A Gym for Cells—Direct Laser Writing of Magnetic Multilayered Micro Actuators for Mechanical Stimulation of Cells

Abstract Mechanical forces play a crucial role in many biological processes, including cell–cell and cell–matrix interactions. The generation of surface‐attached multilayer micromagnet systems fabricated by two‐photon lithography and the use of such systems to perform single‐cell actuation are presented. The actuators are generated by two‐photon crosslinking and consist of a soft and flexible surface‐attached hydrogel layer swollen in aqueous medium and a hydrophobic polymer filled with magnetic nanoparticles. To this, thin copolymer bilayers containing a photoreactive crosslinking moiety are deposited on a solid substrate. The crosslinker units are activated by two‐photon excitation and react via a C,H insertion reaction with any nearby aliphatic C,H bonds. This leads to crosslinking and surface‐attachment of the forming structures so that arrays of micromagnetic pillars with spatially controlled cell adhesion behavior are formed in a single step. Cells are placed on the pillars and actuation is induced by an external magnetic field allowing for highly controllable dynamic and static actuation. Geometric differences can be used to vary cell morphogenesis and movement of the actuators to stretch the cells resulting in highly customizable actuator systems for specific cell growth and actuation control and the study of cell behavior on the molecular level.