25 research outputs found
Cell separation using tilted-angle standing surface acoustic waves
Separation of cells is a critical process for studying cell properties, disease diagnostics, and therapeutics. Cell sorting by acoustic waves offers a means to separate cells on the basis of their size and physical properties in a label-free, contactless, and biocompatible manner. The separation sensitivity and efficiency of currently available acoustic-based approaches, however, are limited, thereby restricting their widespread application in research and health diagnostics. In this work, we introduce a unique configuration of tilted-angle standing surface acoustic waves (taSSAW), which are oriented at an optimally designed inclination to the flow direction in the microfluidic channel. We demonstrate that this design significantly improves the efficiency and sensitivity of acoustic separation techniques. To optimize our device design, we carried out systematic simulations of cell trajectories, matching closely with experimental results. Using numerically optimized design of taSSAW, we successfully separated 2- and 10-Āµm-diameter polystyrene beads with a separation efficiency of ~99%, and separated 7.3- and 9.9-Āµm-polystyrene beads with an efficiency of ~97%. We illustrate that taSSAW is capable of effectively separating particlesācells of approximately the same size and density but different compressibility. Finally, we demonstrate the effectiveness of the present technique for biologicalābiomedical applications by sorting MCF-7 human breast cancer cells from nonmalignant leukocytes, while preserving the integrity of the separated cells. The method introduced here thus offers a unique route for separating circulating tumor cells, and for label-free cell separation with potential applications in biological research, disease diagnostics, and clinical practice.National Institutes of Health (U.S.) (Grant U01HL114476)National Institutes of Health (U.S.) (New Innovator Award 1DP2OD007209-01)National Science Foundation (U.S.). Materials Research Science and Engineering Centers (Program) (Grant DMR-0820404
Design of a Variable Thickness Plate to Focus Bending Waves
This paper describes the design of a thin plate whose thickness is tailored in order to focus bending waves to a desired location on the plate. Focusing is achieved by smoothly varying the thickness of the plate to create a type of lens, which focuses structural-borne energy. Damping treatment can then be positioned at the focal point to efficiently dissipate energy with a minimum amount of treatment. Numerical simulations of both bounded and unbounded plates show that the design is effective over a broad frequency range, focusing traveling waves to the same region of the plate regardless of frequency. This paper also quantifies the additional energy dissipated by local damping treatment installed on a variable thickness plate relative to a uniform plate
Optofluidic tunable microlens by manipulating the liquid meniscus using a flared microfluidic structure
We have designed, demonstrated, and characterized a simple, novel in-plane tunable optofluidic microlens. The microlens is realized by utilizing the interface properties between two different fluids: CaCl2solution and air. A constant contact angle of ā¼90Ā° is the pivotal factor resulting in the outward bowing and convex shape of the CaCl2 solution-air interface. The contact angle at the CaCl2 solution-air interface is maintained by a flared structure in the polydimethylsiloxane channel. The resulting bowing interface, coupled with the refractive index difference between the two fluids, results in effective in-plane focusing. The versatility of such a design is confirmed by characterizing the intensity of a traced beam experimentally and comparing the observed focal points with those obtained via ray-tracing simulations. With the radius of curvature conveniently controlled via fluid injection, the resulting microlens has a readily tunable focal length. This ease of operation, outstandingly low fluid usage, large range tunable focal length, and in-plane focusing ability make this lens suitable for many potential lab-on-a-chip applications such as particle manipulation, flow cytometry, and in-plane optical trapping
Single-Shot Characterization of Enzymatic Reaction Constants <i>K</i><sub>m</sub> and <i>k</i><sub>cat</sub> by an Acoustic-Driven, Bubble-Based Fast Micromixer
In this work we present an acoustofluidic approach for
rapid, single-shot
