Microporous dry adhesive films, methods of making, and methods of use
Provided herein are materials, methods of making materials, and methods of use, wherein the materials have switchable adhesive properties. Materials of the present disclosure can reversibly change coloration in conjunction with the changing adhesive state. The films, made from a porous polymer material, can be reversibly changed from a smooth state to a rough state, allowing for reversible and tunable gripping and/or adhesive properties.
1 . A porous polymer material having switchable adhesion, where the porous polymer material comprises: a shape memory polymeric material comprising ordered voids, wherein the porous polymer material has a macroporous layer that has a first region and second region, wherein the first region is at a top surface of the macroporous layer and the second region is under the first region, wherein the first region is about 2-3 microns thick, wherein the first region has pores with a diameter of about 300 nm, wherein the second region has pores with a diameter of about 100 nm;
wherein the porous polymer material has a starting state, a deformed state, and a recovered state;
wherein when in the deformed state, the porous polymer material has a surface roughness that is greater than when in the starting state or the recovered state; and
wherein when in the deformed state, the porous polymer material has a lower adhesion to a surface than an adhesion of the starting state or the recovered state to the surface,
wherein the macroporous layer has a thickness of about 3 micrometer to 300 micrometers.
2 . The porous polymer material of claim 1 , wherein the porous polymer material is transitioned to the deformed state from either the starting state or deformed state by exposure of the porous polymer material to a first stimulus; and
wherein the porous polymer material is transitioned to the recovered state from the deformed state by exposure of the porous polymer material to a second stimulus.
3 . The porous polymer material of claim 1 , wherein porous polymer material has the characteristic of being switchable from the deformed state to the recovered state or from the recovered state to the deformed state repeatedly.
4 . The porous polymer material of claim 1 , wherein the first stimulus is water.
5 . The porous polymer material of claim 1 , wherein the second stimulus is a solvent selected from hexane, acetone, ethanol, toluene, or vapors thereof.
6 . The porous polymer material of claim 1 , wherein
when in the deformed state, the porous polymer material has a surface root mean square roughness of about 40 nm to 200 nm; and
when in the starting state or the recovered state, the porous polymer material has a surface root mean square roughness of 5 nm to 50 nm.