This test is one of the first attempts to create autonomous sensor systems capable of harnessing energy from various environmental sources - including solar, thermal, acoustic, kinetic, nonlinear, and ambient radiation.
The ultimate objective is to develop multimodal sensors (which integrate multiple power sources mentioned above) that use the energy-harvesting properties of graphene, ensuring longevity of several decades and facilitating the realization of the "Internet of Things," where intelligent technology is seamlessly integrated into everyday life.
The success of the sensor depended on overcoming two challenges: minimizing the power consumption of sensors to nanowatts (one billionth of a watt), which is significantly lower than the existing standard of microwatts (one millionth of a watt), and using energy sourced from the surrounding environment to power the sensor.
Key to the challenge is that this system, along with future iterations, will not use batteries, which have a finite lifespan, enabling graphene-based energy harvesters to maintain extended operational lifetimes, potentially spanning decades.
Power has to be drawn from the local environment, so it's self-powered and autonomous, and it has to have an extremely long operational lifetime to dramatically reduce the total cost of ownership. So set it and forget it.
Paul Thibado, University of Arkansas
The study will assess the feasibility of developing an ultra-low-power temperature sensor that utilizes graphene-based solar energy.
We thought if we could remove the power management unit, maybe this sensor system would take an even smaller amount of power. So that is what we did. Then we connected three sets of solar cells to power the temperature systems directly with three storage capacitors.
Ashaduzzaman, University of Arkansas
Thibado added that “We anticipate building devices that harvest multiple sources of energy within that device.”
By designing them as "multimodal," temporary deficits in solar energy can be supplemented with supplementary thermal or non-linear power sources, depending on the situation.
Thibado envisions the sensors being deployed in sectors and applications where their utility is evident, but the requirement for battery replacements would render them labor-intensive and expensive.
Potential uses might encompass agricultural climate observation, livestock tracking, wearable fitness devices, building security systems, predictive maintenance, and various other fields.
Overview of Work
The initial application outlines the research in straightforward terms, demonstrating how the researchers constructed numerous graphene-based solar cells, connecting them using wire bonding into conventional packages, and analyzing the current-voltage characteristics of each under light exposure.
The solar cells were linked in series to enhance the output voltage.
Three distinct sets of solar cells were employed to charge three storage capacitors to the voltage levels necessary for the temperature sensor.
The storage capacitors require only a few minutes to charge, yet power the sensor system for more than 24 hours without recharging. Using storage capacitors also eliminates the need for a typical power management chip and the commonly used rechargeable battery.
As a result, one can lower the overall power consumed by the sensor system and significantly extend its useful life.
Ashaduzzaman has been engaged in the development of the temperature sensor for approximately a year and a half.
The next step will involve refining a kinetic energy harvester that captures energy from the distinctive vibrational properties of graphene. This functionality will subsequently be integrated with the solar sensor, resulting in a multi-modal sensor.
Journal Reference:
Thompson, A., et al. (2025). Array of mini-graphene-silicon solar cells intermittently recharges storage capacitors powering a temperature sensor. Journal of Vacuum Science and Technology B. DOI: 10.1063/10.0039935.