We herein describe the fabrication, optimisation and characterisation of a biohybrid variable stiffness actuator that creates its own bone. By combining the electroresponsive properties of polypyrrole (PPy) with the compliant response of alginate gels functionalised with cell-derived plasma membrane nanofragments (PMNFs) it was possible to obtain bio-induced variable stiffness actuators. When the PMNFs were incubated into MEM, i.e. exposure to Ca, this caused the formation of calcium-phosphate minerals (i.e. amorphous calcium phosphate and hydroxyapatite) in the alginate gel, resulting in a more rigid layer and thus reducing and finally impeding the movement of the actuator, locking it in a fixed position within only 2 days. These actuators could morph in various, pre-programmed shapes and change their properties from soft to rigid. Adding different patterns to the actuator allowed locking the device in a predetermined shape without energy consumption, facilitating its application as soft-to-hard robotics as a biohybrid variant of so-called 4D manufacturing. The devices could wrap around and integrate into bone by the induced mineralisation in and on the gel layer. This illustrates its use as a potential tool to repair bone or in bone tissue engineering.