Stem cells -- the body's master cells -- demonstrate a bizarre property never before seen at a cellular¹ level, according to a study published today from scientists at the University of Cambridge. The property -- known as auxeticity（拉胀性） -- is one which may have application as wide-ranging as soundproofing, super-absorbent sponges and bulletproof vests. Most materials when stretched will contract. For example, if one pulls on an elastic² band, the elastic itself will get thinner. The opposite is also true: squeeze a material and it will expand -- for example, if one squeezes a tennis ball between both hands, the circumference³ around the ball gets larger. However, material scientists have begun to explore auxeticity, an unusual property which has the opposite effect -- squeeze it and it will contract, stretch it and it will expand. This means that auxetic materials act as excellent shock absorbers or sponges, a fact that is being explored for various uses.

 

Until now, auxeticity has only been demonstrated in humanmade materials and very rarely in nature, such as some species of sponge. But today, in a paper published in the journal Nature Materials, a team of University of Cambridge researchers including biologists, engineers and physicists⁴, report having observed auxeticity in the nuclei⁵ of embryonic⁶ stem cells, master cells within the body which can turn into any other type of cell.

 

Dr Kevin Chalut from the Wellcome Trust-Medical Research Council Cambridge Stem Cell Institute, who led the study, says: "This is a pretty bizarre finding and very unexpected. When the stem cell is in the process of transforming into a particular type of cell, its nucleus⁷ takes on an auxetic property, allowing it to 'sponge up' essential materials from its surrounding. This property has not, to my knowledge, been seen before at a cellular level and is highly unusual in the natural world."

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