Fig. 2: Characterization of joule heating using a pulse generator.

a The R-C discharge circuit is used to generate joule heating by connecting the electrical conductor to a pulse generator. The voltage and pulse width can be adjusted. The capacitance (C) is 4000 µF. Ranges of the current (I), voltage (V), and pulse width (pw) for the low voltage mode (LV, ≤ 500 V) are listed in the figure. b Stainless steel (SS) sheet and mesh were used in this study. The thickness of SS sheet is 12 µm. The wire diameter and aperture size of the SS mesh are 30 and 38 µm, respectively. The SS mesh allows easy removal of excess CPA solution. c The electrical conductivity (σ) of the SS sheet and mesh can be calculated from the resistance by measuring the voltage and current. n = 6 independent experiments. d Comparison of various materials for rapid warming rate. The warming rate is inversely correlated to material density (ρ), electrical conductivity (σ), and heat capacity (C_p). Details in Eq. 7 assuming same electrical current, material dimensions and pulse width. e Voltage profile when different voltage pulse widths were used. The exponential decay of measured voltage matched with the calculated voltage of a R-C discharge circuit. f Voltage profile when multiple voltage pulses were applied. g Maximum energy delivered per pulse depends on the resistance and pulse width. For R ≤ 1 Ω, the max current of 500 A is used for calculation. For R ≥ 1 Ω, the max voltage of 500 V is used for calculation. h Temperature profile of a thin film resistor (150 Ω) when subjected to a voltage pulse of 300 V, 5 ms. A thermocouple was attached to the electrically insulated surface of the resistor. The resistor was submerged in liquid nitrogen (LN₂) during the measurement. Sampling resolution was 1 ms. i Temperature change (ΔT) as a function of applied voltage. The same setup shown in h was used. n = 6 independent experiments. For c and i, data presented as mean ± s.d.