Extract Non-Thermal Fluctuations from an Experimentally Measured Histogram of a Confined Active Brownian Particle

Active Brownian particles (ABPs), colloidal particles driven into persistent motions by external fields, can serve as a model for understanding the non-thermal behavior of biological systems. Non-thermal fluctuations of an ABP are expected to behave differently from thermal Brownian motions in distinctive manners, e.g., exhibiting different diffusivities, effective temperatures, and fluctuation power spectral densities. While the non-thermal fluctuations can be separated from the thermal ones in their power spectral densities, it is non-trivial to decouple the non-thermal from thermal changes in a fluctuation histogram, because the experimentally measured fluctuation histogram is a convolution of the two fluctuations. We hypothesize that the non-thermal fluctuation could be extracted from the overall noise histogram by standard deconvolution algorisms when thermal fluctuations can be determined independently. This presentation reports an experimental study using a model ABP in a quadratic potential well to test the hypothesis and its limitations.