Self-healable printed magnetic field sensors using alternating magnetic fields

Room-Temperature Organic Spintronic Devices with Wide Range Magnetocurrent Tuning and Multifunctionality via Electro-Optical Compensation Strategy

In spintronics, devices exhibiting large, widely tunable magnetocurrent (MC) values at room temperature are particularly appealing due to their potential in advanced sensing, data storage, and multifunctional technologies. Organic semiconductors (OSCs), with their rich and unique spin-dependent and (opto-)electronic properties, hold significant promise for realizing such devices. However, current organic devices are constrained by limited design strategies, yielding MC values typically confined to tens of percent, thereby restricting their potential for multifunctional applications. Here, this study introduces an electro-optical compensation strategy to modulate MC values, which synergistically integrates and manages the interplays among carrier transport, spin-dependent reactions, and photogenerated carrier dynamics in OSCs-based devices. This approach achieves ultrahigh room-temperature MC values of +13 200% and -10 600% in the designed devices, with continuous and precise tunability over this range-marking a breakthrough in organic spintronic devices. Building on this achievement, by integrating multiple controllable parameters-light, bias, magnetic field, and mechanical flexibility-into a single device, a flexible, room-temperature, multifunctional device is activated, functioning as the high-sensitivity magnetic field sensor, composite field sensor, magnetic current inverter, and magnetically-controlled artificial synaptic, etc. These findings open an avenue for designing high-performance, multifunctional devices with broad implications for future spintronic-related technologies.

Responsive Magnetic Polymer Nanocomposites through Thermal-Induced Structural Reorganization

Polymer nanocomposites (PNCs), which feature a hybrid network of soft polymers filled with nanoparticles, hold promise for application in soft robots due to their tunable physiochemical properties. Under certain environmental conditions, PNCs undergo stimuli-responsive structural rearrangement and transform the energy of the ambient environment into diverse uses, for example, repairing the injuries and reconfiguring the shapes of the materials. We develop PNCs with the ability of thermal-responsive restructuring by the stepwise assembly of functional components, including magnetite nanoparticles, silylated cellulose, and polydimethylsiloxane. We investigate the dynamic changes of the nano- and submicron structure of the magnetic PNCs upon the stimulation of heating based on a combined analytical approach: using dynamic mechanical analysis to interpret the viscoelastic properties of the PNC and in situ small-angle X-ray scattering to quantify the clustering of NPs. Based on these results, we formulate a structural model for the heating-induced evolution of the nano- to submicrometer assemblies in the magnetic PNC. Moreover, thermal-induced restructuring of magnetic PNCs leads to additional favorable functions, such as the abilities of healing, welding, reprocessing, and responses to photo and magneto stimuli. Our design provides a versatile means to develop responsive PNCs for applications in soft robots, sensors, and actuators.

Scalable magnetoreceptive e-skin for energy-efficient high-resolution interaction towards undisturbed extended reality

Electronic skins (e-skins) seek to go beyond the natural human perception, e.g., by creating magnetoperception to sense and interact with omnipresent magnetic fields. However, realizing magnetoreceptive e-skin with spatially continuous sensing over large areas is challenging due to increase in power consumption with increasing sensing resolution. Here, by incorporating the giant magnetoresistance effect and electrical resistance tomography, we achieve continuous sensing of magnetic fields across an area of 120 × 120 mm2 with a sensing resolution of better than 1 mm. Our approach enables magnetoreceptors with three orders of magnitude less energy consumption compared to state-of-the-art transistor-based magnetosensitive matrices. A simplified circuit configuration results in optical transparency, mechanical compliance, and vapor/liquid permeability, consequently permitting its imperceptible integration onto skins. Ultimately, these achievements pave the way for exceptional applications, including magnetoreceptive e-skin capable of undisturbed recognition of fine-grained gesture and a magnetoreceptive contact lens permitting touchless interaction.

Omnidirectionally Stretchable Spin-Valve Sensor Array with Stable Giant Magnetoresistance Performance

Flexible magnetic sensors, which have advantages such as deformability, vector field sensing, and noncontact detection, are an important branch of flexible electronics and have significant applications in fields such as magnetosensitive electronic skin. Human skin surfaces have complicated deformations, which pose a demand for magnetic sensors that can withstand omnidirectional strain while maintaining stable performance. However, existing flexible magnetic sensor arrays can only withstand stretching along specific directions and are prone to failure under complicated deformations. Here, we demonstrate an omnidirectionally stretchable spin-valve sensor array with high stretchability and excellent performance. By integrating the modulus-distributed structure with liquid metal, the sensor can maintain its performance under complex deformations, enabling the overall system with omnidirectional stretchability. The fabricated spin-valve sensor exhibits a nearly unchanged giant magnetoresistance ratio of 8% and a maximum sensitivity of 0.93%/Oe upon omnidirectional strain up to 86% and can maintain stable performance without fatigue for over 1000 stretching cycles. Furthermore, this spin-valve sensor array is characterized by stable sensing performance for magnetic fields under complicated deformations and can be applied as a magnetosensitive electronic skin. Our results provide insights into the development of next-generation stretchable and wearable magnetoelectronics.

3D-Printable Elastomers for Real-Time Autonomous Self-Healing in Soft Devices

Photocurable self-healing elastomers are promising candidates for producing complex soft devices that can mend damage. However, the practicality of these materials is limited by reliance on external stimuli, custom synthesis, manual realignment, and multihour healing cycles. This paper introduces a tough 3D-printable hybrid acrylate/thiol-ene elastomer (prepared with commercially available precursors) that exhibits nearly instantaneous damage repair in the absence of external stimuli. This rapid, hydrogen bond-driven self-healing enables meaningful restoration of mechanical properties, including tensile strains up to 344% post-damage. Furthermore, structured herringbone grafts are showcased as a compelling strategy to enable cohesive failure away from healed interfaces, realizing up to 18× increases in toughness from only modest increases in interfacial surface area. Prototype soft robotic devices fabricated using vat photopolymerization demonstrate self-healing within seconds under ambient conditions and without external intervention. These results demonstrate a scalable strategy to provide real-time, autonomous functionality restoration in damaged soft devices.

