Biaxially Stretchable, Integrated Array of High Performance Microsupercapacitors

Abstract

We report on the fabrication of a biaxially stretchable array of high performance microsupercapacitors (MSCs) on a deformable substrate. The deformable substrate is designed to suppress local strain applied to active devices by locally implanting pieces of stiff polyethylene terephthalate (PET) films within the soft elastomer of Ecoflex. A strain suppressed region is formed on the top surface of the deformable substrate, below which PET films are implanted. Active devices placed within this region can be isolated from the strain. Analysis of strain distribution by finite element method confirms that the maximum strain applied to MSC in the strain suppressed region is smaller than 0.02%, while that on the Ecoflex film is larger than 250% under both uniaxial strain of 70% and biaxial strain of 50%. The all-solid-state planar MSCs, fabricated with layer-by-layer deposited multiwalled carbon nanotube electrodes and patterned ionogel electrolyte of poly(ethylene glycol) diacrylate and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide having high-potential windows, are dry-transferred onto the deformable substrate and electrically connected in series and parallel via embedded liquid metal interconnection and Ag nanowire contacts. Liquid metal interconnection, formed by injecting liquid metal into the microchannel embedded within the substrate, can endure severe strains and requires no additional encapsulation process. This formed MSC array exhibits high energy and power density of 25 mWh/cm(3) and 32 W/cm(3), and stable electrochemical performance up to 100% uniaxial and 50% biaxial stretching. The high output voltage of the MSC array is used to light micro-light-emitting diode (mu-LED) arrays, even under strain conditions. This work demonstrates the potential application of our stretchable MSC arrays to wearable and bioimplantable electronics with a self-powered system.