Skin electronics require stretchable conductors that satisfy metallike conductivity, high stretchability, ultrathin thickness, and facile patternability, but achieving these characteristics simultaneously is challenging. We present a float assembly method to fabricate a nanomembrane that meets all these requirements. The method enables a compact assembly of nanomaterials at the water–oil interface and their partial embedment in an ultrathin elastomer membrane, which can distribute the applied strain in the elastomer membrane and thus lead to a high elasticity even with the high loading of the nanomaterials. Furthermore, the structure allows cold welding and bilayer stacking, resulting in high conductivity. These properties are preserved even after high-resolution patterning by using photolithography. A multifunctional epidermal sensor array can be fabricated with the patterned nanomembranes.

Hydrogels consist of a cross-linked porous polymer network and water molecules occupying the interspace between the polymer chains. Therefore, hydrogels are soft and moisturized, with mechanical structures and physical properties similar to those of human tissue. Such hydrogels have a potential to turn the microscale gap between wearable devices and human skin into a tissue-like space. Here, we present material and device strategies to form a tissue-like, quasi-solid interface between wearable bioelectronics and human skin. The key material is an ultrathin type of functionalized hydrogel that shows unusual features of high mass-permeability and low impedance. The functionalized hydrogel acted as a liquid electrolyte on the skin and formed an extremely conformal and low-impedance interface for wearable electrochemical biosensors and electrical stimulators. Furthermore, its porous structure and ultrathin thickness facilitated the efficient transport of target molecules through the interface. Therefore, this functionalized hydrogel can maximize the performance of various wearable bioelectronics.

Two dimensional (2D) materials have found various applications because of their unique physical properties. For example, graphene has been used as the electron transparent membrane for liquid cell transmission electron microscopy (TEM) due to its high mechanical strength and flexibility, single-atom thickness, chemical inertness, etc. Here, we report using 2D MoS2 as a functional substrate as well as the membrane window for liquid cell TEM, which is enabled by our facile and polymer-free MoS2 transfer process. This provides the opportunity to investigate the growth of Pt nanocrystals on MoS2 substrates, which elucidates the formation mechanisms of such heterostructured 2D materials. We find that Pt nanocrystals formed in MoS2 liquid cells have a strong tendency to align their crystal lattice with that of MoS2, suggesting a van der Waals epitaxial relationship. Importantly, we can study its impact on the kinetics of the nanocrystal formation. The development of MoS2 liquid cells will allow further study of various liquid phenomena on MoS2, and the polymer-free MoS2 transfer process will be implemented in a wide range of applications.

Wearable electronic devices are used to perform various electronic functions on the human skin, and their mechanical softness while maintaining high performances is critical. Therefore, there is a need to develop novel materials with outstanding softness and high electrical and ionic conductivity for wearable electronics. Here, we present an intrinsically stretchable and conductive nanocomposite based on alginate hydrogels and silver nanowires (AgNWs). The developed nanocomposite was applied to highly conductive soft electrodes that can be used in various wearable electronic devices. The nanocomposite electrode was prepared by cross-linking alginate molecules in the presence of AgNWs, exhibiting higher electrical, ionic conductivity, higher stretchability, and lower modulus than conventional conducting rubbers. By forming a bilayer structure with the nanocomposite and the ultrasoft hydrogel layer, the mechanical properties of the nanocomposite device could be matched to that of the human skin. We used the nanocomposite electrode for fabricating key device components of wearable electronics, such as a wearable antenna and a skin-mountable supercapacitor. Such demonstrations successfully proved the effectiveness of the proposed nanocomposite as a soft conducting material for wearable electronics.

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YKL-40 is up-regulated in mild and moderate/severe persistent allergic rhinitis, and its expression can be regulated differentially by different cytokines, possibly contributing to the remodeling of nasal mucosa in allergic rhinitis.

Stretchable electrodes, which are essential components of nextgeneration electronic devices, should be highly conductive under multiaxial tensile strain, durable under repetitive stretching, and patternable for integrating stretchable devices. Herein, a lubricant-added stretchable conductive composite of a polydimethylsiloxane-based elastomer containing silver flakes is reported. The added lubricant minimizes changes in conductivity during stretching and maximizes elastic durability by reducing friction. The conductivity varies from 1933.3 S•cm −1 at 0% strain to 307.5 S• cm −1 at 300% uniaxial stretching and 1264.1 S•cm −1 at 50% biaxial stretching. Furthermore, the composite exhibits high durability, even after 1000 cycles of stretching at 200%, and the conductive composite paste can be applied to fine-linewidth direct writing.

To develop highly sensitive flexible pressure sensors, the mechanical and piezoresistive properties of conductive thermoplastic materials produced via additive manufacturing technology were investigated. Multi-walled carbon nanotubes (MWCNTs) dispersed in thermoplastic polyurethane (TPU), which is flexible and pliable, were used to form filaments. Specimens of the MWCNT/TPU composite with various MWCNT concentrations were printed using fused deposition modelling. Uniaxial tensile tests were conducted, while the mechanical and piezoresistive properties of the MWCNT/TPU composites were measured. To predict the piezoresistive behaviour of the composites, a microscale 3D resistance network model was developed. In addition, a continuum piezoresistive model was proposed for large-scale simulations.