Amorphous silicon temperature sensors integrated with thin film heaters for thermal treatments of biomolecules

This work combines a lab-on-chip device with an electronic system for the achievement of a small-scale and low-cost thermal treatment of biomolecules. The lab-on-chip is a 1.2 mm-thick glass substrate hosting thin film resistor acting as heater and, on the other glass side, amorphous silicon diodes acting as temperature sensors. The electronic system controls the lab-on-chip temperature through a Proportional-Integral-Derivative algorithm. In particular, an electronic board infers the temperature measuring the voltage across the amorphous silicon diodes, which are biased with a constant forward current of 50 nA, and drives the heater to achieve the set-point temperature. The characterization of the whole system has been carried out implementing the thermal cycles necessary in the polymerase chain reaction technique for amplification of DNA. To this purpose, the lab-on-chip has been thermally coupled with another glass hosting a microfluidic network made in polydimethilsiloxane, and the time evolution of temperature has been carefully monitored. The measured performances in terms of heating rate, cooling rate and settling time demonstrate that the proposed system completely fulfills the requirements of the investigated biological application.