Optically Actuated soft Microrobot Family for Single-cell Manipulation.

Precisely controlled manipulation of non-adherent single cells is often a pre-requisite for their detailed investigation. Optical trapping provides a versatile means for positioning cells with sub-micrometer precision or measuring forces with femto-Newton resolution. A variant of the technique, called indirect optical trapping, enables single-cell manipulation with no photodamage and superior spatial control and stability by relying on optically trapped microtools biochemically bound to the cell. High-resolution 3D lithography enables us to prepare such cell manipulators with any pre-defined shape, greatly extending the number of achievable manipulation tasks. Here, we present for the first time a novel family of cell manipulators that are deformable by optical tweezers and rely on their elasticity to hold cells. This provides a more straightforward approach to indirect optical trapping by avoiding biochemical functionalization for cell attachment, and consequently by enabling the manipulated cells to be released at any time. Using the photoresist Ormocomp, we characterize the deformations achievable with optical forces in the tens of pN range and present three modes of single-cell manipulation as examples to showcase the possible applications such soft microrobotic tools can offer. The applications described here include cell collection, 3D cell imaging and spatially and temporally controlled cell-cell interaction. This article is protected by copyright. All rights reserved.