Linear Self-Focusing Acoustic Transducer

This paper describes a linear self-focusing acoustic transducer (SFAT) capable of ejecting liquid droplets and asymmetric and heavy semiconductor chips from a liquid surface. The linear SFAT is designed to have multiple distributed focal points to generate an ejection force on multiple points at a liquid surface and is shown to be capable of ejecting a single liquid droplet in the center, two droplets out of its distributed side peaks, or tall water columns from the three pressure peaks, depending on how the transducer is electrically actuated. In addition, a linear SFAT (designed for a focal length of 5mm), when actuated at its thickness mode resonance at 1.955MHz with sinusoidal pulses of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$173\mathrm{V}_{\mathrm{p}p}$</tex> for 10.2ms with a duty cycle of 1.0%, is shown to eject a silicon chip of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$12\times 4\times 0.4 \text{mm}^3$</tex> (45mg) up to 9cm height from a liquid surface, one chip per pulse.