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Sounds exotic.

U.S. Patent 7,858,055 (December 28, 2010), "Moisture Sensitive Auxetic Material," WanDuk Lee, SangSoo Lee, CholWoh Koh, and Jin Heo (Kimberly-Clark Worldwide, Inc., Neenah, Wisconsin, USA).

Auxetic materials have a negative Poisson's ratio, meaning that under tensile stress, the area perpendicular to the tensile axis increases rather than decreases. Applications have been limited because of production difficulties. Lee et al of Kimberly-Clark have developed a material that is auxetic when exposed to moisture and external forces. This material consists of a stiff, moisture-activated shrinking filament wrapped in a helix around a rubber core. When exposed to moisture, the helical fiber shrinks by 20% or more. This shrinkage pulls the rubber, forming pores and resulting in an overall auxetic behavior. The fiber can be a modified cellulose or a polyvinyl alcohol fiber and the rubber can be natural rubber, silicone, or polyurethane.

Roger D. Corneliussen is Professor Emeritus of Materials Engineering, Drexel University, in Philadelphia, Pennsylvania, USA. He is editor of Maro Polymer Alerts and the Maw Polymer website ( He has been active in SPE since 1962 and has served on the Board of the Philadelphia Section and as SPE Councilor. For Maro Patent Alerts, he reviews all U.S. Patents weekly, makes links to the polymer-related patents, and sends the links daily to subscribers. These patent abstracts are based on the weekly selection process. To sample Maro Patent Alerts, email a request to

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Title Annotation:industry PATENTS
Author:Corneliussen, Roger
Publication:Plastics Engineering
Article Type:Brief article
Geographic Code:1USA
Date:Oct 1, 2011
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