Smart Materials and applications 3

Auxetics are materials that have a negative Poisson's ratio. When stretched, they become thicker perpendicular to the applied force. This occurs due to their hinge-like structures, which flex when stretched. Auxetic materials can be single molecules or a particular structure of macroscopic matter. Such materials are expected to have mechanical properties such as high energy absorption and fracture resistance. Auxetics may be useful in applications such as body armor, packing material, knee and elbow pads, robust shock absorbing material, and sponge mops.
Scientists have known about auxetic materials for over 100 years, but have only recently given them special attention. The earliest published example of a synthetic auxetic material was in Science in 1987, entitled "Foam structures with a Negative Poisson's Ratio" by R.S. Lakes from the University of Lowa. The use of the word auxetic to refer to this property probably began in 1991.
Currently the uses for auxetics are limited, and in those applications they are probably not knowingly used for the auxetic effect itself.
Zetix is a fabric invented by Auxetics Technologies, Ltd., a UK company. Zetix is auxetic material that is so strong it absorbs and disperses the energy from explosions without breaking. Zetix combines the very expensive high-performance materials with cheaper bulk components in a 1-to-100 ratio while maintaining the blast-resistant properties of the high-performance materials.
Zetix is used in a variety of products including body armor, seat belts,window covering, dental floss, military tents, hurricane defenses and medical sutures that will not damage body tissue. Also have some very interesting applications in composite materials.
Zetix is also used in threads and ropes. Knots under tension may be more secure because auxetic material expands when stretched.
Biomedical Industry:
Key areas of application are seen in the biomedical field. Prosthetic materials, surgical implants, suture/muscle/ligament anchors and a dilator to open up blood vessels during heart surgery are all possible. Another area relates to the use of auxetic materials in piezoelectric sensors and actuators. Auxetic metals could be used as electrodes sandwiching a piezoelectric polymer, or piezoelectric ceramic rods could be embedded within an auxetic polymer matrix. These are expected to increase piezoelectric device sensitivity by at least a factor of two, and possibly by ten or a hundred times. The development of auxetic materials for micro- and nano-mechanical and electromechanical devices is also being investigated.

Auxetic Fibres:

The breakthrough development of a continuous process to produce auxetic materials in fibrous form has created the opportunity to apply their unique characteristics in a wide range of applications previously not possible. Fibres can be used in single or multiple filament structures and can be used to produce a woven structure. Some applications of auxetic fibres as:
Personal Protection ClothingCrash helmets, body armour, sports clothing.
FitrationWoven structures using auxetic fibres
Ropes, Cords & FishnetsHigh strength, lower weight
BiomedicalControlled release of drugs
Medical BandagesPrevents swelling of wound by application of wound healing agent