Gel compositions with tunable hardness
Gel compositions have a tunable hardness controlled by exposure to an external stimulus. Further disclosed herein are methods for making such gel compositions and devices that use such gel compositions. In one aspect, the gel compositions can be used to prepare physical 3-D replicas of the topography of a target surface.
1 . A method of forming a 3-dimensional replica of a target surface with a gel composition, the method comprising:
providing a gel composition on an optically clear substrate, the gel composition forming an optically clear material including one or more thermoplastic polymers or elastomers, one or more multifunctional plasticizers, and one or more initiators, wherein the gel composition is a curable gel composition formed of a soft gel having a Shore 00 hardness between 5 and 80, wherein the optically clear substrate is a rigid substrate, and wherein upon exposure to an external stimulus the gel composition cures from the soft gel to a Shore A hardness of at least 50;
contacting the gel composition to a target surface with an application of force applied through the optically clear substrate;
exposing the gel composition on the target surface to the external stimulus to polymerize and/or crosslink the one or more multifunctional plasticizers and to cure the gel composition into a hard gel composition having a Shore A hardness of at least 50; and
removing the hard gel composition from the target surface to provide a topographical replica of the target surface in the hard gel composition.
2 . The method of claim 1 , wherein the gel composition is curable to a Shore A hardness of at least 60.
3 . The method of claim 1 , wherein the gel composition includes a material disposed on a surface thereof opposing the optically clear substrate, the material forming a contact surface for contacting the target surface.
4 . The method of claim 3 , wherein the contact surface includes a plurality of air channels to facilitate egress of air when the contact surface is placed against the target surface for topographical reproduction.
5 . The method of claim 3 , wherein the material of the contact surface has a lower coefficient of friction than the gel composition.
6 . The method of claim 3 , wherein a side of the contact surface facing the gel composition is opaque.
7 . The method of claim 3 , wherein the contact surface includes a plurality of particles with a Shore A hardness of at least 40.
8 . The method of claim 7 , wherein the plurality of particles having an average diameter less than 10 microns.
9 . The method of claim 1 , wherein the gel composition is photocurable with ultraviolet light to the Shore A hardness of at least 60.
10 . The method of claim 1 , wherein the gel composition is photocurable to a Shore A hardness of at least 90.
11 . The method of claim 1 , wherein the external stimulus to cure the gel composition includes heat.
12 . The method of claim 1 , wherein the external stimulus to cure the gel composition includes chemical additives.
13 . The method of claim 1 , wherein the external stimulus to cure the gel composition includes light.
14 . The method of claim 1 , wherein the optically clear substrate includes a polycarbonate.
15 . The method of claim 1 , wherein the optically clear substrate includes one or more of an acrylate and a glass.
16 . The method of claim 1 , wherein the one or more thermoplastic polymers or elastomers are selected from a group consisting of polyurethanes, siloxanes, silicone rubbers, polyamides, polyesters, polyolefins, natural rubbers, and mixtures thereof.
17 . The method of claim 1 , wherein the one or more thermoplastic polymers or elastomers includes a polyurethane elastomer.
18 . The method of claim 1 , wherein the gel composition is optically clear and transmits all or substantially all visible light through the gel composition.
19 . The method of claim 1 , wherein the hard gel composition cured from the gel composition is optically clear.
20 . The method of claim 1 , wherein the gel composition includes one or more stabilizers to inhibit thermal polymerization of the gel composition, the one or more stabilizers including at least one of phenothiazine, hydroquinone, 4-methoxyphenol, and methylhydroquinone.
21 . The method of claim 1 , wherein the gel composition has a thickness between 0.1 millimeters and 3 millimeters.