System for freezing dispensed droplets of liquid
A method and apparatus for freezing a liquid droplet includes dispensing, by a liquid dispenser, a droplet of liquid into a fluid chamber containing a freezing fluid. The droplet of liquid is allowed to dwell in the freezing fluid for at least a predetermined dwell time so that the droplet of liquid freezes to a frozen droplet. The method and apparatus further includes injecting, by a gas injector, a stream of gas transversely to a surface of the freezing fluid at about where the frozen droplet is located along the surface of the freezing fluid contained in the fluid chamber so that the frozen droplet sinks in the freezing fluid.
1. A system for freezing dispensed droplets of liquid, the system comprising:
a fluid chamber containing a freezing liquid;
a liquid dispenser disposed above a surface of the freezing liquid contained in the fluid chamber and configured to dispense a droplet of liquid onto the surface of the freezing liquid contained in the fluid chamber;
a gas injector disposed above the surface of the freezing liquid contained in the fluid chamber and configured to inject a stream of gas transversely to the surface of the freezing liquid contained in the fluid chamber;
a transporter configured to transport the fluid chamber between a first position below the liquid dispenser and a second position below the gas injector,
a sensor configured to generate a signal relating to a position of the fluid chamber; and
a control unit in electrical communication with the sensor, the liquid dispenser, and the gas injector, wherein the control unit is configured to receive the signal from the sensor, to cause the liquid dispenser to dispense the droplet of liquid into the fluid chamber when the fluid chamber is in the first position, and cause the gas injector to inject the stream of gas transversely to the surface of the freezing liquid contained in the fluid chamber when the fluid chamber is in the second position.
2. The system of claim 1 , wherein the transporter comprises a carousel configured to move the fluid chamber between the first position and the second position about an axis of rotation of the carousel, and wherein the control unit is configured to determine a rotation rate or angular position of the carousel based on the signal from the sensor.
3. The system of claim 1 , wherein the sensor comprises an optical sensor coupled to the transporter and including a transmitter configured to transmit a light beam and a receiver configured to receive the light beam and at least one projection attached to the transporter and which moves between the transmitter and the receiver to block the light beam and generate the signal as the transporter transports the fluid chamber between the first position and the second position.
4. The system of claim 1 , comprising multiple fluid chambers, wherein the transporter is configured to transport each of the fluid chambers between the first position below the liquid dispenser and the second position below the gas injector.
5. The system of claim 4 , comprising multiple liquid dispensers and multiple gas injectors, wherein the transporter is configured to transport each of the fluid chambers to the first position below a respective one of the liquid dispensers, and wherein the transporter is configured to transport each of the fluid chambers to the second position below a respective one of the gas injectors.
6. The system of claim 1 , wherein the control unit is configured to cause the gas injector to start injecting the stream of gas when the transporter positions a leading edge of the fluid chamber below the gas injector and to continue injecting the stream of gas until the transporter positions a trailing edge of the fluid chamber below the gas injector.
7. The system of claim 1 , wherein the gas injector comprises a nozzle disposed above the fluid chamber, and wherein the nozzle is configured to inject the gas stream transversely to the surface of the freezing liquid contained in the fluid chamber, and wherein the system further comprises a solenoid valve controlling gas flow to the nozzle and configured to switch between a closed position to shut-off the gas stream from reaching the nozzle and an open position to permit the gas stream to reach the nozzle, and wherein the control unit is in electrical communication with the solenoid valve, and wherein the control unit is configured to receive the signal from the sensor and transmit a command to the solenoid valve to switch between the open and closed positions based on the signal.
8. The system of claim 1 , wherein the transporter is configured to transport the fluid chamber from the first position to the second position at a predetermined dwell time so that the droplet of liquid freezes to a frozen droplet before the gas injector injects the stream of gas transversely to the surface of the freezing liquid contained in the fluid chamber.
9. The system of claim 1 , wherein the freezing liquid is liquid nitrogen.
10. The system of claim 3 , wherein the transporter comprises a carousel configured to move the fluid chamber between the first position and the second position about an axis of rotation of the carousel, and wherein the at least one projection comprises a plurality of spaced-apart projections attached to the carousel and spatially arranged in a circle centered on the axis of rotation of the carousel.
11. The system of claim 10 , wherein the carousel comprises a drum and the fluid chamber is disposed within the drum, and wherein the plurality of projections are disposed on a base of the drum.
12. The system of claim 11 , wherein the plurality of projections are spatially arranged along a perimeter of the base of the drum.
13. The system of claim 12 , comprising two or more fluid chambers disposed within the drum, and wherein an angular spacing between the projections along the perimeter of the base corresponds to an angular separation between the two or more fluid chambers within the drum.