Silicon-based microneedle array electrodes for biopotential measurement

Biopotential signals in shin tissue reflect the body's healthy conditions. So the measurement of these signals can diagnose whether the body has diseases or not. Traditional technology used to measure these signals results in pain, bleeding, infection, etc. Recently, the microneedle electrodes are used to measure these signals owing to their advantages, such as painless, low cost, easily made, etc. This paper presents a new method to fabricate the silicon-based microneedle array electrodes intended for measuring biopotential signals in the skin tissue. The arrays consist of a 5 mm x 5 mm silicon base with gold film, and 49 silicon needle-type electrodes with gold film in a 7 x 7 array on the silicon base. Each needle is approximately 700 mu m long, 70 mu m in diameter at the base. The 1 mm-thick silicon wafer is cut to form 300 x 300 x 700 pm rectangular micro-column by dicing saw. Then the 5 mm x 5 mm silicon base with these columns is cut off to form the whole substrate. The rectangular micro-columns are etched in the mixture acid solution (HNO3 and HF) until getting sharp microneedles. Then the surface of the microneedles is sputtered the gold film, the microneedle electrodes are formed. One array of these electrodes exhibits low impedance for measuring biopotential signals.