Useful work is a better milestone than an impressive open-circuit voltage. A demonstration can ask whether a device completes a defined task reliably, rather than merely whether an electrical signal exists.
A primary-source example
Bombelli and colleagues reported powering an Arm Cortex-M0+ compute block with an aluminium-anode biological system. The accepted manuscript describes alternating 45 minutes of calculation and 15 minutes of standby, with mean drawn power of 1.05 microwatts over the reported 27-week run.
The system-management controller and monitoring electronics used external USB power. This was not autonomous power for the complete monitoring and communications installation. The authors also discuss possible coexistence of biological electron production and biologically assisted aluminium oxidation. The result should not be simplified to a proven pure-photosynthesis energy balance.
Choose the task before choosing the headline
For a proposed sensor, write down its sleep draw, measurement draw, transmission burst, duty cycle and minimum operating voltage. Then measure whether the source and any storage actually support that workload through darkness and recovery. Computing, sensing and transmitting are different loads.
Primary source and access: Bombelli et al. (2022); accepted manuscript, Figure 1 and pages 6–9 inspected. Supplementary files and raw data were not reanalysed. This is an external demonstration, not MaxwellX hardware or a commercial readiness claim.