A robust fluidic strain sensor based on a biocompatible conductive poly(3,4-ethylenedioxythiophene) polystyrene sulfonate multiwall carbon nanotube (PEDOT:PSS/MWCNT) liquid is proposed. A simple fabrication process is followed by the 3D printing of a 2.5 cycle sinusoidal channel, and the infiltration liquid is infilled using custom-made automated pumping syringes. The sensor showed a highly linear response (R2 = 0.9935), a minimal hysteresis (1.56%), a gauge factor (GF) of 89.4, and a two-order change in resistance up to 150% strain. The device was tested for 1000 cycles at 30% strain and showed the ability to follow the applied strain up to a maximum frequency of 10 Hz. Moreover, the device showed a significantly stable response under the full humidity range (0–100% RH) and at temperatures from 20 to 40 ℃. As a proof-of-concept demonstration, the fabricated sensor was used with a robotic leg as a high-end feedback sensor. Furthermore, the biocompatibility of the device was confirmed before its applications in wearable electronics by the cell viability assessment of human epidermal keratinocytes (HEKp) and human umbilical cord vascular endothelial cells (HUVEC). The simple fabrication process and ultrahigh sensitivity of the device make it a robust candidate for wearable and robotic applications.