Design, fabrication and testing of silicon microneedle-based microfabricated biomedical devices

Presented in this dissertation are two distinct Microelectromechanical Systems (MEMS) based microdevices: Wound Potential Measuring Device and Transdermal Fluid Transport Device. Both devices utilized similar fabrication techniques to create their functional microneedle structures, but the end result of each microneedle array was extremely different in function form one another.; A novel MEMS device was pursued as a reliable, repeatable, wound potential measuring device. The design, fabrication and preliminary testing of an individually addressable, micro-needle array for the measurement of endemic electric fields in wounded tissue are presented. In vivo animal and in vitro testing of keratinocytes (the first cellular response to wound healing) has shown cathodally-directed migration in physiological DC electrical fields (100–200 mV/mm). Results from human wound studies are less forthcoming due to mechanical fragility inherent with standard drawn glass electrode probes. Photolithography, thin-film metal deposition, anodic bonding, dicing saw and wet chemical etching produced an array of silicon micro-needles bonded to an electrically insulating glass substrate with Pt electrodes addressing individual needles that are sharp enough to pierce skin yet robust enough to withstand multiple penetrations with minimal tip damage. Wound-induced transdermal potential changes measured by the microdevice show similar trends to animal studies reported in the literature.; A MEMS based transdermal fluid transport device was also fabricated using technologies developed for microneedle array fabrication. A minimally invasive method for sampling biological fluids is a prerequisite to performing either periodic or continuous monitoring of physiological systems. In particular, blood and cellular interstitial fluid (ISF) contain important metabolic and immunological biomolecules whose time varying concentrations are important indicators of various states of health and disease. The microneedle array presented here is integrated with connecting microchannels and a common reservoir, creating a generic platform, which is suitable for the inclusion of microsensors and microfluidic control devices. The needles are demonstrated to be effective in puncturing human skin and capable of extracting and delivering interstitial fluid (ISF) and whole blood to the microchannels. Verification of the extraction of ISF is made by in situ detection of glucose.