Fabrication of magnetically actuated micropillars combining micromolding and C,H insertion crosslinking

In recent years, poly(dimethylsiloxane)-based microelectronical mechanical systems actuators using magnetic actuation have been reported to enable active stimulation of the cells. However, poly(dimethylsiloxane) is chemically inactive and thus, chemical modification of the posts is difficult and relies on a non-permanent physical modification for cell adhesion and repellency. Here, a simple process to fabricate a new tool for cellular mechanobiology is presented. This work aims to develop a novel method to fabricate polymeric micro-actuators with a medium to high deflection in aqueous media and a possibility to further modify their surface chemistry. A new approach is reported to create magnetic micropillars utilizing a hydrogel copolymer with photochemical moieties relying on C,H insertion crosslinking (CHic). The setup consists of poly(N,N-dimethylacryl amide) (PDMAA) microstructure arrays filled with magnetic iron oxide (II, III) nanoparticles. With the help of a rotating permanent magnet or an electromagnet, deflection of the pillars can be observed under low magnetic fields and can be controlled through either the magnetic field or the swelling of the polyelectrolyte structures. The actuation behavior of the magnetic microstructures is investigated in different media and the results show that the microstructured P(DMAA) arrays are good candidates for the actuation in aqueous solutions, ranging from ethanol to PBS. SaOs-2 bone cancer cells are used for cell experiments to investigate the biological compatibility of the microstructures, and their behavior on the magnetic microstructures.