Microalgae harvesting using stimuli-sensitive hydrogels

1. A harvesting device comprising:

a first end having a first opening in communication with a jacket, and a second end having a second opening in communication with an inner chamber, wherein the jacket at least partially surrounds the inner chamber;

a first valve configured to control flow of a fluid into the jacket through the first opening;

a second valve configured to control flow of a liquid into and out of the inner chamber through the second opening;

a central tube extending through the inner chamber and in communication with the second opening;

at least one bucket within the inner chamber having a horizontal mesh defining a bed, wherein the horizontal mesh holds segments of a hydrogel, and wherein the bucket is disposed at least partially adjacent to the central tube; and

a plurality of one-way check valves configured to allow passage a fluid from the jacket into the inner chamber;

wherein the central tube defines perforations configured to allow passage of a substance between the central tube and the bucket.

2. The harvesting device of claim 1 , wherein the harvesting device includes a plurality of buckets.

3. The harvesting device of claim 1 , wherein one or more of the jacket, inner chamber, or central tube is annular.

4. The harvesting device of claim 1 , wherein the inner chamber is concentric with the central tube.

5. The harvesting device of claim 1 , wherein the jacket is concentric with the central tube.

6. The harvesting device of claim 1 , further including a pump connected to the second opening.

7. The harvesting device of claim 1 , further including a gas source connected to the first opening.

8. The harvesting device of claim 1 , further including a heat source configured to heat a fluid administered into the first opening.

9. The harvesting device of claim 1 , wherein the hydrogel is a stimuli-sensitive hydrogel.

10. The harvesting device of claim 1 , wherein the hydrogel is a semi-IPN hydrogel.

11. The harvesting device of claim 1 , wherein the hydrogel comprises PNIPAAm.

12. The harvesting device of claim 1 , wherein the bucket circumferentially surrounds the central tube.

13. A method of using the harvesting device of claim 1 , the method comprising:

filling the bed with a stimuli-sensitive hydrogel;

introducing dilute algal cultures in a culture media onto the bed through the central tube;

closing the second valve;

allowing the hydrogel to absorb the culture media and swell, thereby creating a concentrated algal slurry in the inner chamber; and

opening the second valve to remove a concentrated algal slurry from the harvesting device.

14. The method of claim 13 , wherein the stimuli-sensitive hydrogel comprises a semi-IPN hydrogel.

15. The method of claim 13 , further comprising the steps of:

introducing a stimulus into the jacket through the first valve so as to force open the one-way check valves and introduce the stimulus into the inner chamber, wherein the stimulus causes the swollen hydrogel to deswell and release media; and

removing the released media from the harvesting device through the second valve.

16. The method of claim 15 , wherein the stimulus is heat or CO 2 .