ABSTRACTOrganically modified silica gels and dye-doped silica gels have been
patterned into micrometer-scale structures on a substrate using micro
molding in capillaries (MIMIC). This approach is from a class of elastomeric
stamping and molding techniques collectively known as soft lithography. Soft
lithography and sol-gel processing share attractive features in that they
are relatively benign processes performed at ambient conditions, which makes
both techniques compatible with a wide variety of organic molecules,
molecular assemblies, and biomolecules. The combination of sol-gel and soft
lithography, therefore, holds enormous promise as a tool for
microfabrication of materials with optical, chemical, or biological
functionality that are not readily patterned with conventional methods. This
paper describes our investigation of micro-patterned organic-inorganic
hybrid materials containing indicator dyes for microfluidic sensor
applications. Reversible colorimetric pH sensing via entrapped reagents is
demonstrated in a prototype microfluidic sensor element. Patterned
structures range from one to tens of micrometers in cross-section and are up
to centimeters in length. Fundamental chemical processing issues associated
with mold filling, cracking and sensor stability are discussed.
A fourth-order single-bit switched-capacitor sigma-delta modulator for distributed sensor applications