© 2004 Robert A. Freitas Jr. and Ralph C. Merkle. All Rights Reserved.

Robert A. Freitas Jr., Ralph C. Merkle, Kinematic Self-Replicating Machines, Landes Bioscience, Georgetown, TX, 2004.

B.4.4.4 Acoustic Heating

In conventional medical ultrasound [228], dissipation of vibrational energy in aqueous tissues can produce heating rates of ~1 K/minute if applied at ~50,000 W/m² at 3 MHz, which is considered hazardous, and ultrasound intensities of ~2 x 10⁷ W/m² at the point of action are used to cauterize liver tissue after surgery [3263]. Continuous ultrasound exposure to 2000-6000 W/m² at 0.1-10 MHz raises human soft tissue temperature by 1 K at equilibrium, which is considered safe [3264]. Acoustic sonoluminescence in nonaqueous liquids [3151] typically requires power intensities in the range 0.4-3 x 10⁶ W/m² >> I_acoustic = 6100 W/m². As noted at the top of this Section, both acoustically generated solvent thermal gradients and thermal expansion of the device are expected to be minor or insignificant factors.

Last updated on 13 August 2005