Controllable synthesis of nickel nanowires and its application in high sensitivity, stretchable strain sensor for body motion sensing

A facile, low-cost magnetic field-assisted chemical reduction method was proposed for synthesizing nickel nanowires (NiNWs) with both controllable diameter and high length to diameter (L/D) ratio at temperature as low as 60 degrees C. NiNWs with diameter as low as 180 +/- 21 nm and L/D ratio as high as 300 were achieved by controlling the reaction temperature, NiCl2 concentration and the quantity of reductant in a magnetic field of 170 mT. Based on the NiNWs, a high-sensitivity and stretchable strain sensor with sandwich structure consisting of NiNWs and Ecoflex elastomer was proposed. Gauge factor as high as 200 was demonstrated up to a strain of 100%. Applications of the sensor in detecting body motion including finger gestures, facial expressions and different phonations are presented. This study provides a promising solution for smart sensors for next generation robotics as well as for human-machine interfacing applications.