Polyelectrolyte multilayers (PEM) in micro / nanofluidics for novel BioMEMS platforms

Abstract

The overall goal of this thesis was to exploit the versatility of the polyelectrolyte multilayer (PEM) to fabricate a novel micro/nanofluidic device for patterning bacteria in BioMEMS. Nanofluidic channels offer new opportunities for advanced biomolecule manipulation and separation science because they provide unique capabilities such as ion-perm selectivity and nanometer-sized structures. In order to establish industrial applications for biotechnology and medicine, including separation of biomolecules, drug delivery, and single molecule detection, however, regular planar nanofluidic channels have limited fluidic conductance that results low throughput. Therefore, it would be important to develop a robust engineering platform with precise control of depth to the nanometer scale without channel collapse. Nanochannel-induced fluidic conduction can be enhanced by controlling the channel gap size for increasing electrical double layer (EDL) overlap as well as fabricating high-throughput vertical nanofluidic channels. We have fabricated a vertical nanofluidic channel by anisotropic etching of silicon. The gap size of the vertical nanochannel was as low as 50 nm, as obtained by layer-by-layer deposition of polyelectrolyte. Silicon-to-glass bonding was achieved by electrostatic interaction at lower temperature (180 'C) than conventional anodic bonding temperatures (300-400 C), and even at room temperature (25 C). The second part of this thesis focuses on patterning bacteria on polyelectrolyte multilayers. Patterns of bacteria are of growing interest in biofilm formation and the broader area of microbial ecology. A simple method to create functionalized surfaces for efficient micro-patterning of bacteria is presented, based on the use of micromolding in capillaries (MIMIC) of poly(ethylene glycol)-poly(lactide) diblock copolymer (PEG-PLA) onto polyelectrolyte multilayers. Two different implementations showed excellent selective antibiofouling results for micropatterning of bacteria.