Page 69 - ASME_NEMB_2016_Program

TRACK 5 TRACK 5 Technical Program

is no reliable and practical approach available for scalable manufacturing of processes with sophisticated skills and instrument. In nature, on the contrary,
multicomponent and multifunctional NPs to industrially relevant level (~kg/h biological systems have created delicate and refined 3D nanostrucrtures for
or even higher as needed). This is not only because the underlying mech- a long time. Due to their unique optical/mechanical properties and geome-
anism of flow-induced NP assembly in current microfluidic methodology try, not to mention their abundance and excellent biocompatibility, biological
remains elusive, but also current early-stage microfluidic approaches have nanomaterials have inspired researchers to directly utilize or replicate them
relied on conventional syringe pumps, which are not robust methodology for micro/nanoelectromechanical systems (MEMS/NEMS).
for scalable manufacturing of NPs due to several problems including the
limited syringe size and the open-loop control-based operation unable to In this work, we report an innovative type of rotary micromotors assem-
compensate for unexpected disturbances in the manufacturing process re- bled from biological 3D micro/nanostructures for microfluidic applications.
sulting in non-robust production operations. Here, we present a new large- The micromotors are comprised of diatom frustules, patterned magnetic
scale integration (LSI) of parallelized microfluidic reactors with high-precision microdisks, and quadruple microelectrodes working as rotors, bearings,
microfluidic pressure control system, which allows for mass production of and stators, respectively. Diatoms are unicellular photosynthetic algae liv-
multicomponent therapeutic NPs. In this study, we use our LSI microfluidics ing in marine ecosystems. They create silica cell walls called frustules with
technology to demonstrate a representative example of scale-up synthesis ordered micro/nanoscale pores on the surface in different geometries and
of lipid-PLGA NP (LPNP) in a parallelized microfluidic array (PMA). Each single dimensions resembling photonic crystals. The frustule rotors were prepared
microfluidic reactor in the PMA operates at a Reynolds number of 250 to through a simple cleaning and filtration process of diatomaceous earth pow-
create optimal microvortex flow patterns to strongly mix an organic solution ders followed by deposition of a thin film of Cr/Ni/Au. These metal-coated
of poly(D,L-lactide-co-glycolide)(lactide:glycolide (50:50)) (PLGA) in acetoni- frustules can be readily manipulated by the electric tweezers based on
trile with an aqueous solution of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine combined DC and AC electric fields with a maximum speed of ~140 µm/s
(DPPC) and 1,2-Distearoylsn- glycero-3-phosphoethanolamine-N-[me- and assembled onto prepatterned micromagnets into working rotary micro-
thoxy(polyethylene glycol)-2000] (PEG2000-DSPE) in a 3:7 molar ratio motors. The micromotors can rotate both clockwise and counterclockwise to
in 4wt% ethanol. We evaluate the size uniformity of produced NPs using a maximum speed of ~2800 rpm, controlled by the frequency and intensity
dynamic light scattering (DLS) and transmission electron microscopy (TEM). of the electric fields. Multiple frustule motors can be assembled and actu-
Computational fluid dynamics (CFD) simulations allowed optimization of a ated in ordered arrays with fully controlled rotation speed and orientation.
single microfluidic reactor dimensions (a cylinder of diameter of 2mm and With understanding of the frequency-dependent rotation behaviors, for the
height of 5mm) and the operating flow rate condition (Reynolds number of first time, we realized individually controllable rotary micro/nanomotors,
250). The PMA model has 25 single microfluidic reactors parallelized into which are highly essential for many applications including nanorobotics and
a 5x5 array system. This array system was designed and optimized using nanomachineries. Finally, the micromotors were successfully assembled
an electrical circuit model and CFD simulations to operate at the same and actuated in microfluidic channels as micromixers and micropumps. The
condition for each reactor while minimizing pressure difference among 25 innovations reported in this work could provide a cost-effective and facile
single microfluidic reactor inlets. We utilized one simplified electrical circuit approach for the fabrication of sophisticated micromachines with functional
model to optimize the ratio of the impedances between the flow path of three-dimensional nanostructures, and they are relevant to microfluidics,
the array network to have as same flow rates as possible at each reactor MEMS, biosensing, and lab-on-a-chip architectures.
inlets in the PMA system. The developed PMA model that allows for a pro-
duction rate of 315g/h, which is approximately 1000 times higher than that
of our previous approaches. Our custom high-precision control system was
developed by modeling a fluidic circuit using two variable resistances con-
trolled by linear actuator displacements, with control over the input of a high
pressure source and a low pressure outlet. The system was tuned using a
proportional-integrative-derivative (PID) controller to achieve fast response
less than 0.3 s settling time, and long term stability, error less than 0.5%.
The pressure range of the control system is sufficient for the PMA system
to acquire optimal flow conditions at the inlet and has been designed for
long term experimentation, over multiple hours or days. Our LSI microfluidic
technology will generate a significant contribution to improving the design,
predictability, efficiency, and control of many NP manufacturing techniques,
thereby addressing a critical need in nanoengineering and nanomanufactur-
ing. When combined with the latest advances in the application of low-cost
and high-performance computing for production operations, this integrated
system-based approach will enable flexible and reconfigurable operations
for rapid product generation and scaling of multicomponent NPs.

10:40am Bioinspired Rotary Micromachines for Microfluidic Ap-
plications

Technical Presentation. NEMB2016-6070

Kwanoh Kim, Minliang Liu, Donglei Fan, The University of Texas
at Austin, Austin, TX, United States

Micromachines are miniaturized mechanical devices that can convert differ-
ent energy sources into controlled motion. Recently, with vigorous progress
in nanotechnology, remarkable advances have been made in the devel-
opment and application of miniaturized machines. Various working mecha-
nisms have been reported, and sensors and actuators based on micromo-
tors have been demonstrated using nanoentities with different shapes, siz-
es, and material properties. However, while those functional nanoentities are
essential to further expand the applications of micromachines, it is arduous 69
to obtain three-dimensional (3D) micro/nanostructures with complex geom-
etries and desired properties. It usually requires costly and time consuming