Optical force sensing with cylindrical microcontainers

Oliver N., Denz C., Meißner R.

Abstract

Quantitative force sensing reveals essential information for the study ofbiological systems. Forces on molecules, cells, and tissues uncover functioningconditions and pathways. To analyze such forces, spherical particles aretrapped and controlled inside an optical tweezers (OT) trap. Although thesespherical particles are well-established sensors in biophysics, elongatedprobes are envisioned for remote force sensing reducing heat damage causedby OT. There is thus a growing demand for force metrology with OT usingcomplexly shaped objects, e.g., sac-like organelles or rod-like bacteria. Here,the employment of Zeolite-L crystals as cylindrical force sensing probes insidea single optical trap is investigated. It is shown that cylindrical objects can beused as force probes since existing calibration assays can be performed withsuitable corrections. Forces of active driving assays are compared with passivecalibration methods. Finally, the investigations are extended to direct forcemeasurements based on momentum calibration, in which the influence ofrotation due to torque in a single optical trap is unveiled. Simulations revealthe relation between torque and the position of equilibrium in the trap. Theresults highlight the functionality of Zeolite-L crystals as probes for forcesensing, while opening perspectives for enhanced, accurate force metrology inbiophotonics.