Omnidirectional printing of elastic conductors for three-dimensional stretchable electronics

Abstract

Printing solid-state elastic conductors into self-supporting three-dimensional (3D) geometries promises the design diversity of soft electronics, enabling complex, multifunctional, and tailored human-machine interfaces. However, the di culties in manipulating their rheological characteristics have only allowed for layerwise deposition. Here, we report omnidirectional printing of elastic conductors enabled by emulsifying elastomer composites with immiscible, nonvolatile solvents. The strategy simultaneously achieves superior viscoelastic properties that provide the structural integrity of printed features, and pseudoplastic and lubrication behaviours that allow great printing stability. Freestanding, lamentary, and out-of-plane 3D geometries of intrinsically stretchable conductors are directly written, achieving a minimum feature size <100 μm and excellent stretchability >150%. Particularly, the evaporation of the continuous phase in the emulsion results in microstructured, surface-localized conductive networks, signi cantly improving their electrical conductivity. To illustrate the feasibility of our approach, we demonstrate skin-mountable electronics that visualize temperature on a matrix-type stretchable display based on omnidirectionally printed elastic interconnects. Full TextSkin electronics augment the capability of shareable signals from personal and metabolic activities over communication networks by blurring the physical discontinuity between electronic devices and human skin [1][2][3][4] . With their unique mechanical characteristics, such as lightweight design, softness, and stretchability, skin electronics can be functionalized on various body parts 5,6 and even brains 7 and hearts 8 in the forms of biosensors, processors, and displays. For high-delity operation under these challenging circumstances, the design of skin electronics needs to be tailored elaborately to individuals 9,10 . However, traditional mask-based lithography primarily optimized for the mass production of standardized, uniform electronics cannot effectively deal with the morphological diversity of the human bodies. Moreover, existing manufacturing processes still lack strategies to implement threedimensional (3D) structures with soft functional materials such as vertical interconnect accesses (VIAs) and multilayer circuitries that are crucial to the realization of high-performance, multifunctional applications.Printing electrical wirings into 3D structures could be a promising solution for maximizing the customizability of skin electronics and achieving circuit complexity. However, most conventional 3D printing processes still deposit one layer at a time, which is unsuitable for complex, lamentary, and omnidirectional wirings (including a z-directional component). Alternatively, viscoelastic inks that simultaneously exhibit high quasi-static stiffness and strong shear-thinning behaviour can immediately solidify after extrusion from a nozzle-based printhead, allowing direct writing of self-supporting 3D structures [11][12][13][14][15...

Omnidirectional Printing of PEDOT:PSS for High-Conductivity Spanning Structures

“…Due to high G ′ and τ y , the ink was desired to be printed vertically. − Vertical printing involved three steps (Figure a) for fabricating micropillars with a substantial length-to-diameter ratio. Initially, the nozzle descended until it came into contact with the substrate.…”

Pressure-Activatable Liquid Metal Composites Flexible Sensor with Antifouling and Drag Reduction Functional Surface

“…Currently, there are various methods for preparing sensors, and additive manufacturing has gained significant attention due to its high accuracy and relatively low cost. − One of these methods is direct ink writing (DIW), which has the advantage of being highly adjustable in terms of material, allowing for the printing of customized inks as required. − The viscosity of the ink is typically adjusted using solid thickeners, photosensitive coupling agents, or other means to make it suitable for printing. − Integrated soft electronics can be produced by printing a mixture of different inks in a controlled manner. For instance, combining conductive and dielectric elastomeric inks in an additive manufacturing platform can create soft electronics. , However, current integrated sensors do not consider the impact of the external environment on their service life in specific usage scenarios.…”

Topology-Mediated Molecule Nucleation Anchoring Enables Inkjet Printing of Organic Semiconducting Single Crystals for High-Performance Printed Electronics

“…Printed electronics offer fantastic opportunities to create large-area electronic systems by means of high-throughput, low-cost, and low-carbon-footprint printing technologies. , The significant development of various materials and printing approaches over the past decade has led to the implementation of printed circuitry with improved electrical performance. − Nevertheless, organic semiconducting thin films deposited via solution printing generally suffer from abundant grain boundaries and trap states, − severely hampering their application in advanced printed electronics. Organic semiconducting single crystals (OSSCs) possess extraordinary electronic and optoelectronic properties in terms of high mobility, long exciton diffusion length, and high optical gain due to low defect density and absence of grain boundaries. ,− They are ideal candidates for creating functional printed devices with high performance.…”

“…Printed electronics offer fantastic opportunities to create largearea electronic systems by means of high-throughput, low-cost, and low-carbon-footprint printing technologies. 1,2 The significant development of various materials and printing approaches over the past decade has led to the implementation of printed circuitry with improved electrical performance. 1−6 Nevertheless, organic semiconducting thin films deposited via solution printing generally suffer from abundant grain boundaries and trap states, 4−6 severely hampering their application in advanced printed electronics.…”