Microfluidic nanotechnology for chemical sensing

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Nanotechnology will be employed together with the microfluidic chip for sensing chemical compounds in my analytical chemistry research program. While the microchip provides precise and fast liquid delivery, nanotechnology improves functionality of the sensor materials to achieve sensing. There is a demand to quickly determine the compositions of chemical compounds in a liquid mixture, such as a fuel mixture consisting of gasoline and oil. Although this determination can be conducted by laboratory equipment, this goal is difficult to achieve by a simple dip-in sensor. A novel sensor, which is a nano-structured material such as the photonic crystal, will be developed. It can change color by organic liquids if they enter, and thus wet, the nano-sized pores in the nanomaterials. We will use a microfluidic method to precisely deliver reactants and control their subsequent reactions on the substrate to produce the photonic crystal-based sensor. We will examine in detail the various parameters that govern the wetting of the pores in the photonic crystals. The sensor will be in the form of a dip-in strip for simple visual testing of various commonly used fuel mixtures such as gasoline/oil (16:1) or gasoline/ethanol (95:5 or E5). The liquid compositions will change due to evaporation during storage of the fuel mixture at stores or at home, and so a simple domestic test for fuel mixture compositions will be advantageous to the general public. An important way to achieve low detection limit in sensing is to reduce nonspecific binding on a surface. Unfortunately, reduction of nonspecific adsorption will usually reduce the binding between specific probes and targets, such as proteins or oligonucleotides. Therefore, specificity is usually increased at the expense of sensitivity (low specific signal), and so the signal-to-noise ratio may remain unimproved. In my lab, we plan to resolve this issue by using 2 different approaches for analysis of proteins and DNAs. For protein analysis, a non-sticky coating is used on the surface to avoid binding of interferent substances on it and to improve the detection limit of a clinically relevant protein found in serum. For DNA analysis, gold nanoparticles are used to remove nonspecific substances without removing the analytes. We will study the mechanism of interactions of DNAs with gold nanoparticles that results in the successful removal of interferents in DNA analysis. In analytical chemistry, it is necessary to pre-concentrate reagents for fast reaction and sensitive detection. Pre-concentration can be achieved by volume reduction in which the reagents are captured on functionalized particles while the solvents are removed. The chemicals are then released in a smaller volume of liquid, essentially increasing their concentrations. The nature of particles (pore diameter, loading capacity) and the efficiency of mixing (turbulence, residence time) will be studied.