Army

Stretchable electronics

Elastomeric conductor materials that readily deform and are capable of functioning even when subjected to high strain

Materials

Panels a) and b) show photographs of a conductive composite consisting of poly(styrene-b-ethylene-co-butylene-b-styrene) containing 30 vol % nickel-coated carbon fiber connected to a Keithley 2410 source meter un-deformed and twisted 360°

Stretchable electronics have the potential to enable a wide variety of emerging applications including sensors or electronic device integration into textiles, conformable power, enhanced robotic mobility and manipulation, energy harvesting, fieldable biosensing, sensing technology, as well as exoskeletons and multifunctional conforming suits. But such applications are still largely out of reach. Methods to make stretchable electronics, and their reason for failure are listed below:

Method Problems
Use of inherently conductive polymers with conjugated backbones Extremely brittle, prone to fracture and small strains; very high melting points
Incorporated conductive fillers The most promising – carbon nanotubes (CNT’s) – have poor uniformity, high cost, and are not stretchable
Deposition of conductive materials on a flexible substrate Are not stretchable; require intricate production methods

To address the above, Army researchers have developed deformable polymer composites with controlled electrical performance during deformation through tailored strain-dependent conductive filler contact. The Army material is a deformable elastomeric conductor and includes an elastomeric polymer matrix and a conductive filler material of metal-coated carbon fibers (and related materials) uniformly dispersed in the elastomeric polymer matrix. The conductive filler material comprises non-entangled particles having an aspect ratio sufficiently large to enable the particles to remain in contact with adjacent particles so as to maintain conductive pathways in the material when the material is subjected to deformation and strain.

Related US patent application US 20150129276 A1

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