Highly stretchable van der Waals thin films for adaptable and breathable electronic membranes

Abstract

The conformal integration of electronic systems with irregular, soft objects is essential for many emerging technologies. We report the design of van der Waals thin films consisting of staggered two-dimensional nanosheets with bond-free van der Waals interfaces. The films feature sliding and rotation degrees of freedom among the staggered nanosheets to ensure mechanical stretchability and malleability, as well as a percolating network of nanochannels to endow permeability and breathability. With an excellent mechanical match to soft biological tissues, the freestanding films can naturally adapt to local surface topographies and seamlessly merge with living organisms with highly conformal interfaces, rendering living organisms with electronic functions, including leaf-gate and skin-gate transistors. On-skin transistors allow high-fidelity monitoring and local amplification of skin potentials and electrophysiological signals.

MXene-Reinforced Liquid Metal/Polymer Fibers via Interface Engineering for Wearable Multifunctional Textiles

“…The apparent white smoke, produced by the reaction of hydrochloric acid and ammonia hydroxide, appeared above the textiles, which proves their high gas permeability due to the large pores between the textile fibers. Wearable textiles with hydrophilic surfaces can make the body more comfortable . Oxygen plasma treatment significantly improves the hydrophilicity of M 0.1 LM 5 S and compressed M 0.1 LM 5 S textiles, but has little effect on conductivity (Figure S31).…”

Inkjet printing of two-dimensional van der Waals materials: a new route towards emerging electronic device applications

“…Recently, spin-coating of electrochemically exfoliated vdW materials to obtain vdW layered films was found to be more suitable for depositing uniform 2D vdW films for flexible and stretchable applications than CVD growth of films because shear movement in the lateral direction is allowed due to the weak vdW interaction and network-like morphology, while the CVD-grown film cannot be freely stretched due to the strong in-plane covalent bonding between atoms. 109 This result indicates that a partially staggered structure of monolayer flakes can also be demonstrated by using inkjet printing to deliver stretchability while maintaining the unique properties of monolayer vdW materials. Although the bottom-up synthesis methods are known to produce lower quality 2D materials for the large-area applications so far, these methods can be alternatively used for the monolayer deposition if the remaining quality issue could be addressed, since they have attractive potentials, such as high controllability of surface morphology, crystallite size, and dopant.…”

Revisiting Solution-Based Processing of van der Waals Layered Materials for Electronics

“…As shown in Figure f, the vdW thin film exhibits conformal contact with the skin while it is repeatedly squeezed and stretched. As a result, the electrical signal of the thin film is stable under mechanical deformations, which further enables the implementation of thin-film devices for monitoring transient potentials such as cyclic eye closing and opening (Figure g) …”

“…Larger sizes and narrower thickness distributions become essential when the nanosheets form electronically active thin-film networks. As shown in the cross-sectional microscopic images, point and/or line contacts with interfacial disorder and noticeable energy barriers are dominant between liquid-phase exfoliated samples, while the E-MoS 2 nanosheets are clearly stacked by forming bonding-free vdW interfaces with a negligible energy barrier (Figures c,d). ,, Furthermore, the E-MoS 2 -based vdW thin films with broad-area sheet-to-sheet contacts are robust under various mechanical deformations, implying that solution-processed vdW layered materials are strong candidates for flexible and stretchable electronics …”

“…This can be attributed primarily to the high structural uniformity of the electrochemically exfoliated 2D individual nanosheets and the thin-film networks formed by vdW contacts. The effectively formed plane-to-plane contacts in thin-film networks allow mechanical stability under local tension or compression without losing conductive pathways . This remarkable mechanical stability enables the extension of 2D vdW thin-film-based electronics into bioelectronic applications through integration with soft objects such as human skin and leaves.…”