Design and experimental characterization of thin film heaters on glass substrate for Lab-on-Chip applications

Abstract

This paper presents a comprehensive procedure for the design and implementation of thin film heaters manufactured on glass substrates. The thermal and electrical behavior of the heaters have first been simulated and proper design solutions have been adopted for increasing the thermal resistance of the heaters, thus decreasing their power consumption. Trenches were adopted in order to thermally isolate the heater from the glass substrate. The presence of four different layouts of trenches on the back and the front side of the glass slide with different geometries was extensively simulated. The simulated geometries were manufactured and an automatic sawing machine was exploited to dig 240μm wide trenches in the glass substrate. The trenches were typically stopped at about 80μm from the opposite surface. Techniques commonly adopted for measuring the temperature coefficient of resistance, the thermal resistance and thermal capacitance in the case of Si-based microheaters have conveniently been modified to take into account the fundamentally different thermal parameters of a heater manufactured on glass. An experimental improvement of the thermal resistance up to 217% on a heat sink and 30% in air has been obtained when a large part of the thermal mass under the microheater was removed. The thermal capacitance was also considerably decreased, thus improving the dynamic thermal behavior.