Elastic woven fabric holds body monitoring sensors still
A US company has designed an elasticated fabric that carries conductive yarns specifically for use with body monitoring systems.
Woven Electronics Corp of Simpsonville, South Carolina, has revealed more details of the work in US Patent 7 337 810. The company says the fabric stretches in the longitudinal direction so as to expand and contract in response to the size of of the torso of the wearer and any subsequent movements.
The fabric construction includes at least one conductive and inelastic yarn in the longitudinal direction, which is held between the upper and lower surfaces. The yarn is arranged in sinusoidal configurations in this longitudinal direction, breaking through one of the outer surfaces at selected distances along the length of the textile.
Moreover, the yarn is cut to expose at least one end above this outer surface. The monitoring unit–a connector and a sensor–is secured to the outer surface and a junction is made between the exposed yarn and the connector. These connector loops can be arranged in transverse rows across the fabric in staggered positions with respect to the longitudinal coordinates.
The fabric’s design holds the monitor in a stationary position on the body while the sensor captures signals from the torso, transmitting them along the conductive yarns.
Fabrics currently used in such applications are warp-knits, which suffer from a disadvantage in that the conductive yarn has to lie in a transverse plane of the fabric, according to the Patent.
The conductive yarns are positioned in the warp and can be fibres, filaments or wires. Other warp yarns are rubber or elastane (spandex). These are all woven with a number of non-elastic weft yarns. The overall fabric may be extended longitudinally between 25% and 125% from its retracted position, the resulting elongated configurations altering the sinusoidal conductive yarns in a controlled manner.
The rubber or elastane warp yarns comprise an elastane core wrapped with a cover of polyester or latex. The core can be a 46.67 tex (420 denier) monofilament while the wrap is a number of multifilaments.
Preferably the fabric has a repeating pattern of 60 picks and employs 1-12 conductive yarns. These conductive yarns are ideally a wire filament wrapped with synthetic yarns, which may be textured or not.
The fabric’s construction serves to protect the conductive yarns, while allowing them to emerge at the surface to make contact with the monitors. It also provides a soft fleece-like surface for contact with the wearer’s body.
The figure shows a section of the carrier fabric (10). This multi-ply textile has upper (12) and lower (14) surfaces and contains conductive yarns (18) that extend along the fabric passing from the top to the bottom through an intermediate region (19).
At selected points these conductive yarns breaking through to the surface where they form loops (20). Some of these loops are then cut to leave exposed ends for connection to the monitor.
Another possible use of the fabric is to shield the wearer from electromagnetic radiation.
Woven Electronics began as a division of Southern Weaving Co, which was started in 1924. The electronics business became a separate division in 1963 and is now a major supplier of electronic harnesses to military prime contractors and digital signal transmission line cables for commercial computer and test equipment manufacturers. The company employs more than 200 people, occupying 0.84 ha (90 000 square feet) building in Simpsonville, South Carolina, USA.
For further information, contact: Woven Electronics Corp, PO Box 189, Mauldin, SC 29662, USA. Tel: +1-864-963-5131. Fax: +1-864-963-1761.
E-mail: email@example.com; http://www.wovenelectronics.com
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