- Penn State researchers built a monolithic 3D chip that runs entirely on ambient light without tapping a battery
- The chip stacks silicon photovoltaic sensors, complementary MoS₂/WSe₂ logic, and graphene chemical sensors about 50 nm apart.
- The development also opens the door to larger 2D circuits incorporating some of the same design philosophy in the future.
Research at Penn State University has resulted in an interesting engineering breakthrough: the construction of a compact integrated circuit that runs entirely on solar energy.
The IC, which omits batteries entirely, aims to perform calculations and be able to detect chemicals in its vicinity by harvesting available solar energy and aims to do so by stacking everything monolithically rather than splitting it into different arrays.
The move comes as engineers continue to grapple with the need for versatile and durable IoT and edge computing systems, many of which are deployed in remote or hard-to-reach locations, making changing batteries a difficult, if not impossible, proposition at times.
A vertically stacked solution focused on solar energy
Battery-free electronic devices that rely on renewable energy are receiving increased attention as engineers, stakeholders and consumers look for such devices to meet growing market demand.
What makes Penn State’s development research team so unique is that it has attempted to address what conventional electronics has failed to do so far: reducing losses by investing in a structure that effectively bypasses a significant portion of the board area requirements, wiring losses in terms of power and latency that are at stake for such devices.
The chip does this by taking advantage of two types of semiconductor materials (MoS₂ and WSe₂), a silicon photovoltaic module and graphene-based sensors, and stacking the three layers vertically.
The graphene-based sensors on top respond to liquids placed on them, sending electrical signals that are processed in the intermediate logic layer, where the semiconductor layer is located, while the silicon photovoltaic module on the bottom generates power by converting ambient light into electricity.
“We have shown that heterogeneous materials (silicon, graphene, MoS)2 and WSe2—Can be monolithically integrated in three dimensions to create a self-powered sensing and computing system. This is different than simply placing separate chips next to each other or connecting them externally. “We show that sensing, computing, and energy harvesting can be brought closer to the nanoscale, 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 environments where batteries could be difficult to replace, even as efficiency takes center stage in lower-power nanoscale circuits.
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