Compliant yet tough hydrogel systems as ultrasound transmission agents
Method for making a tough and compliant hydrogel. A precursor hydrogel is made of a first polymer selected to maintain high elasticity and a second polymer selected to dissipate mechanical energy. The precursor hydrogel is stretched to a multiple of its original length to form a pre-stretched hydrogel. The pre-stretched hydrogel is allowed to relax and is soaked in a biocompatible solvent to reach equilibrium swelling of the pre-stretched hydrogel whereby shear modulus of the hydrogel is reduced.
1. Method for making a tough and compliant hydrogel comprising:
combining a polymer network selected to maintain elasticity and a sacrificial chain polymer network to dissipate mechanical energy to form an interpenetrating hydrogel;
stretching the interpenetrating hydrogel a first time to a first multiple of its original length to form a pre-stretched hydrogel;
allowing the pre-stretched hydrogel to relax;
soaking the relaxed hydrogel in a biocompatible solvent to reach equilibrium swelling of the hydrogel; and
stretching the interpenetrating hydrogel a second time to a second multiple of its original length wherein the second multiple is greater than the first multiple, whereby shear modulus of the hydrogel is reduced.
2. The method of claim 1 wherein the multiple of its original length is in the range of 2-10.
3. The method of claim 1 wherein the polymer network is selected from the group consisting of polyacrylamide, polyethylene glycol, poly (vinyl alcohol), poly (N-isopropyl acrylamide), and poly (2-hydroxyethylmethacrylate).
4. The method of claim 1 wherein the sacrificial chain polymer network is selected from the group consisting of alginate, hyaluronic acid, collagen, agarose, gelatin, fibrin and chitosan.