Seal whisker-inspired fully printed MEMS flow sensor via micron-scale soft material additive manufacturing

Seals are renowned for their exceptional ability to hunt, a capability attributed to the uniquely evolved whisker morphology that suppresses vortex-induced vibrations and enables them to track hydrodynamic trails in the water. In this study, we present the first direct experimental comparison of replicated whisker geometries from harbor seals, gray seals, and sea lions, integrated into an artificial follicle-sinus complex flow sensor. A custom-formulated elastic resin was developed to address the limitations of current photocurable soft materials, enabling the fabrication of mechanically compliant structures with high spatial fidelity. All components, including biologically accurate whisker geometries and a soft, cavity-integrated FSC, were fabricated using projection micro-stereolithography, achieving sub-10 μm resolution in a single-step process. Piezoresistive sensing was achieved via capillary infusion of graphene nanoplatelet (GNP) ink into the 500 µm embedded channels with 20 µm corrugated layers within the FSC base. Static and dynamic characterization confirmed high strain sensitivity (GF = 16.57 in tension, 10.67 in compression) and stable performance over 3000 cycles, demonstrating suitability for both steady-state flow sensing and vortex characterization measurements. Comparative flow experiments further revealed that phocid seal whiskers (harbor and gray seals) suppress vortex-induced vibrations and provide superior signal-to-noise ratios compared to sea lion whiskers. This work lays the foundation for high-resolution, species-specific sensing technologies that can advance both biological understanding and engineered flow navigation systems.