Biomedical Circuits and Signal Analysis Systems for Measurement within Microsystems

Microsystems are especially well-suited to the study of biological tissues, cells, microbials, and molecules, due to their capability for enabling microfluidic separation towards selective enrichment, high levels of parallelization, and highly sensitive spatially and temporally resolved measurements. However, current innovations to enhance biomedical measurements are chiefly focused in the sphere of materials chemistry and device design. We seek to advance biomedical measurements within microsystems integrating key technologies from electronics and signal analysis fields.
Conventional techniques for cell separation are predominantly based on hydrodynamic methods applied to fluorescence- and magnetic-activated cell sorting. However, these techniques suffer from a lack of specificity, high cell loss, use of labels, and high capital/operating cost. Dielectrophoresis (DEP) over an insulator layer (iDEP) or contact-less DEP (cDEP) offers unique advantages for the sorting and analysis of biosystems due to its label-free ability for selective transport based on inherent dielectric properties, which can advance usability, throughput, and efficiency of cell separations. One of the main bottlenecks in iDEP-based cell separation is the physical separation of the electrodes from the sample for reducing the destruction of cells, leads to the need for a higher voltage AC signal (>100 V_RMS) at MHz level. Furthermore, the microfluidic device geometry and architecture of the sample and electrode channels need to be optimized to maximize the fraction of the applied voltage available for DEP manipulation.
Despite the technological capabilities of forensic laboratories, the backlog in samples await DNA analysis has become a severe problem. This ever-growing backlog will not be reduced without new techniques that provide automation and enhanced throughput.
This dissertation is focused on the design and implementation of electronic circuits and signal analysis systems to address the current limitations in a variety of micro- or bioanalytical systems. Innovations presented here include designing a wideband high voltage AC generator that addresses the performance degradation of commercial amplifiers, an impedance analyzer for optimization of frequency-selective electrokinetic manipulation in microfluidic systems, and a compact and more efficient circuit for real-time tracking of resonance frequency for sample manipulation by acoustophoresis.