Architected materials that actively respond to external stimuli hold tantalizing prospects for applications in energy storage, wearable electronics, and bioengineering. Molybdenum disulfide, an excellent two-dimensional building block, is a promising candidate for lithium-ion battery anode. However, the stacked and brittle two-dimensional layered structure limits its rate capability and electrochemical stability. Here we report the dewetting-induced manufacturing of two-dimensional molybdenum disulfide nanosheets into a three-dimensional foam with a structural hierarchy across seven orders of magnitude. Our molybdenum disulfide foam provides an interpenetrating network for efficient charge transport, rapid ion diffusion, and mechanically resilient and chemically stable support for electrochemical reactions. These features induce a pseudocapacitive energy storage mechanism involving molybdenum redox reactions, confirmed by in-situ X-ray absorption near edge structure. The extraordinary electrochemical performance of molybdenum disulfide foam outperforms most reported molybdenum disulfide-based Lithium-ion battery anodes and state-of-the-art materials. This work opens promising inroads for various applications where special properties arise from hierarchical architecture.

We present a flexible acoustic sensor that has been designed to detect wheezing (a common symptom of asthma) while attached to the chest of a human. We adopted a parallel-plate capacitive structure using air as the dielectric material. The pressure (acoustic) waves from wheezing vibrate the top diaphragm of the structure, thereby changing the output capacitance. The sensor is designed in such a way that it resonates in the frequency range of wheezing (100–1000 Hz), which presents twofold benefits. The resonance results in large deflection of the diaphragm that eradicates the need for using signal amplifiers (used in microphones). Second, the design itself acts as a low-pass filter to reduce the effect of background noise, which mostly lies in the >1000-Hz frequency range. The resulting analog interface is minimal, and thus consumes less power and occupies less space. The sensor is made up of low-cost sustainable materials (aluminum foil) that greatly reduce the cost and complexity of manufacturing processes. A robust wheezing detection (matched filter) algorithm is used to identify different types of wheezing sounds among the noisy signals originating from the chest that lie in the same frequency range as wheezing. The sensor is connected to a smartphone via Bluetooth, enabling signal processing and further integration into digital medical electronic systems based on the Internet of Things (IoT). Bending, cyclic pressure, heat, and sweat tests are performed on the sensor to evaluate its performance in simulated real-life harsh conditions.

We present detailed shape-based analyses to compare the performance of metal foil-based capacitive pressure sensors based on the shape of the diaphragm (top electrode). We perform a detailed analysis on the use of new material and deflection in various shaped diaphragms to act as a performance indicator for pressure-based capacitive sensors. A low-cost, recyclable, and readily available material is used to present an alternative to the expensive materials used in conventional pressure sensors. Diaphragms of five different shapes (circle, ellipse, pentagon, square, and rectangle) are fabricated and analyzed. Mathematical, FEM, and experimental tests are performed for capacitive sensors fabricated in five different shapes. The mathematically calculated deflection for each shaped diaphragm is compared with the results of the corresponding FEM simulations. Two different experiments are performed to verify the performance of pressure sensors.

A spiral interconnect array is a commonly used architecture for stretchable electronics, which accommodates large deformations during stretching. Here, we show the effect of different geometrical morphologies on the deformation behavior of the spiral island network. We use numerical modeling to calculate the stresses and strains in the spiral interconnects under the prescribed displacement of 1000 μm. Our result shows that spiral arm elongation depends on the angular position of that particular spiral in the array. We also introduce the concept of a unit-cell, which fairly replicates the deformation mechanism for full complex hexagon, diamond, and square shaped arrays. The spiral interconnects which are axially connected between displaced and fixed islands attain higher stretchability and thus experience the maximum deformations. We perform tensile testing of 3D printed replica and find that experimental observations corroborate with theoretical study.