Built from flexible, compliant materials, soft robots are gaining relevance for tasks ranging from minimally invasive surgery to deep-sea exploration but remain held back by a fundamental constraint. To sense their surroundings and react, most soft robots rely on separate electronic sensors, signal-processing circuits and powered actuators, all coordinated by computers. This chain of components adds weight, complexity and points of failure, particularly in wet, hot or high-pressure settings where electronics are highly susceptible to disruption.