Multichannel soft microfluidic force sensors: design, characterization, and application in laparoscopy

This work presents the design, fabrication, and characterization of multichannel soft microfluidic force sensors for integration with laparoscopic graspers. The sensors consist of PDMS structures encapsulating Galinstan-filled microchannels, where applied forces induce structural deformation and a corresponding increase in electrical resistance. Fabrication is achieved through 3D printing and PDMS molding under cleanroom-free conditions, enabling cost-effective and reproducible sensor production. We systematically investigated key design parameters, including microchannel geometry and sensor thickness and stiffness, through finite element simulations and experimental validation. Results show that thinner, softer sensors with inverted stepped-triangle microchannels exhibit the highest sensitivity. To further extend functionality, we developed both multilayer and coplanar multichannel sensor designs, enabling dual-range sensing with improved linearity and tunability. The sensors were integrated into a laparoscopic grasper, with one sensor mounted on the handle to measure thumb-applied actuation forces and another sensor on the jaw to capture tissue contact forces. This dual-sensing configuration highlights the potential of soft microfluidic sensors to restore tactile feedback in minimally invasive surgery. Overall, microfluidic technology provides a practical, scalable approach to soft-sensing systems for surgical tools, robotics, and human-machine interfaces.