Thermal microfluidic devices: Design, fabrication and applications.

摘要

This thesis investigates the thermal actuation and temperature measurement methods in microfluidic devices. We designed and fabricated microfluidic devices with various functionalities such as: bio sensing, particle counting, microscale calorimetry, and cellular temperature measurement. All of these functionalities use thermal measurement methods.;When quantitative measurements are required, the label-free nature of thermal measurement methods, along with its simple readout, make it a powerful candidate for lab on a chip and bio sensing/detection applications. In this work, thermal measurement methods are used to characterize bio-samples, measure concentrations, study thermal responses, and even perform particle cytometry.;However, thermal measurement methods are known for their low speed and low sensitivity characteristics, which are influenced by thermal properties of materials and structural design. On the microscale, we designed and fabricated microfluidic structures with modified thermal properties to achieve low response times and high sensitivity. To optimize our devices, we analyzed the thermal responses of the designed structures using a first order equivalent electrical circuit model. We then compared the results of the model to the fabricated device responses. To increase the functionality of our device, we used a number of temperature measurement techniques; thermal wave analysis, AC calorimetry, time of flight measurement, and the continuous recording of differential temperature.;In this work, we fabricated an on-chip calorimeter with a 200 nL chamber volume and measured specific heat and thermal conductivity of water and glycerol. Also, we measured the thermal properties of the ionic liquids with the calorimeter. Moreover, we fabricated a calorimetric microfluidic biosensor to detect and measure the glucose levels of blood with concentrations of 0.05 to 0.3% wt/vol. We applied the same method to measure DNA concentration in buffer solution and a protein binding reaction. Also, we developed a method to count the number of particles passing through a micro channel while simultaneously measuring the size deference between particles by measuring changes in thermal conductivity. We fabricated a microfluidic platform to capture a single cell to measure the temperature of the cell in response to an external stimulation.