Many types of conductive fibers have been proposed for wearable electronic devices, but none of them are suitable for high tech gadgetry. For instance, metallized polymer fibers and bi-component fibers are unacceptable due to their high resistivity. Stainless steel filaments undergo metal fatigue and are very difficult to solder. Titanium is not subject to metal fatigue but is cost prohibitive. Carbon nano tubes are hazardous and extra ordinary expensive.
A project funded by US army was initiated to resolve the current technological challenges. The project objectives were to demonstrate the feasibility of producing highly conducting textile grade wires of 10-50 microns, with electrical resistance not more than five times that of a copper wire, and the core diameter approaching 60% of the fiber diameter.
Another objective was to incorporate these micro conductors into textile and connect them to electronic components. The ability to connect component via USB was also of interest.
After an intensive research effort, EY Technologies in conjunction with U.S. Army has introduced a novel method of producing micro wires that are truly flexible, solderble, weaveble, knittable, and wearable. Insulated wires of 25-75 microns have been developed and many thousands of meters have been produced in commercial scale. These conductive filaments of over 50% metal core exhibit maximum conductivity at minimum power usage. Since the bending stress is a function of wire diameter, the new finer wires are less prone to fatigue failures; a major concern in electro-textile applications.
A pilot line containing top notch equipments was built. The automated line is equipped with high accuracy micro processors and servo motors driven by laser and high speed cameras. The system is capable of accurately control the fiber and core diameters at 100% core/clad inspection. A carefully designed test matrix was conducted and the best combination of polymer and metal containing no hazardous components were identified. Twelve different polymers were selected for their superior performance in wearable electronics. Seven different alloys were tested as the core and two indium alloys were selected for their superior electrical conductivity and formability into micro-wires. An elaborated method of joining the conductive core was introduced.
This method was successfully utilized to connect electronic devices to micro wires that were woven or knitted into fabrics. The method was further employed to build micro-wire based USB cables and computer components were successfully connected using micro wires. Several micro-wire filaments were combined with nylon, PET, cotton, and wool yarns. The multifilament yarns were then processed on commercial textile machineries and many yards of conductive fabrics were made. It was also shown that the strength of even single micro wire was more than adequate for full scale weaving, flat bed knitting, and circular knitting.
The conductive fabrics were cleaned using washer/dryer at abusive conditions. The robustness of the connected conductive fabrics and their adaptability in commercial world was proven. Unquestionably, the performance of the developed products is far superior to current wearable electronics that never gained user acceptability. The new conductive fibers mark a historical milestone and open up new era to numerous intelligent wearable products with improved comfort and conformability. EY Technologies, a worldwide dominate supplier of conductive yarns, is extremely well positioned to both manufacture and market the novel conducting fibers.
EY Technologies is now investigating the commercialization of micro-wires in variety of applications such as Electroluminescent, Energy Harvesting, Strain Sensors, Rechargeable Batteries, Fiber Actuators for Patient Rehabilitation, Sensors, Wearable Capacitors, etc.
Recently EY has collaborated with so called “smart textile” developers providing enabling technologies. Utilizing EY’s network of customers, collaborators and co-developers, new products will be introduced into the mainstream of “smart textiles” including interactive data handling, smart clothing, switching, and other microelectronics integrations. EY Technologies will also serve the military interests in smart fabrics as its principal market of development.
EY Technologies completed a $729,000.00 SBIR development program for the U.S. Army in October 2009
EY Technologies Micro-Wires
