Ultrasonic-assisted liquid manipulation
A phased array of ultrasonic transducers may create arbitrary fields that can be utilized to manipulate fluids. This includes the translation of drops on smooth surfaces as well speeding the evaporation of fluids on wetted hands. Proposed herein is the use airborne ultrasound focused to the surface of the hand. The risk is that coupling directly into the bulk of the hand may cause damage to the cellular material through heating, mechanical stress, or cavitation. Using a phased array, the focus may be moved around, thus preventing acoustic energy from lingering too long on one particular position of the hand. While some signaling may penetrate into the hand, most of the energy (99.9%) is reflected. Also disclosed are methods to couple just to the wetted surface of the hand.
1. A method of de-wetting a human body part comprising the steps of:
establishing a transducer array having a plurality of ultrasonic transducers having known relative positions and orientations;
using the transducer array to produce an acoustic field directed at a wetted human body part; and
setting an acoustic field parameter selected from the group consisting of frequencies, amplitudes, phasings, and shapes to de-wet the wetted human body part.
2. A method as in claim 1 , wherein the acoustic field is within a resonant chamber.
3. A method as in claim 1 , wherein the human body part is also subjected to forced air.
4. A method as in claim 1 , wherein liquid on the human body part experiences improved mass-transfer.
5. A method as in claim 1 , wherein liquid on the human body part experiences drop pinch-off from capillary waves.
6. A method as in claim 1 , wherein the acoustic field is adjusted by adjusting a position or phase of at least one of the plurality of ultrasonic transducers.
7. A method as in claim 6 , wherein at least one of the plurality of ultrasonic transducers create focus regions.
8. A method as in claim 7 , wherein the focus regions are translated across the human body part.
9. A method as in claim 8 , wherein the focus regions push water off the human body part.
10. A method as in claim 9 , wherein the human body part comprises a hand.
11. A method as in claim 7 , wherein the focus regions move at a speed that improves coupling to capillary waves.
12. A method as in claim 7 , wherein the focus regions occur at a spacing that improves coupling to capillary waves.
13. A method as in claim 7 , further comprising:
translating focus fields that create converging capillary waves.
14. A method as in claim 1 , wherein the acoustic fields are arranged so that nonlinear wave steepening creates sharp features.
15. A method as in claim 1 , wherein a broadband system that creates the acoustic field has high-pressure features coupled to capillary waves.
16. A method as in claim 1 , wherein the acoustic field parameter changes as wetting thickness changes.
17. A method as in claim 16 , further comprising:
a sensor to detect wetting thickness.
18. A method as in claim 1 , wherein the acoustic field takes the form of a rotating spiral.