Steve Mould

A New Type of Levitation

The video introduces a previously unseen form of ultrasonic levitation that emerged from a torpedo guidance investigation. Engineer Bob Collins noticed a glass lens sliding off an ultrasonic transducer, prompting a deeper look that revealed a levitating micro‑gap when the device operated at its resonant frequency of roughly 30 kHz. The levitation arises from rapid compression and expansion of the thin air layer between the transducer and a nearby surface. Because the downstroke squeezes air harder than the upstroke releases it—exacerbated by nonlinear pressure‑volume relationships and drag in the narrowing gap—a net upward airflow develops, creating enough pressure to support the transducer’s weight at an equilibrium gap of about 100 microns. This mechanism differs from standing‑wave traps and bristle‑bot friction reduction. Bob demonstrated the effect by breaking an electrical circuit when the transducer lifted, confirming a true gap. The principle is already employed to transport silicon wafers in clean‑room fabs, where precise, contact‑free handling is essential. The presenter also explored adapting the technology for an “ultrasonic air‑hockey” table, confronting practical hurdles such as sourcing piezoelectric transducers and avoiding standing‑wave node dead spots. If refined, this pump‑like levitation could enable low‑friction conveyance systems, novel consumer gadgets, and quieter, energy‑efficient handling equipment. However, commercial adoption hinges on affordable, well‑matched transducers and control electronics capable of maintaining the precise phase relationships required for stable operation.