Reconfigurable Temperature Control at the Microscale by Light Shaping

Abstract

From physics to biology, temperature is often a critical factor. Most existing techniques (e.g., ovens, incubators, ...) only provide global temperature control and incur strong inertia. Thermoplasmonic heating is drawing increasing interest by giving access to fast, local, and contactless optical temperature control. However, tailoring temperature at the microscale is not straightforward since heat diffusion alters temperature patterns. In this article, we propose and demonstrate an accurate and reconfigurable microscale temperature shaping technique by precisely tailoring the illumination intensity that is sent on a homogeneous array of absorbing plasmonic nanoparticles. The method consists in (i) calculating a Heat Source Density (HSD) map, which precompensates heat diffusion, and (ii) using a wavefront engineering technique to shape the illumination and reproduce this HSD in the nanoparticle plane. After heat diffusion, the tailored heat source distribution produces the desired microscale temperature pattern under a microscope. The method is validated using wavefront-sensing-based temperature imaging microscopy. Fast (sub-s), accurate, and reconfigurable temperature patterns are demonstrated over arbitrarily shaped regions. In the context of cell biology, we finally propose a methodology combining fluorescence imaging with reconfigurable temperature shaping to thermally target a given population of cells or organelles of interest, opening new strategies to locally study their response to thermal activation