Rapid volumetric rewarming of cryopreserved samples using a steerable ultrasound array
E Alcalá1, M Lobillo2, P P Pérez2
1Department of Applied Physics III, Engineering School, University of Seville. Avenida de los Descubrimientos s/n, Seville 41092, Spain; National Centre of Accelerators. C/ Thomas Alva Edison 7, Seville 41092 Spain.
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This work presents the characterization and application of a 128-element high-power High-Intensity Focused Ultrasound (HIFU) phased array for the rapid and spatially uniform rewarming of cryopreserved biological samples. The device operates 512 Watts of electrical power with electronically steerable foci, enabling sub-millimeter precision heating over centimeter-scale volumes. Using simulation-informed configurations and iterative focal cycling, we achieve warming rates exceeding 150 °C/min with spatial variations below ±10 °C in mouse organs, and 200 °C/min with ±15 °C homogeneity in agar phantoms, controlled with multiple thermocouples. These conditions are necessary to avoid recrystallization damage during thawing, demonstrating the system's ability to outperform conventional water-bath methods, especially within the critical -80 °C to -30 °C zone. The peak acoustic intensity employed for sample thawing was 15 W/cm2, with 1 ms pulse duration per active element and a 6% duty cycle, for a total HIFU exposure time of 90-120 s. Numerical studies with k-Wave and T-Array provided the acoustic field intensity and steering range that the device can produce. Thermal shielding strategies and impedance-matched acoustic paths were developed to ensure efficient energy delivery during cryogenic transitions. Our findings establish the feasibility of high-power, electronically controlled HIFU arrays as scalable, non-invasive tools for safe rewarming of cryopreserved organs, paving the way toward clinical translation and long-term organ banking.
