Electron Beam‐Induced Bulk Modification of Silicone Rubber for Spheroid Formation Devices

ABSTRACT Silicone rubbers have been widely employed in advanced polymeric materials and lab‐on‐a‐chip devices owing to their ease of fabrication, biocompatibility, transparency, and oxygen permeability. However, their practicality is often limited by deformability, surface tackiness, drug sorption, and leaching of low‐molecular‐weight siloxanes, which raises cytocompatibility concerns. Here, we present a systematic study on the bulk modification of silicone rubber via electron beam (EB) irradiation at practically relevant doses (100–1000 kGy). EB irradiation increased the compressive modulus, slightly enhanced hydrophilicity, and significantly reduced surface tackiness, while maintaining high oxygen permeability and optical transparency. The process also markedly reduced low‐molecular‐weight cyclic siloxanes, including D4, a compound known for cytotoxicity. Correlation analysis indicated that the reduction in tackiness strongly corresponded with the decrease in low‐molecular‐weight siloxane content. Although drug sorption remained unchanged, likely due to the intrinsic porosity of silicone rubber, these results demonstrate that EB irradiation is a practical bulk modification strategy that enhances mechanical robustness and cytocompatibility while preserving key physicochemical properties. The process is suitable for batch‐scale industrial manufacturing. Furthermore, an EB‐modified spheroid formation device was fabricated to demonstrate its functional utility, enabling the high‐throughput generation of human induced pluripotent stem cell (iPSC) aggregates while alleviating hypoxic conditions.