Enhanced wide-range monotonic piezoresistivity, reliability of Ketjenblack/deproteinized natural rubber nanocomposite, and its biomedical application

Piezoresistive behavior of 6 to 9 wt % Ketjenblack-reinforced deproteinized natural rubber (KB/DPNR) nanocomposite developed by two-roll mill was studied under compressive pressure (0 to 12.54 MPa). The 6 wt % KB/DPNR exhibited monotonic piezoresistivity, the highest electrical resistance change (485%), remarkable reversibility and minimal hysteresis. Furthermore, a good sensitivity (S) = 1.1 MPa⁻¹ for 0.25 to 2.49 MPa, high test–retest reliability (intraclass correlation co-efficient, ICC = 0.99) under 0 to 2.49 MPa for three repetitions conducted at an interval of 24 h and excellent repeatability (standard deviation, SD = 4.8%) to a swing of 6.25 MPa for 50 cyclic compression were achieved. Homogeneous dispersion and high aspect ratio of KB and higher chemical linkage (due to double crosslinking agents) between KB and DPNR may be responsible for the enhanced piezoresistivity. For practical application, the KB/DPNR was interfaced with the microcontroller through a bridge rectifier via custom-built Simulink and successfully monitored finger pressure in real time during bone movement on human.