Like photosynthesis in plants: This CPU uses solar power to ‘run computations’ without the need for batteries Rahimnoorali11@gmail.com (Rahim Amir) | usagoldmines.com

• Penn State researchers built a monolithic 3D chip that runs entirely off ambient light without leveraging a battery
• The chip stacks silicon photovoltaics, MoS₂/WSe₂ complementary logic, and graphene chemical sensors within ~50 nm of each other
• The development also opens the door for larger 2D circuits that incorporate some of the same design philosophy in the future

Research at Penn State university has come up with an interesting breakthrough in engineering, building out a compact integrated circuit that runs entirely off solar power.

The IC, which skips batteries altogether aims to run calculations and be able to sense chemicals in its vicinity by harvesting solar power available to it aims to do so by stacking everything monolithically versus splitting things up across different dies.

The move comes as engineers continue to grapple with the need for long-lasting and versatile IoT and edge computing systems, many of which are deployed in remote or hard to access locations, making changing batteries a hard, if not impossible proposition at times.

A vertically-stacked solution that centers around solar

Battery-free electronics that rely on renewable power are in greater focus as engineers, stakeholders, and consumers seek such devices to meet growing market demand.

What makes the research team at Penn State’s development so unique is that it has attempted to address what conventional electronics have failed to do so far: cutting losses by investing in a structure that effectively skips a significant part of the board area requirements, wiring losses in terms of power and latency that are in play for such devices.

The chip does so by leveraging two types of semiconducting materials (MoS₂ and WSe₂), a silicon photovoltaic module, and graphene-based sensors, and stacking all three layers vertically.

The graphene-based sensors at the top respond to liquids placed on them, sending electrical signals that are processed in the middle logic layer, where the semiconductor layer lies, while the silicon photovoltaic module at the bottom generates power by converting ambient light into electricity.

“We showed that heterogeneous materials—silicon, graphene, MoS₂ and WSe₂—can be integrated monolithically in three dimensions to create a self-powered sensing and computing system. This is different from simply placing separate chips next to each other or connecting them externally. We show that sensing, computation, and energy harvesting can be brought into nanoscale proximity, which can reduce footprint, interconnect length, and energy loss,” said Saptarshi Das, one of the authors of the paper documenting this approach.

While the move itself documents a small purpose-built chip, it has interesting ramifications for the future, where larger circuits could use the design as a building block for IoT needs, especially in remote settings where batteries might be difficult to replace even as efficiency takes center stage for lower-powered, nanoscale circuits.