Polyelectrolyte elastomer-based ionotronic sensors with multi-mode sensing capabilities via multi-material 3D printing.

Stretchable ionotronics have drawn increasing attention during the past decade, enabling myriad applications in engineering and biomedicine. However, existing ionotronic sensors suffer from limited sensing capabilities due to simple device structures and poor stability due to the leakage of ingredients. In this study, we rationally design and fabricate a plethora of architected leakage-free ionotronic sensors with multi-mode sensing capabilities, using DLP-based 3D printing and a polyelectrolyte elastomer. We synthesize a photo-polymerizable ionic monomer for the polyelectrolyte elastomer, which is stretchable, transparent, ionically conductive, thermally stable, and leakage-resistant. The printed sensors possess robust interfaces and extraordinary long-term stability. The multi-material 3D printing allows high flexibility in structural design, enabling the sensing of tension, compression, shear, and torsion, with on-demand tailorable sensitivities through elaborate programming of device architectures. Furthermore, we fabricate integrated ionotronic sensors that can perceive different mechanical stimuli simultaneously without mutual signal interferences. We demonstrate a sensing kit consisting of four shear sensors and one compressive sensor, and connect it to a remote-control system that is programmed to wirelessly control the flight of a drone. Multi-material 3D printing of leakage-free polyelectrolyte elastomers paves new avenues for manufacturing stretchable ionotronics by resolving the deficiencies of stability and functionalities simultaneously.

Encapsulating eutectogels for stretchable humidity-resistant strain sensors.

Eutectogels are stretchable ionic conductors extensively developed in recent years, owing to their distinct advantages of low cost, non-volatility, non-toxicity, and outstanding biocompatibility. However, the susceptibility to humidity caused by the exchange of water molecules between the interiors of eutectogels and the external environment greatly restricts their practical applications. Here, a dip-coating strategy is proposed to fabricate a P(MEA-co-IBA) elastomer-coated P(AAC-co-AAM) eutectogel to achieve satisfactory humidity-resistant capability. The hydrophobic elastomer coating significantly suppresses water exchange without harming the stretchability (>500%) and conductivity of the eutectogel. Strong adhesion forms at the eutectogel-coating interface due to the formation of an interpenetrating layer. The superior electromechanical performances of encapsulated eutectogels enable stretchable ionotronic devices with stable electrical performance (>1 h) and remarkable water-droplet/moist resistances during static/dynamic loadings. A humidity-resistant encapsulated eutectogel-based wearable strain sensor is further demonstrated. The proposed humidity-resistant eutectogels are promising candidates for soft and wearable ionotronics for practical applications.

Progress of Hydrophobic Ionogels: A Review.

The emergence of hydrophobic ionogels composed of hydrophobic polymer matrices and hydrophobic ionic liquids has drastically broadened the applications of ionic devices, especially for underwater explorations. Compared with traditional ionogels, hydrophobic ones are capable of achieving long-term stability in ambient and aqueous environments. In this review, the latest research developments of intrinsically hydrophobic ionogels are summarized, with particular emphases placed on the materials, mechanisms and applications. The basic issues about hydrophobic ionogels, including the material systems, dynamic gelation bonds and network structures are elucidated. The up-to-date advent of the ambient/underwater applications of hydrophobic ionogels concerning adhesion, self-healing, and sensing are comprehensively summarized. Special attention is paid to underwater scenarios considering the rapid development of marine explorations and the intrinsic properties of hydrophobic ionogels. Finally, the current challenges and immediate opportunities of this emerging yet fast-developing research field are discussed.

Data storage and encryption with a high security level based on molecular configurational isomers.

Developing advanced materials for highly secure data-encryption is crucial but very challenging, as most data-encryption materials (the message area) are chemically different from the substrates (the background) on which they are being written, leading to high risks of data leakage by deciphering via sophisticated instrumental analysis. Additionally, most materials require only one stimulus for decryption, resulting in a low-level of data-security. Here, a three configurational isomer-based data-encryption method is developed (i.e., propylamine, isopropylamine, and cyclopropylamine). Their similar molecular formulae, elemental constitution, and physiochemical properties make them ideal date-encryption materials. On the other hand, the significant differences in lower critical solution temperatures (LCST) of the corresponding polyacrylamides, i.e., 10 °C for poly(N-propylacrylamide), 32 °C for poly(N-isopropylacrylamide), and 53 °C for poly(N-cyclopropylacrylamide), respectively, render an effective method for data decryption. Relying on the above features, the data written by three isomers are well-hidden under given conditions. And a specific temperature range, rather than a simple temperature increase or decrease, would be required for decryption. Furthermore, undesired temperatures give wrong outputs, which is highly deceptive to the hacker. Therefore, a high-level of data security can be achieved. This result opens a new door for designing advanced materials for improving the data-security level.

A Camel Nose-Inspired Highly Durable Neuromorphic Humidity Sensor with Water Source Locating Capability.

Numerous emerging applications in modern society require humidity sensors that are not only sensitive and specific but also durable and intelligent. However, conventional humidity sensors do not have all of these simultaneously because they require very different or even contradictory design principles. Here, inspired by camel noses, we develop a porous zwitterionic capacitive humidity sensor. Relying on the synergistic effect of a porous structure and good chemical and thermal stabilities of hygroscopic zwitterions, this sensor simultaneously exhibits high sensitivity, discriminability, excellent durability, and, in particular, the highest respond speed among reported capacitive humidity sensors, with demonstrated applications in the fast discrimination between fresh, stale, and dry leaves, high-resolution touchless human-machine interactive input devices, and the real-time monitoring humidity level of a hot industrial exhaust. More importantly, this sensor exhibits typical synapse behaviors such as paired-pulse facilitation due to the strong binding interactions between water and zwitterions. This leads to learning and forgetting features with a tunable memory, thus giving the sensor artificial intelligence and enabling the location of water sources. This work offers a general design principle expected to be applied to develop other high-performance biochemical sensors and the next-generation intelligent sensors with much broader applications.