Daniel Ahmed,* Adem Ozcelik,* Nagagireesh Bojanala,  Nitesh Nama,  Awani Upadhyay,  Yuchao Chen, Wendy Hanna-Rose, and Tony Jun Huang, Rotational manipulation of single microparticles, cells, and organisms using acoustic waves, Nature Communications, 7, 110852016.  *equal contribution
​The precise rotational manipulation of single cells or organisms is invaluable to many applications in biology, chemistry, physics, and medicine. In this article, we describe an acoustic based, on-chip manipulation method that can rotate single microparticles, cells, and organisms. To achieve this, we trapped microbubbles within predefined sidewall microcavities inside a microchannel. In an acoustic field, trapped microbubbles were driven into oscillatory motion generating steady microvortices which were utilized to precisely rotate colloids, cells and entire organisms (i.e.C. elegans). We have tested the capabilities of our method by analysing reproductive system pathologies and nervous system morphology in C. elegans. Using our device, we revealed the underlying abnormal cell fusion causing defective vulval morphology in mutant worms. Our acoustofluidic rotational manipulation (ARM) technique is an easy-to-use, compact, and biocompatible method, permitting rotation regardless of optical, magnetic, or electrical properties of the sample under investigation.

Acoustofluidic Rotational Manipulation of Cells and Organisms Using Oscillating Solid Structures

Schematic and the working principle of the acoustofluidic rotational manipulation device. (a) A simple PDMS channel contains both sharp-edge and bare regions for the cell and worm rotation, respectively. Oscillations of (b) PDMS sharp-edge structures and (c) glass slide generate circulating streaming flows that are used for rotational manipulation.
​Controllable rotational manipulation enables multi-dimensional imaging and rapid screening of single cells and model organisms. Current approaches to rotationally maneuver small objects depend on optical, magnetic, or electrical properties of the sample under investigation. This dependence renders the existing methods sample-specific which limits their applicability. Here we present a new rotational manipulation method based on oscillating sidewall sharp-edge microstructures and thin glass slides in a microchannel. This method is independent of the intrinsic properties of sample under investigation and can be effectively applied to particles, cells, and multicellular organisms.
Observation of OLQ head neuron cells of an L4 stage C. elegans. (a) Bright-field and fluorescence images of ocr-4::GFP transgenic animal are overlapped in order to show the position of (b) the OLQ dorsal L (OLQDL) and ventral L (OLQVL) neurons in the head of the worm. By rotational adjustment, the paired R OLQ neurons are gradually visualized simultaneously: (c) OLQDL, OLQVL and OLQDR, and (d) OLQDL, OLQVL, OLQDL and OLQDR. 

Adem Ozcelik, Nitesh Nama, Po-Hsun Huang, Murat Kaynak, Melanie R. McReynolds, Wendy Hanna-Rose, and Tony Jun Huang, Acoustofluidic rotational manipulation using oscillating solid structures, Small, 2016. DOI: 10.1002/smll.201601760

An Acoustofluidic Micromixer via Bubble Inception and Cavitation from Microchannel Sidewalls

During the deep reactive ion etching process, the sidewalls of a silicon mold feature rough wavy structures, which can be transferred onto a polydimethylsiloxane (PDMS) microchannel through the soft lithography technique. In this article, we utilized the wavy structures of PDMS microchannel sidewalls to initiate and cavitate bubbles in the presence of acoustic waves. Through bubble cavitation, this acoustofluidic approach demonstrates fast, effective mixing in microfluidics. We characterized its performance by using viscous fluids such as poly(ethylene glycol) (PEG). When two PEG solutions with a resultant viscosity 54.9 times higher than that of water were used, the mixing efficiency was found to be 0.92, indicating excellent, homogeneous mixing. The acoustofluidic micromixer presented here has the advantages of simple fabrication, easy integration, and capability to mix high-viscosity fluids (Reynolds number: ∼0.01) in less than 100 ms.

Adem Ozcelik, Daniel Ahmed, Yuliang Xie, Nitesh Nama, Zhiguo Qu, Ahmad Ahsan Nawaz, Tony Jun Huang, An acoustofluidic micromixer via bubble inception and cavitation from microchannel sidewalls, , Analytical Chemistry, 86 (10), 5083-5088, 2014

Acousto-plasmofluidics: Acoustic modulation of surface plasmon resonance in microfluidic systems

We acoustically modulated the localized surface plasmon resonances (LSPRs) of metal nanostructures integrated within microfluidic systems. An acoustically driven micromixing device based on bubble microstreaming quickly and homogeneously mixes multiple laminar flows of different refractive indices. The altered refractive index of the mixed fluids enables rapid modulation of the LSPRs of gold nanodisk arrays embedded within the microfluidic channel. The device features fast response for dynamic operation, and the refractive index within the channel is tailorable. With these unique features, our “acousto-plasmofluidic” device can be useful in applications such as optical switches, modulators, filters, biosensors, and lab-on-a-chip systems.

