Institute of Fundamental Technological Research

The advancement of force microsensors has shifted towards alternative fabrication methods offering enhanced flexibility, cost efficiency, and adaptability. Traditional silicon-based sensors face limitations such as mechanical fragility, thermal expansion mismatches, and high fabrication costs, necessitating alternative approaches. This study explores a bottom-up fabrication approach using electro-galvanic deposition to develop nickel-based capacitive force microsensors. Unlike conventional methods, electro-galvanic deposition enables precise control over material thickness and microstructure, allowing for the fabrication of robust, metal-based sensors with superior toughness and mechanical reliability. Nickel, chosen for its high tensile strength, corrosion resistance, and adaptability to high temperatures, is well-suited for demanding applications. The fabrication process involves UV maskless lithography for mold patterning, followed by electro-galvanic deposition in a modified Watt's bath with saccharin additives to control grain structure. This enables fine-tuning of nickel's mechanical properties, enhancing hardness and ductility. The capacitive comb sensor structure, integrated with a high-resolution capacitance-to-digital converter, enables precise force measurements with a linear response and high sensitivity. Experimental validation included mechanical testing, calibration, and stability analysis under controlled loading conditions. Results confirmed a strong linear force-capacitance relationship (R2 = 0.9898) and excellent long-term stability, with minimal capacitance drift under sustained load.

Nickel-based sensor, Bottom-up process for sensor fabrication, Electro-galvanic deposition, Capacitance stability, Silicon sensor limitations, Industrial sensor applications, Sensor durability, Displacement-force calibration