Acoustically Actuated Microrotors
M. Kaynak, A. Ozcelik, N. Nama, A. Nourhani, P.E. Lammert, V. H. Crespi, T. J. Huang, Acoustofluidic actuation of in situ fabricated microrotors,
Lab Chip, 2016, 16, 3532
We have demonstrated in situ fabricated and acoustically actuated microrotors. A polymeric microrotor with predefined oscillating sharp-edge structures is fabricated in situ by applying a patterned UV light to polymerize a photocrosslinkable polyethylene glycol solution inside a microchannel around a polydimethylsiloxane axle. To actuate the microrotors by oscillating the sharp-edge structures, we employed piezoelectric transducers which generate tunable acoustic waves. The resulting acoustic streaming flows rotate the microrotors. The rotation rate is tuned by controlling the peak-to-peak voltage applied to the transducer. A 6-arm microrotor can exceed 1200 revolutions per minute. Our technique is an integration of single-step microfabrication, instant assembly around the axle, and easy acoustic actuation for various applications in microfluidics and microelectromechanical systems (MEMS).
M. Kaynak, A. Ozcelik, A. Nourhani, P.E. Lammert, V. H. Crespi, T. J. Huang, Acoustic actuation of bioinspired microswimmers, Lab Chip, 2017, 17, 395
Acoustic actuation of bioinspired microswimmers is experimentally demonstrated. Microswimmers are fabricated in situ in a microchannel. Upon acoustic excitation, the flagellum of the microswimmer oscillates, which in turn generates linear or rotary movement depending on the swimmer design. The speed of these bioinspired microswimmers is tuned by adjusting the voltage amplitude applied to the acoustic transducer. Simple microfabrication and remote actuation are promising for biomedical applications.
Cell and Organism Manipulation
A. Ozcelik, N. Nama, P.-H. Huang, M. Kaynak, M. R. McReynolds, W. Hanna-Rose and T. J. Huang, Acoustofluidic Rotational Manipulation of Cells and Organisms Using Oscillating Solid Structures, Small, 2016, 12, 5120.
We have demonstrated precise in-plane and out-of-plane rotational manipulation of single HeLa cells and C. elegans using acoustic microstreaming flows generated by oscillating sharp-edge structures and glass slide under the microchannel. Dynamic control of rotational manipulation is achieved using short pulses of sine waves to adjust the angular position. The OLQ neuron cells located in the head of an L4 stage C. elegans are observed through the rotational manipulation. Using sharp-edge structures, single cell rotation rates exceeding 14,000 rpm are realized. As a potential application, effective tailoring of the rotational speed could be utilized to apply adjustable shear forces to single cells. Furthermore, out-of-plane rotation of single cells and model organisms like C. elegans is an indispensable tool for comprehensive bioimaging capabilities. Our acoustofluidic rotational manipulation device is simple-to-fabricate and easy-to-operate. It can be conveniently integrated into the existing microfluidic devices designed for handling cells and small model organisms.
Micromixing of High-Viscous Fluids
S. Orbay, A. Ozcelik, J. Lata, M. Kaynak, M. Wu, and T. J. Huang, Mixing high-viscosity fluids via acoustically driven bubbles, J. Micromech. Microeng. 27 (2017) 015008
We present an acoustofluidic micromixer which can perform rapid and homogeneous mixing of highly viscous fluids in the presence of an acoustic field. In this device, two highviscosity polyethylene glycol (PEG) solutions were co-injected into a three-inlet PDMS microchannel with the center inlet containing a constant stream of nitrogen flow which forms bubbles in the device. When these bubbles were excited by an acoustic field generated via a piezoelectric transducer, the two solutions mixed homogenously due to the combination of acoustic streaming, droplet ejection, and bubble eruption effects. The mixing efficiency of this acoustofluidic device was evaluated using PEG-700 solutions which are ~106 times more viscous than deionized (DI) water. Our results indicate homogenous mixing of the PEG-700 solutions with a ~0.93 mixing index. The acoustofluidic micromixer is compact, inexpensive, easy to operate, and has the capacity to mix highly viscous fluids within 50 ms.