knit pattern is also very important when adhering
to other substrates, as we found that when LCE is adhered
parallel to the course of the fabric, the interfacial adhesion
is substantially higher than when parallel to the wale ofthe fabric. We hypothesize the differences in adhesion may
be in part due to contact splitting mechanics [23], [24].
That is, when peeling or shearing parallel to the course, thefabric presents distinct sub-contacts that would inhibit crack
propagation and enhance shear adhesion. However, factors
such as fiber content, knit structure, fiber morphology, andtechnical side adhered may also play a role in the adhesion
between the fabric and the LCE. Future work will further
investigate the interfacial adhesion between the fabrics and
LCE, as well as the generality of our finding that bilayer
actuation is more reliant on interfacial adhesion than the
stiffness differential between the layers.
By using a simple method to achieve out-of-plane shapechange in thermoresponsive LCEs via the addition of astrain-limiting fabric layer, and elucidating the mechanism toenhance this actuation behavior, we have contributed to thecurrent landscape and understanding of soft bilayer actuation.

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A PPENDIX
1,4-Bis-[4-(3-acryloyloxypropyloxy)benzoyloxy]-2methylbenzene (RM 257) was purchased fromWilshire
Technologies(Princeton,
NJ).
Toluene,Pentaerythritol tetrakis(3-mercaptopropionate) (PETMP),
2,2’-(Ethylenedioxy)diethanethiol (EDDET), Dipropylamine(DPA), and (2-hydroxyethoxy)-2-methylpropiophenone(HHMP) were purchased from Sigma Aldrich (St. Louis,
MO). Nylon 4-way stretch fabric was purchased from
Amazon (Rex Fabrics). Cotton jersey fabric was purchasedfrom Amazon (Robert Kaufman). Cotton muslin fabric waspurchased from Amazon.
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