Many sensors stop when batteries run out. These sensors get power from sunlight, heat, or movement and keep running for years without help.
Many sensor applications today face a common challenge which is powering devices in environments where battery replacement is difficult, costly, or impractical. Researchers from the University of Arkansas and the University of Michigan are tackling this by developing ultra-low-power, self-powered temperature sensors that harvest energy directly from the environment.
The new sensors use graphene-based solar cells to draw energy from sunlight and other environmental sources, eliminating the need for conventional batteries. They consume power at the nanowatt level, a billion times less than standard sensors, and can operate autonomously for decades. This “set it and forget it” design could dramatically reduce maintenance costs while supporting large-scale Internet of Things deployments.
The sensors are designed to be multimodal, capable of supplementing solar energy with thermal, kinetic, acoustic, or ambient radiation when sunlight is insufficient. This flexibility makes them suitable for applications where access is limited or frequent servicing is impractical, such as monitoring livestock, climate conditions in agriculture, or building security systems.
To achieve this, the researchers removed the conventional power management unit and connected three sets of graphene solar cells directly to storage capacitors. These capacitors provide the voltage needed to run the sensor, allowing it to operate for over 24 hours after only a few minutes of charging. This approach reduces power consumption and extends the device’s operational lifetime without relying on rechargeable batteries.
The development process involved fabricating multiple graphene solar cells, assembling them with wire bonding, and testing their performance under light exposure. Cells were connected in series to boost output voltage, ensuring the sensor has sufficient energy even in variable conditions.
The next step in the research is integrating a kinetic energy harvester to capture vibrations in addition to solar energy. This will create a fully multimodal system capable of drawing power from multiple environmental sources, further increasing reliability and autonomy.
