**Notes from CINT Workshop #3: Self-Assembly Discovery Platform™
Breakout Session.**

Opening remarks by Jun Liu: For synthesis, the issue is to follow in
real time batch reactions. They suffer from variations in batches,
changing chemical environments, no feedback mechanisms, and are
difficult to scale up. What is needed are cheap, scalable production
routes to nanomaterials. For self-assembly, it is difficult to scale up,
and another question is how to integrate synthesized materials into a
real device. An example was used of molecular beam epitaxy, which has
multiple sources, external control and the potential for in situ
feedback mechanisms in material formation. It is a very sophisiticated,
reproducable, and highly integrated tool. The scientific concept that
Discover Platforms should realize is science based, predictive, robust,
and scalable.

Paul Braun gave his talk on coupling self-assembly with complexity,
using the example of the formation of photonic crystals. Methods include
colloidal approaches (sedimentation, convective evaporation, and forced
filtration) as well as optical techniques using holography. Much
discussion was provided on the function of confocal force microscopy for
observing colloidal systems in situ during formation, and for two-photon
writing in photo-resists to create unique structures around opal film
templates. Regarding optics in Discovery Platforms™, they are compatible
with fluid systems, offer multiple beams, local monitoring of 3D
structure, and potentially AFM over the confocal. The technique needs
better spatial resolution, contrast, nominally transparent materials,
and a complex platform for execution. The depth of focus is key in
design of the substrate.

Yunfeng Lu spoke about efficient routes to nanomaterials and
nanodevices. Self-assembly defined as spontaneous organization by
non-covalent interactions. Templates include organic molecules like
dendrimers, polymer, polyelectrolytes, and biomolecules. Inorganic
nanoparticles used as building blocks, and there is a great need to link
them using biomolecules, control of surface charge, and tuned
interactions. Other forces driving control of self-assembly include
magnetic fields, capillary forces, confined features, electric field,
and patterning of preformed nano-systems. Templated assisted
self-assembly can utilize patterning of surfaces or lithography.
External field assisted SA includes flow field or electric field, and
Langmuir-Blodgett techniques. There is a large library of building
blocks, but it is difficult to combine the building blocks. Direct
synthesis of nano-systems formed by CVD, seeded solution growth,
surfactant templated growth (of films) which allows for control of
precursors and 3D structural control. Responsive nanosystems are formed
using dynamic assembly. The driving force for a self-assembling system
is a negative enthalpy for the system, provided by hydrogen-bonding or
other non-covalent interactions like π- π stacking. An example was
provided using amphiphilic diacetylene binding molecules in polymers
under stress. This gives thermal control of optical properties. In a
microsystem, you could control optical filtering properties or use it as
a sensor.

There are three approaches to assembly

1.  Assembly of building blocks

2.  Direct synthetic approaches

3.  Dynamic nanosystems

H.R. Tseng from UCLA Dept. of Medicine spoke for \~10 minutes on the use
of microfluidic networks as micro-reactors to synthesize special
molecules used in cancer detection and imaging in the body. Tools used
included a nanoelectronic sensor (conductive polymer nanowire connecting
two electrode junctions. Compound synthesis was followed on a microchip
platform, and optimized. By using microfluidics, the conversion
efficiency of this unstable molecule was 98.99%, and much less material
was necessary to synthesize for treatment of the patient. It was a very
impressive demonstration of the benefits of micro-reactors for synthesis
procedures. Their components incorporated microfluidic networks,
valving, heating stages and circulatory control.

**Accomplishments**

Study of synthesis and scale up operations of self-assembly were divided
into three classes of study:

1.  Assembly of building blocks

2.  Direct synthetic approaches

3.  Dynamic nanosystems

Scale up methods for mass production/application are still unknown.

**Decisions**

Platforms should be standardized for systems of particles, surfaces, and
molecules. Additional capabilities necessary for a specific user can be
created by the development of modular sensors. In practice, the CINT
staff will click together components to build a desired microfluidic
instrument

It will be necessary in the ramp up time for CINT operations to develop
these capabilities both in MEMS at SNL as well as with users who are
experts in microfluidics and in sensor or instrument technologies.