Browsing by Subject "Particle Manipulation"
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Item Open Access Exploiting the Interplay of Acoustic Waves and Fluid Motion for Particle Manipulation(2021) Gu, YuyangAcoustofluidics is an emerging research field that combines both acoustics and fluid dynamics. With acoustic tweezers technique being developed for years, it is featured for its contactless, noninvasive, and biocompatibility which makes the method suitable for various applications in the field of biology, material sciences, and chemistry. Especially when handling small objects, e.g., cells, nanoparticles, C. elegans, and zebrafish larvae, the native environment involved is mainly liquid. During the acoustic propagation inside the liquid, fluid motion will also be initiated and will influence the object movement in addition to the acoustic radiation forces. This brings up the multidisciplinary study combining the acoustic wave and fluid motion for object manipulation within liquids. This technical development has revealed huge potential for applying acoustofluidic studies into different applications. However, there are still several technical bottlenecks that must be overcome for acoustofluidic technology to provide maximum impact. For example, cell patterning using standing acoustic waves commonly has the regular grid-like shape and sees the fluid motion as an unwanted side effect without an effective way to minimize it. The current target particle size that can be controlled using acoustics is between ~mm to µm, thus hindering the exploration of nanoscale objects. In this dissertation, I explored the combined effect of acoustics and fluid dynamics, and validated that the interplay of both effects can derive new research insights and can be applied to particles with a smaller size range (i.e., nanometer). Specifically, I studied the synergetic effect of acoustics and flow in three classic fluid systems: bulk fluids, droplets, and continuous flow. For bulk fluids, we designed an acoustofluidic holography platform that can initiate and utilize fluid motion with arbitrary designed acoustic fields. With the design and implementation of the holographic acoustic lens, our method can pattern cells into an arbitrary shape that can potentially benefit tissue engineering or cell mechanics studies. Besides patterning, we also demonstrated that, with the same experimental configuration, we can utilize vortex acoustic streaming to achieve different functions, e.g., particle rotation, concentration, and separation. For droplets, we observed a new physics phenomenon which can drive the spin of a liquid droplet using surface acoustic wave. With this external angular momentum and Stokes drift effect, we found the nanoparticles can be rapidly concentrated or differentially concentrated in one spinning droplet. Furthermore, we demonstrated that the single spinning droplet can serve as one unit that possesses a specific function and we can assemble the units for a more flexible manipulation function. We built a dual droplet acoustofluidic centrifuge system that can achieve nanoparticle separation and transport and utilized the platform for exosome subgroup separation. For continuous flow, as acoustic separation technique has been developed for years, we have explored two directions that may be utilized for small animal blood apheresis study. One direction is the high-throughput platelet separation using a plastic device. This method significantly increased the throughput and moved one step towards clinical usage. Another direction is building the integrated system for plasma separation. Built around the surface acoustic wave separator, we assembled the fluid driving unit, temperature control unit, and separation unit into a prototype-like system. We then performed the proof-of-concept experiment to identify the feasibility of applying the acoustofluidic separation method to small animal models (i.e., mice).
Item Open Access Magnetomicrofluidics Circuits for Organizing Bioparticle Arrays(2017) Abedini Nassab, RoozbehSingle-cell analysis (SCA) tools have important applications in the analysis of phenotypic heterogeneity, which is difficult or impossible to analyze in bulk cell culture or patient samples. SCA tools thus have a myriad of applications ranging from better credentialing of drug therapies to the analysis of rare latent cells harboring HIV infection or in Cancer. However, existing SCA systems usually lack the required combination of programmability, flexibility, and scalability necessary to enable the study of cell behaviors and cell-cell interactions at the scales sufficient to analyze extremely rare events. To advance the field, I have developed a novel, programmable, and massively-parallel SCA tool which is based on the principles of computer circuits. By integrating these magnetic circuits with microfluidics channels, I developed a platform that can organize a large number of single particles into an array in a controlled manner.
My magnetophoretic circuits use passive elements constructed in patterned magnetic thin films to move cells along programmed tracks with an external rotating magnetic field. Cell motion along these tracks is analogous to the motion of charges in an electrical conductor, following a rule similar to Ohm’s law. I have also developed asymmetric conductors, similar to electrical diodes, and storage sites for cells that behave similarly to electrical capacitors. I have also developed magnetophoretic circuits which use an overlaid pattern of microwires to switch single cells between different tracks. This switching mechanism, analogous to the operation of electronic transistors, is achieved by establishing a semiconducting gap in the magnetic pattern which can be changed from an insulating state to a conducting state by application of electrical current to an overlaid electrode. I performed an extensive study on the operation of transistors to optimize their geometry and minimize the required gate currents.
By combining these elements into integrated circuits, I have built devices which are capable of organizing a precise number of cells into individually addressable array sites, similar to how a random access memory (RAM) stores electronic data. My programmable magnetic circuits allow for the organization of both cells and single-cell pairs into large arrays. Single cells can also potentially be retrieved for downstream high-throughput genomic analysis.
In order to enhance the efficiency of the tool and to increase the delivery speed of the particles, I have also developed microfluidics systems that are combined with the magnetophoretic circuits. This hybrid system, called magnetomicrofluidics, is capable of rapidly organizing an array of particles and cells with the high precision and control. I have also shown that cells can be grown inside these chips for multiple days, enabling the long-term phenotypic analysis of rare cellular events. These types of studies can reveal important insights about the intercellular signaling networks and answer crucial questions in biology and immunology.