Optical torque wrench

The optical torque wrench setup extends standard Optical Tweezers to torque manipulation and detection. A birefringent particle is optically trapped and torque can be applied and measured using the polarization of the trapping laser.

Schematic OTW setup

We fabricate the microscopic birefringent crystals by Laser Interference Lithography (LIL), an inexpensive technique which simplifies greatly the protocol.

Torque can be measured dynamically on a trapped crystal, demonstrating the excitability of the system.