Apparatus and method for inducing controllable jets in liquids
A method for inducing a controllable jet in a transparent liquid is disclosed. The method comprises providing a gas-liquid interface, providing a laser source and generating a beam comprising a sequence of laser pulses, and focusing the beam to a target location within the liquid at a predetermined distance from the gas-liquid interface and creating a plurality of cavitation bubbles, yielding a jet directed away from the gas-liquid interface. Other methods and apparatus are also described and claimed.
1. A method for inducing a controllable jet in a transparent liquid, comprising:
providing a gas-liquid interface;
providing a laser source and generating a beam comprising a sequence of laser pulses;
focusing said beam to a target location within the liquid at a predetermined distance from the gas-liquid interface and creating a plurality of cavitation bubbles; and wherein a time interval between the laser pulses within said sequence of pulses is longer than the cavitation time of the bubble and less than the decay time of cavitation flow generated by each bubble.
2. The method according to claim 1 , wherein the step of generating a beam comprising a sequence of laser pulses includes generating laser pulses wherein each laser pulse is sufficient to create a cavitation bubble.
3. The method according to claim 1 , wherein the predetermined distance is chosen to keep integrity of the gas-liquid interface and yielding a jet directed away from the gas-liquid interface.
4. The method according to claim 1 , wherein the sequence of laser pulses comprises pulses with wavelength in the range of 0.3 to 3 μm, having a pulse energy ranging from 0.01 μJ to 100 mJ, a pulse width ranging from 10 fs to 30 ns and repetition rate ranging from 1 Hz to 100 MHz.
5. The method according to claim 1 , wherein the step of creating a plurality of cavitation bubbles comprises creating a plurality of cavitation bubbles, so that each bubble moves away from the target location before the next bubble is created.
6. The method according to claim 1 , wherein the gas-liquid interface is an air-water interface.
7. The method according to claim 1 , wherein the gas-liquid interface is a liquid vapor-liquid interface.
8. The method according to claim 1 , wherein the gas-liquid interface is an inert gas-water interface.
9. The method according to claim 1 , wherein the gas-liquid interface is substantially flat.
10. The method according to claim 1 , wherein the gas-liquid interface is curved.
11. The method according to claim 1 , wherein the step of providing the gas-liquid interface in the liquid comprises providing a transparent surface atop a container filled with the liquid and providing a gas bubble beneath the transparent surface, the gas bubble defining the gas-liquid interface.
12. The method according to claim 1 , wherein the step of providing the gas-liquid interface in the liquid comprises providing a solid holder in a container filled with the liquid and providing a gas bubble fixed on said solid holder defining the gas-liquid interface.
13. The method according to claim 12 , wherein said solid holder is a needle.
14. The method according to claim 1 , wherein the step of providing the gas-liquid interface comprises providing a liquid drop on a surface, the liquid drop defining the gas-liquid interface.
15. The method according to claim 1 , wherein the step of providing the gas-liquid interface comprises providing a capillary in a container filled with the liquid and a pump for inflating a gas bubble through said capillary creating the gas-liquid interface.
16. The method according to claim 1 comprising providing relative displacement between the target location and the gas-liquid interface for controlling the length and direction of propagation of the jet.
17. The method according to claim 1 , further comprising varying a property of the gas-liquid interface to control the jet.
18. The method according to claim 17 , wherein the property of the gas-liquid interface is selected from a group of properties including curvature and distance from the target location.
19. An apparatus for inducing a controllable jet in a transparent liquid, the apparatus comprising:
a support of liquid with a gas-liquid interface;
a laser source for generating a beam comprising a sequence of laser pulses;
a focusing optics for focusing a said beam to a target location within the liquid at a predetermined distance for creating a plurality of cavitation bubbles, yielding a jet directed away from the gas-liquid interface; wherein a time interval between the laser pulses within said sequence of pulses is longer than the cavitation time of the bubble and less than the decay time of cavitation flow generated by each bubble; and
a relative displacement facilitator for facilitating relative displacement between the objective focal point and the gas-liquid interface for setting a predetermined distance between the objective focal point and the gas-liquid interface.
20. The apparatus according to claim 19 , further provided with a facilitator for varying a property of the gas-liquid interface selected from a group of properties including a curvature of the gas-liquid interface and the distance of the target location from the gas-liquid interface.
21. The apparatus according to claim 19 , wherein the sequence of laser pulses comprises pulses with wavelength in the range of 0.3 to 3 μm, having a pulse energy ranging from 0.01 μJ to 100 mJ, a pulse width ranging from 10 fs to 30 ns and repetition rate ranging from 1 Hz to 100 MHz.