A Femtosecond Laser Micromachining for Drilling PDMS Membranes in Organ-on-a-Chip Applications

Organ-on-a-chip (OoC) technology seeks to replicate the functions of human organs and tissues. This study investigates a flexible microfabrication method based on femtosecond laser micromachining (FLM) as an alternative for producing membranes of controlled porosity for OoCs. Polydimethylsiloxane (PDMS) membranes with various thicknesses were microdrilled. The influence of laser parameters such as pulse energy and exposure time on microhole geometry was evaluated. Pulse energy was found to significantly affect hole diameter, whereas exposure time played a comparatively minor role. Increasing pulse energy or number of pulses always led to greater microhole taper angles. Prediction models based on experimental data were developed for setting up operating parameters the laser-based ablation process. To provide a more in-depth understanding of the physics underlying the PDMS ablation, a numerical model incorporating plasma shielding effects and energy-dependent material removal was developed. Membrane biocompatibility was assessed by seeding human mesenchymal stem cells on them after assembling into an OoC device. Strong cell adhesion and the rapid formation of a homogeneous cell monolayer across all types of microdrilled membranes confirmed their suitability for bioengineering applications. Overall, FLM offers a flexible and precise approach to microdrilling PDMS membranes, highlighting its potential for integration into the fabrication of OoC platforms.