| Summary: | Calorimetry is a very effective technique employed for analyzing biochemical reactions (glucose and urea sensing, DNA detection and biodefense). Most of the commercial micro-calorimetric sensors available in the market don't have either a simple operational configuration (amperometric sensors which rely on a detection of ions in a solution based on changes in electric current), or can only detect temperature changes in the range of 0.1-0.2 K. The most important performance
metrics that ought to be considered for the design and optimization of micro-calorimetric biochemical sensors are the thermal detection capabilities of the sensing element and the thermal coupling between the biochemical reaction and the thermal detector. All these fundamental challenges are addressed in this thesis by taking advantage of advanced material properties and innovative device engineering, the result of which are high temperature resolution (994.5
µK/Hz1/2 in a 50 Hz measurement bandwidth and 534.355 µK/Hz1/2 in a 200 Hz measurement bandwidth) micro-calorimetric sensors based on high frequency (134.5 MHz and 116.67 MHz) Aluminum Nitride (AlN) nano-plate resonators (NPR), overlapped by a freestanding reaction chamber separated by a micro-scale air gap (~50 µm). High sensitivity (~8.66 ppm/K and ~22.2 ppm/K) and low noise performance (~1.16 Hz/Hz1/2 in
a 50 Hz bandwidth) are achieved by scaling the overall volume of the resonant structure and by taking advantage of two high quality factor, Q (~882 and ~985), resonant systems. Efficient thermal coupling between the biochemical reaction and the resonant thermal detector is achieved by reducing to ~50 µm the air gap between the resonator and the freestanding reaction chamber. The non - contact measurement also reduces the degradation of performance metrics like mass loading
effects.
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