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Letter

Nature Materials 5, 48–51 (1 January 2006) | doi:10.1038/nmat1553

Surprising shrinkage of expanding gels under an external load

Seon Jeong Kim , Geoffrey M. Spinks , Shona Prosser , Philip G. Whitten , Gordon G. Wallace & Sun I. Kim

Hydrogels are fascinating and useful in that they can show large volume changes in response to various stimuli, such as temperature or chemical environment. Here we report the peculiar observation that chemically crosslinked hydrogels that normally expand owing to a change in electrolyte pH can be made to shrink in certain circumstances.