- Penn State researchers built a monolithic 3D chip that runs entirely on ambient light without using a battery
- The chip stacks silicon photovoltaic sensors, complementary MoS₂/WSe₂ logic, and graphene chemical sensors approximately 50 nm from each other.
- 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 exciting engineering breakthrough, creating a compact integrated circuit that runs entirely on solar power.
The integrated circuit, which completely ignores batteries, aims to run calculations and detect nearby chemicals by harvesting the solar energy available to it. It aims to do this by stacking everything monolithicly rather than spreading them across different chips.
The move comes as engineers continue to grapple with the need for durable, versatile IoT and edge computing systems, many of which are deployed in remote or hard-to-reach locations, making battery changing sometimes difficult or impossible.
A vertically stacked solution focused on solar energy
Battery-free electronic devices that rely on renewable energy are receiving greater attention as engineers, stakeholders and consumers seek such devices to meet growing market demand.
What makes the Penn State research team so unique is that it attempted to solve what conventional electronics has so far failed to do: reduce losses by investing in a structure that effectively ignores a significant portion of the board area requirements, power and latency wiring losses that are at play for such devices.
To do this, the chip uses two types of semiconductor materials (MoS₂ and WSe₂), a silicon photovoltaic module and graphene-based sensors, and stacks the three layers vertically.
The graphene-based sensors at the top react to liquids placed on them, sending electrical signals that are processed in the central logic layer, where the semiconductor layer is located, while the silicon photovoltaic module at the bottom generates energy by converting ambient light into electricity.
“We have shown that heterogeneous materials: silicon, graphene, MoS2 and WSe2– can be monolithicly integrated 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, calculation and energy harvesting can be brought together at the nanoscale, which can reduce the footprint, interconnect length and energy loss,” said Saptarshi Das, one of the authors of the paper documenting this approach.
While this 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, particularly in remote environments where batteries might be difficult to replace, although efficiency takes center stage for low-power nanoscale circuits.
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