Quantifying Heat Transfer in DMD-based Optoelectronic Tweezers with Infrared Thermography

摘要

Optoelectronic tweezers (OET) have emerged in recent years as a powerful form of optically-induced dielectrophoresis for addressing single cells and trapping individual nanostructures with DMD-based virtual-electrodes. In this technique an alternating electric field is used to induce a dipole within structures of interest while very low-intensity optical images are used to produce local electric field gradients that create dynamic trapping potentials. Addressing living cells, particularly for heat-sensitive cell lines, with OET's optical virtual-electrodes requires an in-depth understanding of heating profiles within OET devices. In this work we present quantitative measurements of the thermal characteristics of single-crystalline-silicon phototransistor based optoelectronic tweezers (PhOET). Midwave infrared (3 - 5 micron) thermographic imaging is used to determine relative heating in PhOET devices both with and without DMD-based optical actuation. Temperature increases of approximately 2°C from electrolyte Joule-heating are observable in the absence of DMD-illumination when glass is used as a support for PhOET devices. An additional temperature increase of no more than 0.2°C is observed when DMD-illumination is used. Furthermore, significantly reduced heating can be achieved when devices are fabricated in direct contact with a metallic heat-sink.