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 liquid manipulation comprising the steps of:
establishing a transducer array having a plurality of ultrasonic transducers having known relative positions and orientations;
defining a plurality of control fields wherein each of the plurality of control fields has a known spatial relationship relative to the transducer array;
defining a control surface onto which the plurality of the control fields will be projected;
wherein the control surface is human skin;
orienting the control fields onto the control surface so that liquid on the control surface is adjusted using a spiral pattern of high acoustic pressure to produce capillary waves.
2. The method as in claim 1 , wherein the plurality of control fields are dynamically updated as the liquid is adjusted.
3. The method as in claim 1 , wherein the plurality of control fields induce cavitation in the liquid.
4. The method as in claim 1 , wherein positions of the transducer array are altered to adjust the liquid.
5. The method as in claim 1 , wherein the human skin is a human hand.
6. The method as in claim 1 , wherein the capillary waves are described as:
ω
2
=
α
k
3
ρ
,
wherein ω is angular frequency, κ is wave number, α is surface tension and ρ is density of the liquid.
7. The method as in claim 1 , wherein the capillary waves include higher frequency components near edges of the capillary waves.
8. The method as in claim 1 , wherein the spiral pattern of high acoustic pressure comprises oscillating pressure fields that launch the capillary waves into a convergence point of high pressure.
9. The method as in claim 1 , wherein the spiral pattern of high acoustic pressure comprises at least one common centers pushing the capillary waves into a focus.
10. The method as in claim 1 , wherein the adjustment involves position of the liquid.
11. The method as in claim 1 , wherein the adjustment involves thickness of the liquid.
12. The method as in claim 1 , wherein the adjustment is flow velocity of the liquid.