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High linearity is important for stretchable strain sensors. Herein, we propose a new strategy of brittle-layer-tuned microcrack propagation to achieve high-linearity resistive-type stretchable strain sensors by using a highly facile and effective method. It is achieved by introducing a brittle layer in between the conductive layer and the polymeric substrate followed by a pre-crazing process. A high linearity (R2 ≈ 0.9721) within 100% strain is achieved, which is an important development for resistance-type stretchable strain sensors. The brittle layer also increases the sensitivity by around three times. Meanwhile, the sensor can be easily patterned and the strong adhesion between the active materials and elastic substrate can be realized through this approach. Then, to demonstrate the feasibility and wide applicability of this brittle layer strategy, PDMS and Ecoflex substrates are employed for the strain sensors preparation. The fabricated sensors exhibit high stretchability up to 100% and high sensitivity with a gauge factor (GF) up to 460.9 based on PDMS. Moreover, an ultrahigh GF value of 41488.8 is obtained by using the Ecoflex substrate. Besides, the working mechanism, reliability and wearable applications are investigated and demonstrated. The superior sensing capabilities of the prepared strain sensors indicate great potential in the fields of integrated stretchable and wearable devices. Our proposed strategy opens up a new perspective to achieve high-performance stretchable strain sensors.

In recent years, real-time health management has received increasing attention, benefiting from the rapid development of flexible and wearable devices. Conventionally, flexible and wearable devices are used for collecting health data such as electrophysiological signals, blood pressure, heart rate

Stretchable thin-film conductors are basic building blocks in advanced flexible and stretchable electronics. Current research mainly focuses on strategies to improve stretchability and widen the range of applications of stretchable conductors. However, stability should not be neglected, and the electrical failure mode is one of the most common stability issues that determines the current range and duration in a circuit. In this work, we report the electrical failure mechanism of stretchable conductors. We find a special failure mode for the stretchable conductors, which can be attributed to the coupling effect between local thermal strains and dynamic resistance changes of the thin film. This creates a vicious circle that significantly differs from traditional conductors. Physical parameters related to this special failure mode are investigated in detail. It is found that this mechanism is applicable to different kinds of stretchable conductors. Based on this finding, we also explore methods to modulate the failure of stretchable conductors. The failure mechanism found here provides a fundamental understanding of the current effect of stretchable circuits and is crucial for designing stable stretchable bioelectrodes and circuits.

The field of engineered living materials aims to construct functional materials with desirable properties of natural living systems. A recent study demonstrated the programmed self-assembly of bacterial populations by engineered adhesion. Here we use this strategy to engineer self-healing living materials with versatile functions. Bacteria displaying outer membrane-anchored nanobody-antigen pairs are cultured separately and, when mixed, adhere to each other to enable processing into functional materials, which we term living assembled material by bacterial adhesion (LAMBA). LAMBA is programmable and can be functionalized with extracellular moieties up to 545 amino acids. Notably, the adhesion between nanobody-antigen pairs in LAMBA leads to fast recovery under stretching or bending. By exploiting this feature, we fabricated wearable LAMBA sensors that can detect bioelectrical or biomechanical signals. Our work establishes a scalable approach to produce genetically editable and self-healable living functional materials that can be applied in biomanufacturing, bioremediation and soft bioelectronics assembly.

A complementary metal–oxide–semiconductor (CMOS) application-specific integrated circuit (ASIC) has been developed to generate arbitrary, dynamic phase patterns for acoustic hologram applications. An experimental prototype has been fabricated to demonstrate phase shaping. It comprises a cascadable $1 \times 9$ array of identical, independently controlled signal generators implemented in a 0.35- $\mu \text{m}$ minimum-feature-size process. It can individually control the phase of a square wave on each of the nine output pads. The footprint of the integrated circuit is $1175 \times 88 \,\,\mu \text{m}^{2}$ . A 128-MHz clock frequency is used to produce outputs at 8 MHz with a phase resolution of 16 levels (4 bits) per channel. A $6 \times 6$ air-coupled matrix array ultrasonic transducer was built and driven by four ASICs, with the help of commercial buffer amplifiers, for the application demonstration. Acoustic pressure mapping and particle manipulation were performed. In addition, a $2 \times 2$ array piezoelectric micromachined ultrasonic transducer (PMUT) was connected and driven by four output channels of a single ASIC, demonstrating the flexibility of the ASIC to work with different transducers and the potential for direct integration of CMOS and PMUTs.

