Building a Custom Microscope to Study Brownian Motion and Active Matter

Our goal is to build an optical microscope, calibrate it, and make precise measurements of Brownian motion and diffusion using multiple approaches such as mean squared displacement (MSD) analysis and differential dynamic microscopy (DDM). These methods of analysis were applied to quantify the motility of active matter and standardize the process to develop an advanced module for the graduate program. We constructed a microscope based on the design by Kemp et al.(arXiv:1606.03052). Then, the Brownian motion of 1 micron colloidal particles were studied and both single particle tracking and image correlation techniques were implemented to analyze colloidal diffusion. To do this, publicly available matlab codes for particle tracking, MSD analysis, and DDM analysis were applied to calculate the diffusion coefficient. These methods were utilized to quantify the diffusion of two different types of active matter: janus particles and swimming microorganisms. This was done to quantify the motility of active matter. This project is being developed into an advanced lab module to be an introduction to physics research, fortify concepts from optics and statistical physics, and give students experience in building optical systems and analyzing noisy data.