Photothermal Microscopy and
Spectroscopy Webinar

On a mesoscale, suspensions of locally heated colloidal particles can to some extent be described like ordinary isothermal systems with effective parameters that can be predicted for sufficiently symmetric setups. To a lesser degree, this still holds for asymmetrically heated particles that become “active”, self-propelling microswimmers, due to unbalanced thermal gradients. It is thus not always easy to find informative signatures of the local particle heating and activity, accessible to mesoscale observers. Some paradigmatic situations that we have recently considered in this respect comprise active heat engines, polarization-density patterns spontaneously emerging around activity gradients, ensuing active ratcheting, and time-reversal symmetry breaking fluctuations in non-reciprocal field theories.