Stretchable microfluidic sensors have recently been developed and employed in many sensing applications. However, they are still in their early stage of development and facing considerable challenges, such as practical system integration due to the limitation of costs, wired connections, and sensitivity. In this paper, we present a compact soft wireless battery-free radio frequency identification (RFID) stretchable sensor based on microfluidic technology. The proposed RFID sensor has high sensitivity and is able to be stretched to 160% of its original size. Moreover, the sensor is completely wireless powered and battery-free. It can be fully embedded into sensor carriers, such as robots to eliminate wires, reduce the weight, and increase the agility. Difference to known received signal strength indicator (RSSI) techniques for RFID sensing monitoring, resonance frequency shift is used in this paper, significantly increasing the measurement accuracy, usefulness, and reliability for many practical applications.

The ignition of flammable liquids and gases in offshore oil and gas environments is a major risk and can cause loss of life, serious injury, and significant damage to infrastructure. Power supplies that are used to provide regulated voltages to drive motors, relays, and power electronic controls can produce heat and cause sparks. As a result, the European Union requires ATEX certification on electrical equipment to ensure safety in such extreme environments. Implementing designs that meet this standard is time-consuming and adds to the cost of operations. Soft robots are often made with soft materials and can be actuated pneumatically, without electronics, making these systems inherently compliant with this directive. In this paper, we aim to increase the capability of new soft robotic systems moving from a one-to-one control-actuator architecture and implementing an electronics-free control system. We have developed a robot that demonstrates locomotion and gripping using three-pneumatic lines: a vacuum power line, a control input, and a clock line. We have followed the design principles of digital electronics and demonstrated an integrated fluidic circuit with eleven, fully integrated fluidic switches and six actuators. We have realized the basic building blocks of logical operation into combinational logic and memory using our fluidic switches to create a two-state automata machine. This system expands on the state of the art increasing the complexity over existing soft systems with integrated control., Accepted to the 2019 IEEE International Conference on Soft Robotics

Bubble lodgment in a complex capillary network is a common issue in many industrial and biological processes. Research work reported in the literature only investigated bubble dislodgment in single channels and did not consider the effect of network complexity on the dislodgment. This paper focuses on the pressure required to dislodge single bubbles from a microscopic capillary network and investigates the factors affecting the dislodging pressure to facilitate the precise control of bubble flows in porous media. A capillary network with multibifurcation and a smoothly changed diameter is designed to closely mimic the structure of the physiological vascular networks. Over 600 bubble dislodgment experiments have been conducted to understand the effect of the network structure, channel dimensions, and bubble length on the dislodging pressure. The results indicate that the network structure is a dominant factor affecting the dislodging pressure that increases with the increase in network complexity. The effect of bubble length on the dislodging pressure depends on the bubble length. When the bubble length is less than a certain value, which is around 2 mm in this study, the dislodging pressure increases significantly with the decrease of bubble length. When the bubble length is larger than 2 mm, the dislodging pressure is independent of the bubble length. A model has been proposed to explain the bubble dislodgment in complex capillary networks. The impact of the network structure on the bubble dislodging pressure is characterized by a parameter c j. The model indicates that the dislodging pressure is the function of bubble length, channel dimension, and network structure. The analysis of model parameters NB j and MA j shows that parameter c j, rather than the channel size, dominates the dislodging pressure for bubbles with a length greater than 2 mm, and the increase rate of the dislodging pressure is significantly affected by both channel size and parameter c j.

We are part of a growing community of researchers who are developing a new class of soft machines. By using mechanically soft materials (MPa Modulus) we can design systems which overcome the bulk-mechanical mismatches between soft biological systems and hard engineered components. To develop fully integrated soft machines—which include power, communications, and control sub-systems—the research community requires methods for interconnecting between soft and hard electronics.Sensors based upon eutectic gallium alloys in microfluidic channels can be used to measure normal and strain forces, but integrating these sensors into systems of heterogeneous Young’s Modulus is difficult due the complexity of finding a material which is electrically conductive, mechanically flexible, and stable over prolonged periods of time. Many existing gallium-based liquid alloy sensors are not mechanically or electrically robust, and have poor stability over time. We present the design and fabrication of a high-resolution pressure-sensor soft system that can transduce normal force into a digital output. In this soft system, which is built on a monolithic silicone substrate, a galinstan-based microfluidic pressure sensor is integrated with a flexible printed circuit board. We used conductive thread asinterconnect and found that this method alleviates problems arising due to the mechanical mismatch between conventional metal wires and soft or liquid materials.Conductive thread is low-cost, it is readily wetted by the liquid metal, it produces little bending moment into the microfluidic channel, and it can be connected directly onto the copper bond-pads of the flexible printed circuit board. We built a bridge-system to provide stable readings from the galinstan pressure sensor. This system gives linear measurement results between 500Pa-3500Pa of applied pressure.We anticipate that integrated systems of this type will find utility in soft-robotic systems as used for wearable technologies like virtual reality, or in soft-medical devices such as exoskeletal rehabilitation robots.