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Battery-free sensing is an architecture for sensing devices in which measurement, computation, and communication are performed without an onboard electrochemical battery as the primary energy reservoir, the required electrical power being instead drawn from the surrounding environment or supplied by an external interrogator ^[1]. The device harvests ambient energy—such as radio-frequency radiation, light, thermal gradients, or mechanical vibration—or receives radio-frequency power radiated by a reader, and uses this energy to operate a sensor, digitize a measurement, and transmit the result, commonly through backscatter modulation of an incident carrier wave rather than by generating a dedicated radio signal ^[2]. Because the node must function under severely constrained and often intermittent power budgets, battery-free sensing devices are characterized by ultra-low-power electronics, energy-neutral operation, and reliance on the same radio channel that delivers power to also carry the sensed data back to the interrogator ^[1]. It is distinguished from conventional battery-powered sensing by the absence of a replaceable chemical energy source and by the tight coupling between energy harvesting and communication, in which the act of sensing and transmitting must be sustained by the instantaneous available energy ^[2]. Such systems typically exploit passive or semi-passive RFID-like principles and are defined by their self-sufficiency and removal of battery-replacement maintenance ^[3].