Electronic devices and systems with high stretchability are essential in the fields of wearable electronics, on-skin electronics, soft robotics, and bioelectronics. Stretchable electronic devices conventionally built with elastomeric thin films show a lack of permeability, which not only impedes wearing comfort and creates skin inflammation over long-term wearing, but also limits the design form factors of device integration in the vertical direction. Here we report a new type of stretchable conductor, namely liquid metal fiber mat (LMFM), which is fabricated by simple coating or printing of liquid metal on electrospun elastomeric fiber mat. Liquid metal hanging among the elastomeric fibers self-organizes into the laterally mesh-like and vertically buckled structure, which simultaneously offers high perm eability, stretchability, conductivity, and electrical stability. Besides, LMFM shows smart adaptiveness to omnidirectional stretching over 1800% strain and good biocompatibility. We demonstrate the use of LMFM as the building block to realize highly permeable and multifunctional monolithic stretchable electronics.

Liquid metal (LM) has recently been used as an advanced stretchable material for constructing stretchable and wearable electronics. However, due to the poor wettability of LM and the large dimensional change during stretching, it remains very challenging to obtain a high conductivity with minimum resistance increase over large tensile strains. To address the challenge, an LM‐superlyophilic and stretchable fibrous thin‐film scaffold is reported, on which LM can be readily coated or printed to form permeable superelastic conductors. In contrast to conventional LM‐based conductors where LM particles are filled into an elastic matrix or printed on the surface of an elastic thin film, the LM can quickly infuse into the LM‐superlyophilic scaffold and form bi‐continuous phases. The LM‐superlyophilic scaffold shows unprecedented advantages of an extremely high uptake of the LM and a conductivity‐enhancement characteristic when stretched. As a result, the LM‐based conductor displays and ultrahigh conductivity of 155 900 S cm−1 and a marginal resistance change by only 2.5 fold at 2 500% strain. The conductor also possesses a remarkable durability over a period of 220 000 cycles of stretching tests. The printing of LM onto the LM‐superlyophilic scaffold for the fabrication of various permeable and wearable electronic devices is demonstrated.

high-performance batteries as the fundamental constituent of the e-textiles. [9] Existing coin and pouch types of batteries remain the most widely used options nowadays, but their fixed shapes and rigidity largely hinder the seamless integration into different wearable formats, particularly those require high levels of deformation and wearing comfort. [10] Wire-type batteries appear to be promising candidates to address this challenge because the omnidirectional flexibility offered by the wire shape can effectively withstand complicated mechanical deformations, and the resemblance of the shape to slender fibers and yarns of textiles allows for the easy integration into wearable formats via mature textile technologies, such as braiding, weaving, and knitting. [11] To date, only a few studies of wiretype batteries have been reported in the literature, most of which are developed on the basis of lithium-ion battery (LIB) and zinc-ion battery (ZIB) chemistries. Nevertheless, due to the low theoretical capacity and the low mass loading of the anode materials, the energy densities of those wire-type LIBs and ZIBs are low (5-160 Wh L −1 ). [12][13][14][15][16][17][18][19] Recent studies on lithium (Li)-metal anode have suggested that wire-type Li-metal batteries (LMBs) may meet the energy demand because of the remarkable theoretical capacity and the lowest electrochemical potential of Li. [20] However, those reports only made use of bulky and thick Li-metal wires (LMWs) in their study, which adversely resulted in two major disadvantages. Electrochemically, LMWs showed a short cyclic life (3-100 cycles) owing to the formation of Li dendrites, and the largely oversized Li-metal led to the low energy density of the battery (2-70 Wh L −1 ). [21][22][23][24] Mechanically, LMWs could easily undergo plastic deformation because of its low yield strength (<1 MPa), which significantly limited the flexing stability of the wire-type battery. [25,26] It is noted that, in the literature studies of flexible LMBs, the cycling stability and flexibility of Li-metal anodes can be substantially enhanced by depositing the Li-metal on a flexible host. However, these studies adopted the reactive wetting process for the fabrication of Li-metal composites, which required the use of Li-reactive materials. [27][28][29][30][31][32] On the one hand, the molten Li must react with oxides or form new alloys with reactive metals before it can wet the hosts. Such vigorous chemical High-capacity and omnidirectionally flexible wire-type lithium (Li)-metal batteries represent a feasible technology for the realization of electronic textiles. However, the use of commercially available Li-metal wires as anodes nowadays confronts many electrochemical and mechanical issues such as dendrite formation, low yield strength, and poor fatigue resistance. Here, a flexible and stable Li-metal composite yarn (LMCY) is designed via a fast capillary filling of molten Li into metallic carbon yarn for fabricating high-energy-density and long-lasting wire-type Li-metal batte...

Implantable bioelectronics provide unprecedented opportunities for real-time and continuous monitoring of physiological signals of living bodies. Most bioelectronics adopt thin-film substrates such as polyimide and polydimethylsiloxane that exhibit high levels of flexibility and stretchability. However, the low permeability and relatively high modulus of these thin films hamper the long-term biocompatibility. In contrast, devices fabricated on porous substrates show the advantages of high permeability but suffer from low patterning density. Here, we report a wafer-scale patternable strategy for the high-resolution fabrication of supersoft, stretchable, and permeable liquid metal microelectrodes (μLMEs). We demonstrate 2-μm patterning capability, or an ultrahigh density of ~75,500 electrodes/cm 2 , of μLME arrays on a wafer-size (diameter, 100 mm) elastic fiber mat by photolithography. We implant the μLME array as a neural interface for high spatiotemporal mapping and intervention of electrocorticography signals of living rats. The implanted μLMEs have chronic biocompatibility over a period of eight months.

Skin Electronics Provides Remarkable Opportunities for Non‐Invasive And Long‐Term Monitoring of A Wide Variety of Biophysical And Physiological Signals that Are Closely Related to Health, Medicine, And Human‐Machine Interactions. Nevertheless, Conventional Skin Electronics Fabricated on Elastic Thin Films Are Difficult to Adapt to The Wet Microenvironments of The Skin: Elastic Thin Films Are Non‐Permeable, Which Blocks The Skin Perspiration; Elastic Thin Films Are Difficult to Adhere to Wet Skins; Most Skin Electronics Are Difficult to Work Underwater. Here, We Report A Wet‐Adaptive Electronic Skin (WADE‐skin), Which Consists of A Next‐To‐Skin Wet‐Adhesive Fibrous Layer, A Next‐To‐Air Waterproof Fibrous Layer, And A Stretchable And Permeable Liquid Metal Electrode Layer. While The Electronic Functionality Is Determined by The Electrode Design, This WADE‐skin Simultaneously Offers Superb Stretchability, Wet Adhesion, Permeability, Biocompatibility, And Waterproof Property. The WADE‐skin Can Rapidly Adhere to Human Skin After Contact for A Few Seconds And Stably Maintain The Adhesion Over Weeks Even Under Wet Conditions, Without Showing Any Negative Effect to The Skin Health. We Demonstrate The Use of WADE‐skin for The Stable Recording of Electrocardiogram During Intensive Sweating as Well as Underwater Activities, And as The Strain Sensor for The Underwater Operation of Virtual Reality‐Mediated Human‐Machine Interactions.This article is protected by copyright. All rights reserved