Systems and Methods for Fabricating Water-Responsive Actuators

Abstract

Water-responsive actuators and methods for creating water responsive actuators are disclosed. In some embodiments, the disclosed subject matter includes a first layer, for example a plastic tape, and a second layer, for example bacterial spores and cured adhesive. The second layer can be created in a pattern. The pattern can include joints, which can contract when exposed to dry air and can thereby bend the actuator, and can expand when exposed to humid air and thereby return the actuator its original position.

1 . A method for fabricating a water-responsive actuator, using a solution including bacterial spores and a UV-curable adhesive suspended in a solvent, comprising:
 depositing the solution onto a substantially planar layer of flexible material that substantially maintains its shape in the presence of water;   applying UV light to the deposited solution to thereby cure at least a portion of the deposited solution to form a water-responsive layer; and   removing uncured deposited solution, if any.   
     
     
         2 . The method of  claim 1 , wherein the bacterial spores comprise  Bacillus Subtilis . 
     
     
         3 . The method of  claim 1 , wherein the bacterial spores and the UV-curable adhesive are provided in a ratio of about 1:1 by volume. 
     
     
         4 . The method of  claim 1 , wherein the bacterial spores and the UV-curable adhesive are provided in a ratio of about 13:7 by volume. 
     
     
         5 . The method of  claim 1 , wherein the bacterial spores and the UV-curable adhesive are provided in a ratio of about 3:2 by volume. 
     
     
         6 . The method of  claim 1 , wherein the UV-curable adhesive comprises an adhesive having a Young’s Modulus of about 1-2 GPa. 
     
     
         7 . The method of  claim 1 , wherein the method further comprises removing the water-responsive layer from the substantially planar layer. 
     
     
         8 . A water-responsive actuator comprising:
 a substantially planar first layer comprising a flexible material that substantially maintains its shape in the presence of water; and   a second layer positioned on a surface of the first layer;   wherein the second layer comprises a cured solution including a bacterial spore and a cured adhesive, the second layer being water-responsive to permit repeatable actuation in the presence of water.   
     
     
         9 . The actuator of  claim 8 , wherein the bacterial spore comprises a  Bacillus Subtilis  spore. 
     
     
         10 . The actuator of  claim 8 , wherein the second layer comprises a patterned layer. 
     
     
         11 . The actuator of  claim 8 , wherein the water responsive actuator further comprises an electrical heater adapted to affect local humidity. 
     
     
         12 . The actuator of  claim 8 , wherein the second layer is adapted to be electrically conductive. 
     
     
         13 . The actuator of  claim 8 , wherein the cured adhesive comprises an adhesive having a Young’s Modulus of about 1-2 GPa. 
     
     
         14 . The actuator of  claim 8 , wherein the second layer is adapted for actuation by contact with liquid water. 
     
     
         15 . The actuator of  claim 8 , wherein the second layer is adapted for actuation by contact with liquid water and to return to an initial shape by cessation of such contact with liquid water. 
     
     
         16 . The actuator of  claim 8 , wherein the second layer is adapted for actuation by contact with air having a relative humidity of at least 30%. 
     
     
         17 . The actuator of  claim 8 , wherein the second layer is adapted for actuation by contact with air having a first relative humidity and to return to an initial shape by contact with air having a second relative humidity, wherein said second relative humidity is at least 10% less than said first relative humidity. 
     
     
         18 . A solution for making a water-responsive material comprising:
 a UV curable adhesive;   a water-responsive bacterial spore; and   a solvent; 
 wherein the adhesive is provided in a ratio of about 25% to about 50% by volume to the solution. 
     
     
         19 . The solution of  claim 18 , wherein the water responsive bacterial spore comprises a  Bacillus Subtilis  spore. 
     
     
         20 . The solution of  claim 8 , wherein the adhesive comprises an adhesive cured by light having a wavelength between about 200 nanometers and about 700 nanometers. 
     
     
         21 . The solution of  claim 8 , wherein the solvent comprises acetone and/or toluene. 
     
     
         22 . The method of  claim 1 , wherein the flexible material is a moisture permeable material. 
     
     
         23 . The method of  claim 1 , wherein the flexible material is selected from the group consisting of fleece, cotton, polyester, nylon, spandex, wool, and combinations thereof.