A mogul-patterned stretchable substrate with multidirectional stretchability and minimal fracture of layers under high stretching is fabricated by double photolithography and soft lithography. Au layers and a reduced graphene oxide chemiresistor on a mogul-patterned poly(dimethylsiloxane) substrate are stable and durable under various stretching conditions. The newly designed mogul-patterned stretchable substrate shows great promise for stretchable electronics.

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Transparent stretchable (TS) sensors capable of detecting and distinguishing touch and pressure inputs are a promising development in wearable electronics. However, realization of such a device has been limited by difficulties in achieving optical transparency, stretchability, high sensitivity, stability, and distinguishable responsivity to two stimuli simultaneously. Herein, we report a TS sensor in which touch and pressure stimuli can be detected and distinguished on a substrate with a stress-relieving three-dimensional (3D) microstructured pattern providing multidirectional stretchability and increased pressure sensitivity. The TS capacitive device structure is a dielectric layer sandwiched between an upper piezoresistive electrode of a poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)/ionic liquid composite, which enables touch and pressure stimuli to be distinguished, and a lower electrode of metal/indium tin oxide/metal multilayer. The TS sensor array was demonstrated as a wearable input device for controlling a small vehicle. The TS touch-pressure sensor has great potential to be used as a multimodal input device for future wearable electronics.

The development of omnidirectionally stretchable pressure sensors with high performance without stretching-induced interference has been hampered by many challenges. Herein, an omnidirectionally stretchable piezoresistive pressure-sensing device is demonstrated by combining an omniaxially stretchable substrate with a 3D micropattern array and solution-printing of electrode and piezoresistive materials. A unique substrate structural design and materials mean that devices that are highly sensitive are rendered, with a stable out-of-plane pressure response to both static (sensitivity of 0.5 kPa and limit of detection of 28 Pa) and dynamic pressures and the minimized in-plane stretching responsiveness (a small strain gauge factor of 0.17), achieved through efficient strain absorption of the electrode and sensing materials. The device can detect human-body tremors, as well as measure the relative elastic properties of human skin. The omnidirectionally stretchable pressure sensor with a high pressure sensitivity and minimal stretch-responsiveness yields great potential to skin-attachable wearable electronics, human-machine interfaces, and soft robotics applications.

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expected to find applications in wearable displays, [3,4] electronic skin, [5] and wearable healthcare monitoring. [6] Stretchable OLEDs can be fabricated via structural engineering [7][8][9][10] or by developing intrinsically stretchable materials. [11] Several structural engineering methods have been developed to fabricate stretchable OLEDs. For example, stretchable active-matrix OLEDs were designed in an island-bridge architecture in which "island-like" rigid OLED units were transferred on elastomeric substrates with "bridge-like" stretchable conductive materials. [9] Another approach to develop stretchable OLEDs is transfer printing of OLEDs fabricated on an ultrathin substrate to a prestretched elastomeric substrate and releasing prestrain to create a stretchable OLED with a wrinkled or wavy configuration. [7,8] Attaching OLEDs on ultrathin substrates to prestrained elastomeric substrates with long-period gratings result in stretchable OLEDs with ordered buckling, high efficiency, and good mechanical robustness. [10] High performance stretchable OLEDs have been reported based on these approaches. However, transfer processes and multiple steps are used in these approaches making fabrication complex, costly, low-yielding, and difficult to control.There has been one report on stretchable OLEDs made using intrinsically stretchable materials. [11] Meanwhile, several stretchable light-emitting devices have been demonstrated in another structure, including stretchable polymer-based light-emitting devices, [4,12] and stretchable light-emitting electrochemical cells. [13] This approach has limited the selection of materials to maintain elasticity for all constituent layers of the devices. Moreover, the fabrication of intrinsically stretchable light-emitting devices is based on solution processing of multistacked layers, which faces several problems associated with dissolution, mixing, or cracking of the underlayer. Therefore, it is still a significant challenge to directly fabricate a stretchable OLED on an elastomeric substrate by using conventional materials and fabrication processes.An indium-tin oxide (ITO) film is commonly used as a transparent anode in traditional OLEDs, and this results in several challenges in the development of stretchable OLEDs. For example, the ITO film is brittle and tends to induce cracks under mechanical deformation. [14] ITO thin films are fabricated via sputtering processes and thermal annealing at high temperature, which are incompatible with the elastomeric substrates.Stretchable organic light-emitting diodes (OLEDs) are attractive for applications in wearable displays, conformal optical biomedical devices, and healthcare monitoring. Although many stretchable OLEDs have been demonstrated, their fabrication process still faces some limitations, including fabrication complexity, high cost and low yield, as well as difficulty controlling and obtaining materials for all constituent layers. Herein, a simple approach toward a stretchable OLED is proposed by directly depositing all consti...

The on-body immunodetection of biomarkers in sweat would significantly augment the potential of wearable body-interfaced biosensors for self-testing but has been limited due to the difficulty of integrating liquid handling and immunobiosensing devices in a wearable platform. Herein, a stretchable microfluidic immunobiosensor (SMIB) patch with hollow microfibers of elastomeric nanocomposites for the highly sensitive on-body biosensing of neuropeptide Y (NPY), a stress biomarker, in human sweat is reported. The SMIB patch is composed of a stretchable liquid handling device and an electrochemical impedimetric immunobiosensor made of hollow and conductive microfibers of reduced graphene oxide (rGO) and rGO-Ag nanowires in polyurethane matrix, respectively. The patch possesses a low limit of detection of 50 fm, a large dynamic range (50 fm-1 nm), good linearity, no labeling or reagent requirements, and facile formation in a patch form factor. By combining handling of the biofluid and delivery of the washing solution by a simple finger-touch operation as well as the analytical capability of NPY with an extremely low concentration in human sweat, the SMIB patch is a promising approach toward wearable non-invasive immunodetection for self-testing.