ICYS Annual Report 2023

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ICYS Annual Report 2023In the future envisioned by Society 5.0, the fusion of computers and robots through Human-Machine Interfaces (HMIs) is expected to extend beyond the limits of human capabilities. Stretchable sensing devices, seamlessly adherable to diverse surfaces including the human body, serve as an essential tool for HMI expansion. However, current stretchable devices lack a sustainable manufacturing platform, making mass production their functionality, challenging and significantly reliability, and device size. So far, conventional lithographic techniques have dominated the electronics manufacturing market due to their mature techniques, while the harsh and subtractive processes are hardly compatible with soft materials. This implies opportunities for us to undertake diversified studies of soft electronics manufacturing using additive processes to adapt for the application prospect. Liquid-mediated self-assembly has been demonstrated as one of the most promising alternatives to provide a simple, scalable and sustainable method for soft electronics manufacturing. This is because, unlike subtractive lithography, additive self-assembly sets up a spontaneous organization of solution-processable functional materials into desired structures on various substrates with high precision and efficiency.The research aims to establish a sustainable manufacturing platform aimed at implementing HMI, resolving the bottleneck impeding the practical application of stretchable devices. Patterns formed by one-dimensional material networks exhibit intrinsically exceptional elasticity, rendering them ideal for crafting stretchable devices. On the other hand, particle-free metal complex inks present promising prospects in the realm of soft device development. In pursuit of realizing Society 5.0, the research focuses on two primary topics: (A) Spontaneous patterning of stretchable devices for haptic human-machine interfaces; and (B) Metal complex ink for printed deformable sensors.(A) Spontaneous patterning of stretchable devices toward haptic human-machine interfacesStretchable polymers generally exhibit low surface free energy (γ=20-30 mJ/m2) due to high crosslinking degree, which makes it hard to generate the liquid-solid interaction and therefore In current study, a realize liquid-mediated patterning. counterintuitively charge-repulsive directed self-assembly technique is proposed for spontaneous patterning of stretchable circuits using AgNWs. Through generating strong repulsive force on the designated regions, the deposited AgNW ink gathers on the unmodified regions and results in AgNW circuits after room-temperature evaporation. These findings demonstrate that repulsive patterning enables precise control of 1D functional nanomaterials on stretchable substrates, marking a significant step forward in the sustainable development of stretchable devices and skin-integrated haptic interfaces (Fig. 1).Research Digest Lingying LI1. Outline of Research2. Research ActivitiesFig. 1. a Schematic of charge-repulsive patterning process and images of patterned AgNW circuits. b Skin-integrated strain sensor and signal processing algorithms for sensor data analytics.Fig. 2. a Schematic and photographs of formulated Ni complex inks. b Schematic illustration of the fabrication process of Ni patterns by screen printing and sintering. c Images of the patterned Ni circuits.References 1) W. Li et al., Applied Surface Science, 646,158967 (2024). 2) L. Li et al., Adv. Mater. Technol., 2101687 (2022). 3) L. Li et al., Small, 2101754 (2021).limiting (B) Metal complex ink for low-temperature printed electronicsThe development of low-temperature sintering Ni complex ink represents a significant advancement in printed electronics and soft devices owing to excellent electrical conductivity, corrosion resistance, and cost-effectiveness compared to noble metals. However, achieving efficient sintering at low temperatures remains a challenge due to the high energy barrier for Ni ion reduction and densification. Here, a hierarchical pyrolysis reduction strategy has been developed to produce Ni complex inks at low sintering temperature. We selected powdered Ni formate as a raw material because it can be reduced to metallic Ni by heating to about 250 °C. To realize low-temperature printed electronics, powdered material is required to form a reductive liquid state that can be printed. It is known that Ni ions, as a transition metal, can be coordinated by diversified ligands to form Ni complex ions with alterable properties. By formulating Ni-amine complex inks with tailored ligand reactions and reductive properties, a successive catalyzed reduction has been generated and thereby reduced Ni complex ink into continuous Ni nanoparticles circuits below 200 °C with ultrathin thickness and low resistivity (Fig. 2) 16Human Machine Interface based on Liquid-Mediated Self-Assembly