We constantly seek ways to achieve the highest usable output with the lowest power consumption. No matter how far engineers and scientists push the limits of knowledge chasing optimal net ROE (return on energy), there will always be room for improvement. Space travel, heating cities, and manufacturing require extremely large power sources, but wearables live at the opposite end of the power spectrum, often at near-nanowatt levels. We’ve written about low power applications such as Nanyang Technological University’s multipurpose smart chip for implants and Ambiq Micro’s Apollo2 processor that uses minimal energy when operating and even less on standby.
Engineers at Cambridge University recently published a study in Science that explains how they used inkjet printing to fabricate an ultra-low power organic transistor with high signal gain. The Cambridge transistor uses one thousand times less power than silicon or metal oxides with a signal-to-noise ratio that’s one hundred times better.
The transistor uses less than one nanowatt of power to amplify close to the theoretical thermionic limit. (This refers to the net remains of a thermally-excited charge emission process when a charge is emitted from one solid-state region to another.) While you can’t leave behind more energy that you used when changing from one state to another, getting close to parity — aka the thermionic limit — is a breakthrough. The essential point is the Cambridge researchers have moved the energy efficiency puck further down the ice.
The engineers state the organic transistor demonstrates reliable performance for months with no degradation. Potential applications include pairing the transistor with wearable devices to detect weak electrophysiological signals from the skin. One example includes tracking eye movement with electro-oculography. As the search for energy efficiency grail continues, medical and wellness wearables will hopefully be able to take advantage of the benefits realizable from steps along the way.