| Chemical signals manifested by messenger molecules are omnipresent in the life sciences. The ability to generate such chemical and biological signals artificially in microscale will be an enabling factor in probing, understanding, controlling and regulating complex biological systems.;Microfluidics with many advantages such as consumption of small volume of sample and reagents, having a low cost, offer faster response and have a small footprint. In this dissertation, for the first time, the design, fabrication and testing of different architectures of microfluidic chemical concentration signal generators inspired by Digital to Analog Converters (DAC) are thoroughly studied. These chemical concentration signals generators are often called Concentration Digital to Analog Converter or C-DAC. The main idea is to generate binary weighted streams of chemical concentration signals and then select, direct and intermix those streams of concentration signals to the output based the value of digital input code generated by a computer program. Three different architectures which are developed in this research are based dilution networks, Pulse Code Modulators (PCM) and Multi-Plug Modulators (MPM).;Modeling and simulation of microfluidic devices with hundreds of components at system level using conventional computational fluid dynamic (CFD) methods is very challenging and often impractical. A new lumped model which is inclusive of dispersion and convection is developed based on one-dimensional discretization of the convectiondiffusion equation. The model which is implemented using Verilog-AMS is capable of tracking the transport of solvent and solute inside a microfluidic system using four dual-branch lumped nodal quantities of solvent pressure, solvent flow rate, solute concentration and solute current. The simulation results of Lab On Chip SIMulator tool (or simply LOCSIM) are in a very good agreements with the experimental results.;The chemical concentration signal generators are used to design a combinatorial multicomponent plug mixer (CMPM) chip for drug discovery application. The CMPM chip is capable of generating a large number of mix ratios of four different components. The CMPM chip has used to study ribonucleotide reductase (RNR) protein-protein/protein-ligand interaction networks and was tested to produce fluorescent dye and dihydrofolate reductase NADPH/MX mixtures with plug lengths of 2 mm.;In another application, a 1-bit PCM C-DAC chip (PCM chip) is used to chemically stimulate the nervous system in Aplysia Californica. In this application, chemical neurostimulation is performed to cereberal ganglion using the PCM chips and the neural activities are recorded extracellularly from buccal ganglion. The chip excitation with the agonist carbachol was successful in artificially inducing ingestive motor programs. |
