Inkjet-Printed Titanium Carbide Nanoparticle-Based Flexible Bidirectional Flow Sensors for Flow-Aware Autonomous Systems

This study developed a cleanroom-free fabrication approach for flexible cilia-inspired flow sensors using inkjet-printed titanium carbide nanoparticle strain gauges on heat-stabilized polyester cantilevers. The authors optimized TiC ink formulation for conductivity, viscosity, surface tension, wettability, and long-term colloidal stability, then fabricated printed piezoresistive sensors that responded to cantilever bending through conductive domain discontinuity and geometric strain effects in the nanoparticle percolation network. The devices showed repeatable electromechanical behavior, a linear response to dynamic and quasi-static tip displacement over part of the operating range, quadratic response to low-velocity water and air flow, and saturation at higher flow velocities consistent with finite-element fluid-structure interaction simulations. The sensors also demonstrated bidirectional sensing by producing opposite resistance changes under forward versus reverse airflow. As a system-level validation, two identical sensors were mounted on an omnidirectional Nexus mobile robot and used for local airflow-based source seeking, enabling wind-direction-aware autonomous navigation toward a fan without global position information. The work highlights inkjet printing as a scalable route for flexible printed sensing structures for robotics and autonomous systems.