Dr. Alex Thompson, Imperial College Research Fellow, Surgical Innovation Centre, St. Mary's Hospital, Department of Medicine, Imperial College London, UK

Speech Title: A three-dimensional microscale gripper with an integrated optical force sensor for controlled micromanipulation

Abstract: Microrobotic devices have wide-ranging potential applications in biology and medicine, including targeted drug delivery, cellular manipulation and microsurgery. With the aim of developing microscale surgical robots, we have fabricated a tethered 3D microgripper with integrated force sensing on the tip of an optical fibre using two-photon polymerisation. The device measures approximately 100 µm in each dimension and allows manipulation of cellular scale objects (i.e. tens of microns) via a passive, compliant actuation mechanism. To provide precise control over manipulation tasks, an optical force sensor is incorporated into the gripper. The sensing mechanism is based on thin film interference: the spacing between thin plates in the centre of the gripper varies under compression, effecting interferometric changes in the light reflected by the sensor. Broadband light from a supercontinuum laser source is coupled into the optical fibre on which the microgripper is mounted in order to address the sensor, and the light reflected by the sensor is collected by the fibre and directed onto a spectrometer for detection. Machine learning algorithms are used to convert the measured spectra into force readings such that the axial force exerted by/on the gripper can be calculated in real time with an accuracy of below 1 µN. In this talk, I describe the design, characterisation and testing of the microgripper – with a focus on the optical force sensing mechanism – and demonstrate its capability for micromanipulation with real-time force feedback.

Keywords: microrobot, microgripper, optical force sensing, optical interferometry, spectroscopy, two photon polymerisation, biophotonics