The system is devoted to intracellular measurements and is fully interactive through the use of a haptic joystick. The force-feedback mechanism allows the user to interactively guide an optically trapped bead and obtain the stiffness matrix of a liquid or biological sample with high spatial resolution (a few nanometres) and an update frequency of 1 kHz.

Using specialized analog hardware along with a dedicated algorithm, the researchers can extract the full 3D stiffness matrix of the optical trap in real time, including the off-diagonal cross-terms. The hardware is also capable of simultaneously recording data for subsequent offline analysis, which allows the team to check that a good correlation exists between the classical analysis of stiffness and the system's real-time measurements.

Instantaneous stiffness measurements are displayed in real time on a graphical user interface. The whole system has been built and is operational. Early results have been reported in Nanotechnology that confirm the consistency of the real-time measurements with offline computations.

This work was financed by GEBERT RüF STIFTUNG.