Printed magnetoresistive sensors for recyclable magnetoelectronics

We have developed an innovative recyclable printed magnetoresistive sensor using GMR microflakes and AMR microparticles as functional fillers, with PECH as the elastomer binder. Under saturation magnetic fields of 100 mT and 30 mT, these sensors respectively exhibit magnetoresistance values of 4.7% and 0.45%. The excellent mechanical properties and thermal stability of the PECH elastomer binder endow these sensors with outstanding flexibility and temperature stability. This flexibility, low cost, and scalability make these sensors highly suitable for integration into flexible electronic devices, such as smart security systems and home automation. Moreover, these sensors are fully recyclable and reusable, allowing the materials to be separated, reused, and remanufactured without loss of performance. The low energy consumption of the production process and the recyclability of the materials significantly reduce the environmental impact of these magnetic field sensors.

Advances in Flexible Magnetosensitive Materials and Devices for Wearable Electronics

Emerging fields, such as wearable electronics, digital healthcare, the Internet of Things, and humanoid robots, highlight the need for flexible devices capable of recording signals on curved surfaces and soft objects. In particular, flexible magnetosensitive devices garner significant attention owing to their ability to combine the advantages of flexible electronics and magnetoelectronic devices, such as reshaping capability, conformability, contactless sensing, and navigation capability. Several key challenges must be addressed to develop well-functional flexible magnetic devices. These include determining how to make magnetic materials flexible and even elastic, understanding how the physical properties of magnetic films change under external strain and stress, and designing and constructing flexible magnetosensitive devices. In recent years, significant progress is made in addressing these challenges. This study aims to provide a timely and comprehensive overview of the most recent developments in flexible magnetosensitive devices. This includes discussions on the fabrications and mechanical regulations of flexible magnetic materials, the principles and performances of flexible magnetic sensors, and their applications for wearable electronics. In addition, future development trends and challenges in this field are discussed.

Photon-Dipole-Spin Interactions in M(TCNE)x/P(VDF-TrFE) Multiferroic Heterostructure Available for Bimodal Control of Multistate Data-Storage

Organic multiferroic heterostructure is one of the most promising structures for the future design of high-density flexible energy-efficient data storage. Here, organic ferromagnetic metal(tetracyanoethylene) (M(TCNE))x/ferroelectric poly(vinylidene fluoride-co-trifluoroethylene) (P(VDF-TrFE)) multiferroic heterostructures are fabricated, where the excited state in M(TCNE)x interacted with localized dipole in P(VDF-TrFE) provides a key link for the interfacial coupling. Thus, aligned dipoles in P(VDF-TrFE) by external electric field can affect the magnetization of Fe(TCNE)x effectively to result in a pronounced magnetization-voltage (M-V) hysteresis loop. Moreover, light-induced electron-hole pairs in Fe(TCNE)x with long lifetime effectively interact with the dipoles in P(VDF-TrFE) to lead to an effect in external light control of electric polarization of P(VDF-TrFE). Overall, the organic multiferroic heterostructure provides the possibility of realizing two storage modes, light control of dipole as well as electric field control of spin, which can broaden multifunctional applications of organic multiferroic materials in the area of multistate storage.

Design and Development of Transient Sensing Devices for Healthcare Applications

With the ever-growing requirements in the healthcare sector aimed at personalized diagnostics and treatment, continuous and real-time monitoring of relevant parameters is gaining significant traction. In many applications, health status monitoring may be carried out by dedicated wearable or implantable sensing devices only within a defined period and followed by sensor removal without additional risks for the patient. At the same time, disposal of the increasing number of conventional portable electronic devices with short life cycles raises serious environmental concerns due to the dangerous accumulation of electronic and chemical waste. An attractive solution to address these complex and contradictory demands is offered by biodegradable sensing devices. Such devices may be able to perform required tests within a programmed period and then disappear by safe resorption in the body or harmless degradation in the environment. This work critically assesses the design and development concepts related to biodegradable and bioresorbable sensors for healthcare applications. Different aspects are comprehensively addressed, from fundamental material properties and sensing principles to application-tailored designs, fabrication techniques, and device implementations. The emerging approaches spanning the last 5 years are emphasized and a broad insight into the most important challenges and future perspectives of biodegradable sensors in healthcare are provided.

Towards high performance and durable soft tactile actuators

Soft actuators are gaining significant attention due to their ability to provide realistic tactile sensations in various applications. However, their soft nature makes them vulnerable to damage from external factors, limiting actuation stability and device lifespan. The susceptibility to damage becomes higher with these actuators often in direct contact with their surroundings to generate tactile feedback. Upon onset of damage, the stability or repeatability of the device will be undermined. Eventually, when complete failure occurs, these actuators are disposed of, accumulating waste and driving the consumption of natural resources. This emphasizes the need to enhance the durability of soft tactile actuators for continued operation. This review presents the principles of tactile feedback of actuators, followed by a discussion of the mechanisms, advancements, and challenges faced by soft tactile actuators to realize high actuation performance, categorized by their driving stimuli. Diverse approaches to achieve durability are evaluated, including self-healing, damage resistance, self-cleaning, and temperature stability for soft actuators. In these sections, current challenges and potential material designs are identified, paving the way for developing durable soft tactile actuators.