Lock-Release Polymerization

Abstract

Techniques are provided to independently control 3D shape and chemistry of rapidly produced colloids. A pre-polymer mixture including a monomer is made to flow into a channel with insular relief in a wall at a known location of the channel. A stimulus that polymerizes the pre-polymer mixture is directed onto the known location to form a structure locked in place at the known location by the insular relief. A pressure is applied to the channel that is sufficient to deflect the wall having the insular relief sufficiently to release a hydrogel particle comprising the structure.

1 . A method for synthesizing a hydrogel particle comprising:
 a) flowing a pre-polymer mixture comprising a monomer into a channel with an insular relief in a wall at a known location of the channel;   b) directing, onto the known location, a stimulus that polymerizes the pre-polymer mixture to form a structure locked in place at the known location by the insular relief; and   c) applying to the channel a pressure that is sufficient to deflect the wall having the insular relief sufficiently to release a hydrogel particle comprising the structure.   
     
     
         2 . A method as recited in  claim 1 , wherein the channel is in a microfluidic device, the structure is a microstructure, and the hydrogel particle is a hydrogel microparticle. 
     
     
         3 . A method as recited in  claim 1 , wherein directing the stimulus to form the structure further comprises directing the stimulus that has a particular two dimensional (2D) shape to form the structure having the same 2D shape. 
     
     
         4 . A method as recited in  claim 3 , wherein:
 the pre-polymer mixtures comprises a photo-initiator; and   directing the stimulus that has the particular 2D shape to form the structure having the same 2D shape further comprises projecting illumination through a photo mask having the particular 2D shape to form the structure having the same 2D shape.   
     
     
         5 . A method as recited in  claim 1 , further comprising, before step c:
 d) flowing a different second pre-polymer mixture into the channel; and   e) directing, near the known location, a supplemental stimulus that polymerizes the second pre-polymer mixture to form a supplemental structure near the known location,   wherein the supplemental structure is cross-linked with the structure locked in place at the known location.   
     
     
         6 . A method as recited in  claim 5 , wherein the supplemental structure also overlaps the structure locked in place at the known location. 
     
     
         7 . A method as recited in  claim 5 , wherein.
 the second pre-polymer mixtures comprises a photo-initiator; and   directing the supplemental stimulus to form the supplemental structure further comprises projecting illumination through a photo-mask having a supplemental two dimensional (2D) shape to form the supplemental structure having the same supplemental 2D shape.   
     
     
         8 . A method as recited in  claim 1 , wherein the walls of the channel comprise polydimethylsiloxane (PDMS). 
     
     
         9 . A method as recited in  claim 1 , wherein the pressure is greater than about five pounds per square inch. 
     
     
         10 . A method as recited in  claim 1 , wherein the wall with insular relief has a thickness of about 200 microns and a width of the wall is about 1000 microns. 
     
     
         11 . A method as recited in  claim 1 , wherein:
 during step c, the wall having the insular relief is deflected a deflection distance at least about 100 microns under pressures above about five pounds per square inch; and   a height of the insular relief is less than the deflection distance.   
     
     
         12 . A method as recited in  claim 1 , wherein:
 during step c, the wall having the insular relief is deflected a deflection distance at least about 250 microns under pressures above about five pounds per square inch; and   a height of the insular relief is less than the deflection distance.   
     
     
         13 . A method as recited in  claim 1 , wherein the monomer is poly(ethylene glycol) diacrylate (PEG DA). 
     
     
         14 - 21 . (canceled) 
     
     
         22 . A hydrogel microparticle having an arbitrary 2D shape and relief in a third dimension comprising a plurality of non-parallel patterned chemistries. 
     
     
         23 . A hydrogel microparticle having an arbitrary 2D shape and relief in a third dimension comprising a first portion of the 2D shape and a different second portion of the 2D shape, wherein the first portion swells in response to a range of pH values and the second portion does not swell in response to the range of pH values. 
     
     
         24 . A hydrogel microparticle as recited in  claim 23  wherein the range of pH values represents neutral to alkaline conditions.