Polymer-based microfluidic platforms have great potential for use in BioMEMS applications because many polymers are low cost, biocompatible, and have good processibility. However, packaging (i.e., sealing the platform with a lid) is a challenging issue in their fabrication. In this paper, we compare several available bonding techniques such as adhesive tape bonding and chemical-assisted bonding with a new method recently developed in our lab: resin-gas injection-assisted bonding. This new approach can easily seal microfluidic devices with micron and sub-micron sized channels without blocking the flow path. It can also be used to modify the channel shape, size, and surface characteristics (e.g., hydrophilicity, degree of protein adsorption). By applying the masking technique, local modification of the channel surface can be achieved through cascade resin-gas injection. Experiments are carried out to demonstrate the bonding efficiency and surface modification.
The genetically-modified binding proteins calmodulin, the phosphate binding protein, the sulfate binding protein, and the galactose/glucose binding protein have been successfully employed as biosensing elements for the detection of phenothiazines, phosphate, sulfate, and glucose, respectively. Mutant proteins containing unique cysteine residues were utilized in the site-specific labeling of environment-sensitive fluorescent probes. Changes in the environment of the probes upon ligand-induced conformational changes of the proteins result in changes in fluorescence intensity.