Photosynthesis powers microprocessor for six months
Researchers have built an AA-battery-sized device that ran an ARM device for six months, using photosynthesis as a power source.
Professor Christopher Howe and his colleagues at the University of Cambridge's Department of Biochemistry developed a plastic and aluminium enclosure housing an algae called Synechocystis, which they used to generate power for a microprocessor that could be used in IoT applications.
Synechocystis is a type of cyanobacteria, and produces oxygen through photosynthesis when exposed to sunlight.
The researchers tested the device in both a household setting and semi-outdoor conditions with natural light and associated temperature fluctuations.
It was left on a windowsill at Dr. Paolo Bombelli's home and remained there from February to August 2021.
The device generated a constant current across its anode and cathode, which was used to power an Arm Cortex-M0+ CPU: a low-power, high-efficiency microprocessor already used in internet of things applications.
The processor performed continual calculations to replicate a typical workload, while also recording the battery's power output.
The experiment data was stored in the cloud for analysis.
There were no power outages during the six months of the test, and the cyanobacteria continued to produce electricity six months after the experiment concluded.
The results have now been published in a paper called 'Powering a microprocessor by photosynthesis'.
Professor Howe, the paper's joint senior author, believes there are two possible sources for the electricity in the device.
The cyanobacteria either make electrons directly, resulting in a current; or they create conditions in which the aluminium anode in the container corrodes, resulting in an electron-producing chemical process.
Because the anode did not degrade significantly during the experiment, the researchers assume the cyanobacteria were responsible for the majority of the current.
The researchers built the gadget using common, inexpensive, and mostly recyclable components. They believe it has the potential to power a large number of small devices.
"The growing Internet of Things needs an increasing amount of power, and we think this will have to come from systems that can generate energy, rather than simply store it like batteries," said Professor Howe.
"Our photosynthetic device doesn't run down the way a battery does because it's continually using light as the energy source."
Dr Paolo Bombelli, the first author of the paper, said he was amazed to see how consistently the system operated over a long period of time.
"We thought it might stop after a few weeks, but it just kept going," he added.
This was collaborative project between the University of Cambridge and Arm, which specialises in microprocessor design.
Arm Research developed the Arm Cortex M0+ test chip, as well as the board. The divison also set up the data-collection cloud interface used in the studies.
The study is published in the journal Energy & Environmental Science.
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