Biological tissues are complex structures with changing mechanical properties depending on physiological or pathological factors. Thus they are extendible under normal conditions or stiff if they are subject to an inflammatory reaction. We design and fabricate a lowpower and low-cost stiffness-variable tissue phantom (SVTP) that can extend up to 250% and contract up to 5.4% at 5 V (1.4 W), mimicking properties of biological tissues. We investigated the mechanical characteristics of SVTP in simulation and experiment. We also demonstrate its potential by building an oesophagus phantom for testing appropriate force controls in a robotic implant that is meant to manipulate biological oesophageal tissues with changing stiffness in vivo. The entire platform permits efficient testing of robotic implants in the context of anomalies such as long gap esophageal atresia, and could potentially serve as a replacement for live animal tissues. A. Thorn and D. Afacan-Contributed equally.