Iteratively Calibrated S11 Thermometry for Microsecond-Scale Intra-Pulse Heating in 96-Well Plates

This work is motivated by the need to separate genuine bio-electromagnetic effects from thermal artefacts in a 2.2 GHz pulsed exposure platform for 96-well cell experiments. We repurpose the system as an S11-based thermometer by performing a low-power static heating run in a 200 µL well, aligning S11 with a fibre-optic probe and fitting a first-order heating model. A lightweight piecewise-linear S11-temperature mapping then improves the bulk temperature accuracy from an initial 0.29 °C down to the millikelvin range, with <0.1 °C agreement over a 20 °C span. Using this calibrated mapping at MHz sampling under treatment-like conditions (1 kHz pulse trains, 100 µs “on” / 900 µs “off”), we resolve reproducible intra-pulse self-heating of ~0.2 K per burst which was completely averaged out by conventional 1–10 Hz fibre thermometry.