Micromachining: A new direction for clinical analyzers

Conventional analytical reactions are performed in test tubes, but in the future, reactions may be routinely performed in minute chambers micromachined in small silicon or glass chips. Disposable micromachined devices are : easily designed, low cost, small, portable, easy and fast to operate, use micro volumes of sample and reagents, are adaptable for simultaneous multiple-assays, and provide system integration. We have constructed micromachined devices for semen analysis, in vitro fertilization (IVF), PCR, and immunoassay. The key structural element of the sperm chips (silicon-glass and glass-glass) is a tortuous channel for assessment of sperm motility. IVF chips consist of a semen application chamber and an egg nesting chamber separated by a tortuous sperm selection channel. Chips were evaluated for IVF using the mouse model, and fertilization and growth from 2 cell to the blastocyst stage was successfully demonstrated. Silicon-glass chips containing 40-80 um deep micro-chambers were effective for PCR reactions. Excellent thermal conductivity of the silicon, plus the high surface/volume ratio (>20 mm(2)/uL) provides efficient heat transfer. This PCR chip (volume, approx 10 uL) was successfully used to amplify a range of targets (e.g., bacteriophage lambda, Campylobacter jejuni).