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Transfer printing, a two-step process (i.e. picking up and printing) for heterogeneous integration, has been widely exploited for the fabrication of functional electronics system. To ensure a reliable process, strong adhesion for picking up and weak or no adhesion for printing are required. However, it is challenging to meet the requirements of switchable stamp adhesion. Here we introduce a simple, high fidelity process, namely tape transfer printing(TTP), enabled by chemically induced dramatic modulation in tape adhesive strength. We describe the working mechanism of the adhesion modulation that governs this process and demonstrate the method by high fidelity tape transfer printing several types of materials and devices, including Si pellets arrays, photodetector arrays, and electromyography (EMG) sensors, from their preparation substrates to various alien substrates. High fidelity tape transfer printing of components onto curvilinear surfaces is also illustrated.

Enhanced safety of flexible batteries is an imperative objective due to the intimate interaction of such devices with human organs such as flexible batteries that are integrated with touch-screens or embedded in clothing or space suits. In this study, the fabrication and testing of a high performance thin-film Li-ion battery (LIB) is reported that is both flexible and relatively safer compared to the conventional electrolyte based batteries. The concept is facilitated by the use of solid polymer nanocomposite electrolyte, specifically, composed of polyethylene oxide (PEO) matrix and 1 wt% graphene oxide (GO) nanosheets. The flexible LIB exhibits a high maximum operating voltage of 4.9 V, high capacity of 0.13 mA h cm(-2) and an energy density of 4.8 mW h cm(-3). The battery is encapsulated using a simple lamination method that is economical and scalable. The laminated battery shows robust mechanical flexibility over 6000 bending cycles and excellent electrochemical performance in both flat and bent configurations. Finite element analysis (FEA) of the LIB provides critical insights into the evolution of mechanical stresses during lamination and bending.

The structure and properties of poly(tert-butylstyrene-b-hydrogenated isoprene-b-sulfonated styrene-b-hydrogenated isoprene-b-tert-butylstyrene) (tBS-HI-SS-HI-tBS) films were investigated as a function of "wet−dry cycles", where one "cycle" is defined as a 24 h soak in deionized water followed by a 24 h drying period in air. Films were characterized with a variety of complementary measurements that include X-ray scattering, infrared spectroscopy, water uptake, impedance spectroscopy, and tensile tests. We find that cycling drives a structural transition toward increasingly interconnected SS domains, which is favorable for water and ion transport. However, cycling can also induce mechanical deformations that reduce ductility, swelling, and water uptake. The significance of this trade-off is illustrated by comparing the properties for two film thicknesses as a function of cycle number: The ductility of thinner films (15 μm) is lost after four cycles, an effect that is correlated with the appearance of macroscale buckles, and the extent of swelling is also reduced. Therefore, the transport properties reflect a balance between the increased SS domain interactions and reduced water content. The ductility in thick films (30 μm) also declines with cycling, but to a lesser extent, and these systems retain their ability to swell through six cycles. Therefore, the transition to a network-like SS structure enhances both water uptake and transport. These systematic studies demonstrate that successive wet−dry cycles can lead to complex changes in the performance of amphiphilic block copolymer films, which may complicate their design for applications in water treatment or protonconducting layers in electrochemical devices.

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Stretchable batteries are needed to accommodate deformable geometries in tantalizing applications such as smart textiles, biomedical implants, and stretchable electronics. An increasing number of studies have focused on flexible and bendable batteries, but very few have investigated a stretchable lithium ion battery in which some or all components, including the electrodes, electrolyte, and encapsulation may be stretched. Here, we report the design, fabrication and characterization of a stretchable-sliding battery where the electrodes can slide, and the solid polymer electrolyte is stretched. The battery consists of a single solid polymer electrolyte film sandwiched between two sliding layered electrodes on each side. The two cathode layers are based on LiFePO4 active material, and the two anode layers are graphite based. The stretchable polymer electrolyte is composed of a specific blend of polyethylene oxide (PEO) of 100k and 600k molecular weights to enhance both the ionic conductivity and mechanical properties. Results show that the capacity of the stretchable-sliding battery increases at small tensile strains, but can degrade at larger strains. Tensile stress-strain curves of the stretchable battery and its components until failure are also presented. In situ strain-dependent electrochemical measurements provide critical insights on the stretching and sliding mechanisms in the battery. This study further validates the dual-functionality of the PEO solid electrolyte as both a stretchable film and a lithium ion conductor in a charged/discharged battery. This stretchable-sliding battery configuration can offer an experimental platform for in situ characterizations of solid polymer electrolyte films subjected to stretching inside an active electrochemical cell.

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