E‐waste is rapidly turning into another man‐made disaster. It is proposed that a paradigm shift toward a more sustainable future can be made through soft‐matter electronics that are resilient, repairable if damaged, and recyclable (3R), provided that they achieve the same level of maturity as industrial electronics. This includes high‐resolution patterning, multilayer implementation, microchip integration, and automated fabrication. Herein, a novel architecture of materials and methods for microchip‐integrated condensed soft‐matter 3R electronics is demonstrated. The 3R function is enabled by a biphasic liquid metal‐based composite, a block copolymer with nonpermanent physical crosslinks, and an electrochemical technique for material recycling. In addition, an autonomous laser‐patterning method for scalable circuit patterning with an exceptional resolution of <30 µm in seconds is developed. The phase‐shifting property of the BCPs is utilized for vapor‐assisted “soldering” circuit repairing and recycling. The process is performed entirely at room temperature, thereby opening the door for a wide range of heat‐sensitive and biodegradable polymers for the next generation of green electronics. The implementation and recycling of sophisticated skin‐mounted patches with embedded sensors, electrodes, antennas, and microchips that build a digital fingerprint of the human electrophysiological signals is demonstrated by collecting mechanical, electrical, optical, and thermal data from the epidermis.

No abstract

Printed soft conductive materials for stretchable electronics should have low electrical resistivity, high strain limit, and stable electrical properties when stretched. Previously, it has been shown that a bi‐phasic ink composed of silver (Ag) microflakes, eutectic gallium−indium (EGaIn) alloy, and styrene isoprene (SIS) block copolymer is a promising formulation for printed soft electronics and has the potential to satisfy the necessary criteria. In this study, further improvements to the ink formulation are explored, with a focus on how the choice of Ag microflakes affects the electrical and electromechanical properties of the composite. By using specific Ag microflakes, AgInGa‐SIS inks that have conductivity as high as 6.38 × 105 S m−1 and a strain limit of over 1000%, with low electromechanical coupling can be synthesized. More broadly, when comparing the composite with different silver flakes, there is a 176% relative difference in conductivity, >600% difference in strain limit, and 277% relative difference in electromechanical coupling. To demonstrate the applicability of these inks for various use cases such as wearable bioelectronics, interconnects are printed for connecting electronic breakout boards with microcontrollers that provide a stable electrical connection when stretched, and the interconnects and electrodes of a wearable electrocardiography system that monitors the heart pulses in real‐time.

No abstract

This work addresses two well-known problems of tissue-interfacing hydrogels, that is, rapid drying and skin adhesion. These are considered as the main barriers against the wider application of hydrogels in many fields, including wearable bioelectronics. We demonstrate for the first time a hydrogel with a double solvent that is softer than the skin (compression Young’s modulus = 3.6 kPa), yet highly stretchable (>500%), nondrying, skin-adhering, with a skin–electrode impedance lower than the gold-standard Ag/AgCl electrodes, skin-friendly, and transparent. This combination of properties has not been demonstrated before but is necessary for widespread use of hydrogel electrodes. Various formulations of the double-network glycerol–polyacrylamide hydrogel are fully characterized in order to enhance skin adhesion, softness, liquid content retention, and signal-to-noise ratio. We then demonstrate a double-layer stretchable e-textile architecture, which embeds a large number of these electrodes, as a multinode gateway for high-resolution bidirectional data exchange between the body and bioelectronics and show proof-of-concept applications in functional neuromuscular electrostimulation of the forearm and wearable monitoring of brain, heart, and facial expressions.

A novel architecture of materials and fabrication techniques is proposed that serves as a universal method for implementation of thin-film biostickers for high resolution electrophysiological monitoring. Unlike the existing wearable patches, the presented solution can be worn for several days, and is not affected by daily routines such as physical exercise or taking bath. A printable biphasic liquid metal silver composite is used, both as the electrical interconnects and the electrodes. This allows combining advantages of dry electrodes, i.e., printability and non-smearing behavior, with benefits of wet electrodes, i.e., high-quality signal. A human subject study showed that these biphasic printed electrodes benefit from a lower electrode-skin impedance compared to clinical grade Ag/AgCl electrodes. Digital printing enables autonomous fabrication of biostickers that are taylor-made for each user and each application. A universal miniaturized electronic system for biopotential acquisition and wireless communication is develpoed, and demonstrated multiple biopotential acquisition cases, including electrocardiography, electroencephalography, electromyography, and electrooculography.

Dielectric elastomer actuators (DEAs) are popular in soft robotics, [1,2] millirobotics, [3] microfluidics, [4] and haptics [5] due to their low current consumption, [6] high actuation strains, [7] fast response times, [8] and intrinsically high mechanical compliance that arises from their soft material architecture.DEAs are based on a relatively simple capacitor-like stacked multilayer structure in which a dielectric elastomer film is coated with thin layers of soft conductive material. [6] The compliance, material integrity, and conductivity of these surface electrodes strongly influence the performance of DEAs. In particular, these electrodes should be highly stretchable and have a low stiffness to minimize mechanical resistance to elastic deformation and work output induced by electromechanical coupling. Carbon grease (CG) is commonly used as an electrode material because it is soft, stretchable, and can be easily deposited as a thin coating. CG is a paste-like mixture of carbon black (CB) particles and silicon oil that does not dry out and has minimal resistance to high strain actuation. However, because it is a fluid, CG electrodes can be difficult to pattern with high resolution, and they easily smear and create smudge marks on contacting objects during actuation, rendering the DEA unusable. [9] Studies reported in the literature also suggest that the oil in the grease may penetrate the dielectric membrane, leading to premature electrical breakdown. [10] CB powder can be deposited directly on the dielectric film and can be used on its own as the electrode. However, in the absence of a binder medium or carrier fluid, the carbon powder can redistribute over the course of repeated actuation cycles, resulting in regions with insufficient conductivity to transfer charge or induce electromechanical coupling, resulting in lower strains. [9] As with CG, CB electrodes are also susceptible to smearing. To address this, soft elastomers such as polydimethylsiloxane (PDMS) are often used as a binder medium to disperse CB. [11] However, these particle-filled conductive elastomers suffer from unstable electromechanical properties over time, [12,13] i.e., they become less conductive and require a long time to recover the original conductivity. In addition, their stiffness contributes to greater resistance to actuation and mechanical work output. [11] Metallic thin films have also been proposed as a solution for the creation of DEA electrodes. [14] Although metallic films are highly conductive and do not smear, they are too stiff, having a negative impact on the actuation performance of the actuator. Also, ionically conductive hydrogels enabled the creation of fully transparent compliant electrodes, [15,16] yet, at such high voltages (kV), electrolysis occurs. [17] Recently, carbon nanotubes (CNTs) were presented as an alternative for fabricating ultrathin, highly conductive DEA electrodes that add no stiffness to the dielectric and can easily be integrated with multilayer actuators. [3,18,19] Yet, the early onset of diele...

No abstract