Daniel Ahmed, Xiaolei Peng, Adem Ozcelik, Yuebing Zheng, Tony Jun Huang, Acousto-Plasmofluidics: Acoustic Modulation of Surface Plasmon Resonance in Microfluidic Systems, AIP Advances, 5 (9), 097161, 2015.

Acoustofluidic coating of particles and cells

On-chip microparticle and cell coating technologies enable a myriad of applications in chemistry, engineering, and medicine. Current microfluidic coating technologies often use magnetic labeling and deflection of particles across laminar streams of chemicals. Herein, we introduce an acoustofluidic approach for microparticle and cell coating by implementing tilted-angle standing surface acoustic waves (taSSAWs) in microchannels with multiple inlets. To achieve this, we exploited the primary acoustic radiation force generated from the taSSAW field to migrate the particles across the microchannel through multiple laminar streams which contained buffer and coating chemicals. We demonstrate effective coating of polystyrene microparticles and HeLa cells without the requirement of magnetic labelling. We characterized the coated particles and HeLa cells with fluorescence microscopy and scanning electron microscopy. Our acoustofluidic-based method is label-free, biocompatible, and simple. It can be applied to on-chip manufacturing of many functional particles and cells.

Bugra Ayan, Adem Ozcelik, Shi-Yang Tang, Yuliang Xie, Mengxi Wu, Peng Li and Tony Jun Huang, Acoustofluidic coating of particles and cells, Lab on a Chip, DOI: 10.1039/c6lc00951d

Acoustofluidic Actuation of In Situ Fabricated Microrotors

Murat Kaynak, Adem Ozcelik, Amir Nourhani, Nitesh Nama, Paul E. Lammert, Vincent H. Crespi, and Tony Jun Huang,  Acoustofluidic Actuation of In Situ Fabricated Microrotors, Lab on Chip, 16 (18), 3532-3537, 2016

We have demonstrated in situ fabricated and acoustically actuated microrotors. A polymeric microrotor with predefined beak structures is fabricated by applying a patterned UV light through a photocro[AO1] sslinkable [VC2] polyethylene glycol (PEG) solution and polymerizing inside a microchannel while in-place around a polydimethylsiloxane (PDMS) axle. Piezoelectric transducers (PZTs) generate tunable acoustic waves which actuate the microrotors by oscillating the beak structures and thus generating acoustic streaming. The thrust generated by the acoustic streaming flows rotates the microrotors with a tunable rotational rate controlled by the peak-to-peak voltage applied to the transducer. A 6-armed microrotor can exceed 1200 RMP. This technique is an integration of single-step microfabrication, instant assembly around the PDMS axle, and easy actuation. These acoustic driven microrotors can be used in various applications including micropumps, micromixers, and microgears.

Acoustic Actuation of Bioinspired Microswimmers

Murat Kaynak, Adem Ozcelik, Paul E. Lammert, Amir Nourhani, Vincent H. Crespi, and Tony Jun Huang, Acoustic Actuation of Bioinspired Microswimmers, Lab on a Chip,17, 395-400, 2017. 

We have demonstrated in situ fabrication and acoustic actuation of flagellated rotational and linear microswimmers which are inspired by flagellated biological microswimmers. For the former, sustained clockwise or counterclockwise rotation can be maintained by using swimmers that are resistant to flipping over within the microchannel. For the latter, we designed microswimmers with a head and a tail which is inspired by the geometry of a bacterial flagellum. The flagella oscillate under acoustic field and thus generate acoustically driven streaming that drives the microswimmers. The linear microswimmers reach ~1200 μm/s, while rotational microswimmers rotate at 200 RPM. The simple, durable, biocompatible and inexpensive fabrication and remote actuation of these biologically inspired microswimmers show potential for various applications in physics, biochemistry, and biomedical engineering, such as targeted drug delivery, fluid manipulation, micro assembly, cell manipulation, microsurgery, and chemical analysis.
Scroll to top