Date of Award
Doctor of Philosophy (PhD)
Acoustofluidics combine ultrasonic actuation with small-volume microfluidic channels to enable precise, contactless object manipulation for a range of applications from serial chemical processing to blood component separation and single-cell analysis. Micron- to millimeter-scale vibrational waves generate reproducible pressure fields within the microfluidic channels and chambers. By exploiting the material property mismatch between a particle (polymeric and silica beads, cells, etc.) and a suspending fluid, the acoustic radiation force is used to move particles toward regions of low (nodes) or high pressure (antinodes). An understanding of these field-particle interactions is applied to design and implement complicated channel architectures for preferential segregation or immobilization of particles within regions of interest.The reported work demonstrates a new class of acoustofluidic device that utilizes longitudinal standing bulk acoustic waves (LSBAW) and structure-dependent augmentation of the pressure field at prescribed locations for serial chemical and biological synthesis. By engineering novel pillar arrays within the microchannel, the field is locally amplified and developed orthogonal to the direction of reagent flow. This field configuration retains microparticles to act as substrates for surface chemical reactions involving the nanoscale reagents. Operating frequencies are dictated by the geometry of the channel and the composition of the fluid. Predictive computational models are used to design and optimize microdevices that are well-suited to specific applications. Here, LSBAW devices are shown to be effective tools for conjugation of antibodies to payload molecules, as well as for the detection of biomarkers for chronic obstructive pulmonary disease (COPD).To address the need for a simplified method to develop custom antibody constructs (e.g., antibody-drug conjugates (ADC) and antibody-tracer conjugates (ATCs)), the LSBAW platform was created to allow continuous surface modification of the substrates for sensitive reactions that comprise alternating flows of chemical modifiers and buffer solutions. By testing microparticles of differing size, porosity, and composition, the overall antibody construct yield was improved while exhibiting the broad applicability of the platform to alternative substrates without modification of the channel design. The LSBAW device effectively attached, modified, and released the antibodies from the microparticle surface for collection. Finally, using the intermediary synthetic step of antibody terminated microparticles, a modified immunoassay was developed for the detection of COPD antigens from free-flowing solutions of cell lysate. Rather than the conventional method of enzyme immunosorbent assays (ELISA), which requires tedious manual processing, the LSBAW device shows the beginnings of an automated method of protein detection in a multiplexed channel for low-concentration solutions (ng/mL).
John M. Meacham
Mikhail Y. Berezin, Michael J. Holtzman, Amit Pathak, Srikanth Singamaneni,
Available for download on Friday, December 15, 2119