characterization of enzymatic reaction constants <i>K</i><sub>m</sub> and <i>k</i><sub>cat</sub>. The acoustofluidic
design involves a bubble anchored in a horseshoe structure which can
be stimulated by a piezoelectric transducer to generate vortices in
the fluid. The enzyme and substrate can thus be mixed rapidly, within
100 ms, by the vortices to yield the product. Enzymatic reaction constants <i>K</i><sub>m</sub> and <i>k</i><sub>cat</sub> can then
be obtained from the reaction rate curves for different concentrations
of substrate while holding the enzyme concentration constant. We studied
the enzymatic reaction for Ī²-galactosidase and its substrate
(resorufin-Ī²-D-galactopyranoside) and found <i>K</i><sub>m</sub> and <i>k</i><sub>cat</sub> to be 333 Ā±
130 Ī¼M and 64 Ā± 8 s<sup>ā1</sup>, respectively,
which are in agreement with published data. Our approach is valuable
for studying the kinetics of high-speed enzymatic reactions and other
chemical reactions
An integrated, multiparametric flow cytometry chip using āmicrofluidic driftingā based three-dimensional hydrodynamic focusing
In this work, we demonstrate an integrated, single-layer, miniature flow cytometry device that is capable of multi-parametric particle analysis. The device integrates both particle focusing and detection components on-chip, including a āmicrofluidic driftingā based three-dimensional (3D) hydrodynamic focusing component and a series of optical fibers integrated into the microfluidic architecture to facilitate on-chip detection. With this design, multiple optical signals (i.e., forward scatter, side scatter, and fluorescence) from individual particles can be simultaneously detected. Experimental results indicate that the performance of our flow cytometry chip is comparable to its bulky, expensive desktop counterpart. The integration of on-chip 3D particle focusing with on-chip multi-parametric optical detection in a single-layer, mass-producible microfluidic device presents a major step towards low-cost flow cytometry chips for point-of-care clinical diagnostics
Class and the northern seas
SIGLEAvailable from British Library Document Supply Centre-DSC:9348.749(7) / BLDSC - British Library Document Supply CentreGBUnited Kingdo
An On-Chip, Multichannel Droplet Sorter Using Standing Surface Acoustic Waves
The
emerging field of droplet microfluidics requires effective
on-chip handling and sorting of droplets. In this work, we demonstrate
a microfluidic device that is capable of sorting picoliter water-in-oil
droplets into multiple outputs using standing surface acoustic waves
(SSAW). This device integrates a single-layer microfluidic channel
with interdigital transducers (IDTs) to achieve on-chip droplet generation
and sorting. Within the SSAW field, water-in-oil droplets experience
an acoustic radiation force and are pushed toward the acoustic pressure
node. As a result, by tuning the frequency of the SSAW excitation,
the position of the pressure nodes can be changed and droplets can
be sorted to different outlets at rates up to 222 droplets s<sup>ā1</sup>. With its advantages in simplicity, controllability, versatility,
noninvasiveness, and capability to be integrated with other on-chip
components such as droplet manipulation and optical detection units,
the technique presented here could be valuable for the development
of droplet-based micro total analysis systems (Ī¼TAS)
An On-Chip, Multichannel Droplet Sorter Using Standing Surface Acoustic Waves
The
emerging field of droplet microfluidics requires effective
on-chip handling and sorting of droplets. In this work, we demonstrate
a microfluidic device that is capable of sorting picoliter water-in-oil
droplets into multiple outputs using standing surface acoustic waves
(SSAW). This device integrates a single-layer microfluidic channel
with interdigital transducers (IDTs) to achieve on-chip droplet generation
and sorting. Within the SSAW field, water-in-oil droplets experience
an acoustic radiation force and are pushed toward the acoustic pressure
node. As a result, by tuning the frequency of the SSAW excitation,
the position of the pressure nodes can be changed and droplets can
be sorted to different outlets at rates up to 222 droplets s<sup>ā1</sup>. With its advantages in simplicity, controllability, versatility,
noninvasiveness, and capability to be integrated with other on-chip
components such as droplet manipulation and optical detection units,
the technique presented here could be valuable for the development
of droplet-based micro total analysis systems (Ī¼TAS)