We tested the internal temperature of the photo-CDR by insertion of a temperature probe into the recess of the modified photo-CDR and monitored the temperature over time. We used a temperature probe coupled to a Raspberry Pi in order to monitor the temperature at the probe every 15 seconds. Details of the temperature probe and script for the Raspberry Pi are provided in the supplementary information. The light source chosen was the Kessil H150W 32 W 450 nm (blue). As a control we tested the that would be achieved in the reflective lamp holder that we had used previously for the purpose of shrouding the lamp to prevent excess light escaping. The reflective lamp holder, complete with mirror, was designed to maximise light intensity focused on the photo-CDR. The original design had no cooling aspect to the design, the only cooling coming from advantageous air surrounding the photo-CDR. We stopped collecting data after 10 minutes when >90 °C was observed.