Rubbery electronics and sensors from intrinsically stretchable elastomeric composites of semiconductors and conductors

A general strategy to impart mechanical stretchability to stretchable electronics involves engineering materials into special architectures to accommodate or eliminate the mechanical strain in nonstretchable electronic materials while stretched. We introduce an all solution-processed type of electronics and sensors that are rubbery and intrinsically stretchable as an outcome from all the elastomeric materials in percolated composite formats with P3HT-NFs [poly(3-hexylthiophene-2,5-diyl) nanofibrils] and AuNP-AgNW (Au nanoparticles with conformally coated silver nanowires) in PDMS (polydimethylsiloxane). The fabricated thin-film transistors retain their electrical performances by more than 55% upon 50% stretching and exhibit one of the highest P3HT-based field-effect mobilities of 1.4 cm2/V.s, owing to crystallinity improvement. Rubbery sensors, which include strain, pressure, and temperature sensors, show reliable sensing capabilities and are exploited as smart skins that enable gesture translation for sign language alphabet and haptic sensing for robotics to illustrate one of the applications of the sensors

Harnessing Deep Learning of Point Clouds for Inverse Control of 3D Shape Morphing

Shape-morphing devices, a crucial branch in soft robotics, hold significant application value in areas like human-machine interfaces, biomimetic robotics, and tools for interacting with biological systems. To achieve three-dimensional (3D) programmable shape morphing (PSM), the deployment of array-based actuators is essential. However, a critical knowledge gap impeding the development of 3D PSM is the challenge of controlling the complex systems formed by these soft actuator arrays. This study introduces a novel approach, for the first time, representing the configuration of shape morphing devices using point cloud data and employing deep learning to map these configurations to control inputs. We propose Shape Morphing Net (SMNet), a method that realizes the regression from point cloud data to high-dimensional continuous vectors. Applied to previous 2D PSM actuator arrays, SMNet significantly enhances control precision from 82.23% to 97.68%. Further, we extend its application to 3D PSM devices with three different actuator mechanisms, demonstrating the universal applicability of SMNet to the control of 3D shape morphing technologies. In our demonstrations, we confirm the efficacy of inverse control, where 3D PSM devices successfully replicate target shapes. These shapes are obtained either through 3D scanning of physical objects or via 3D modeling software. The results show that within the deformable range of 3D PSM devices, accurate reproduction of the desired shapes is achievable. The findings of this research represent a substantial advancement in soft robotics, particularly for applications demanding intricate 3D shape transformations, and establish a foundational framework for future developments in the field

Entirely flexible on-site conditioned magnetic sensorics

The first entirely flexible integrated magnetic field sensor system is realized consisting of a flexible giant magnetoresistive bridge on-site conditioned using high-performance IGZO-based readout electronics. The system outperforms commercial fully integrated rigid magnetic sensors by at least one order of magnitude, whereas all components stay fully functional when bend to a radius of 5 mm

Wearable high-performance pressure sensors based on three-dimensional electrospun conductive nanofibers

Polymer-based pressure sensors play a key role in realizing lightweight and inexpensive wearable devices for healthcare and environmental monitoring systems. Here, conductive core/shell polymer nanofibers composed of poly (vinylidene fluoride-co-hexafluoropropene) (PVDF-HFP)/poly(3,4-ethylenedioxythiophene) (PEDOT) are fabricated using three-dimensional (3D) electrospinning and vapor deposition polymerization methods, and the resulting sponge-like 3D membranes are used to create piezoresistive-type pressure sensors. Interestingly, the PEDOT shell consists of well-dispersed spherical bumps, leading to the formation of a hierarchical conductive surface that enhances the sensitivity to external pressure. The sponge-like 3D mats exhibit a much higher pressure sensitivity than the conventional electrospun 2D mats due to their enhanced porosity and pressure-tunable contact area. Furthermore, large-area, wireless, 16 x 10 multiarray pressure sensors for the spatiotemporal mapping of multiple pressure points and wearable bands for monitoring blood pressure have been fabricated from these 3D mats. To the best of our knowledge, this is the first report of the fabrication of electrospun 3D membranes with nanoscopically engineered fibers that can detect changes in external pressure with high sensitivity. The developed method opens a new route to the mass production of polymer-based pressure sensors with high mechanical durability, which creates additional possibilities for the development of human-machine interfaces.11Ysciescopu

A Flexible PMN-PT Ribbon-Based Piezoelectric-Pyroelectric Hybrid Generator for Human-Activity Energy Harvesting and Monitoring

The rapid advancements of wearable electronics require continued innovation in sustainable power sources and human interactive sensors. An abundance of energy in various forms, such as mechanical, thermal, optical, and sound, are ubiquitous in the environment and human activities. Hybrid generators using piezoelectric polymers with relatively low piezoelectric and pyroelectric constants have been fabricated to simultaneously scavenge mechanical and thermal energies. In this work, micropatterned single-crystal (1-x)Pb(Mg,Nb)O3-xPbTiO3 (PMN-PT) ribbons, which possess excellent piezoelectric and pyroelectric properties, are utilized to build human activities energy harvesting and monitoring systems. The flexible PMN-PT ribbon-based sensor conformally attached on the surface of human skin enables high sensitivity for human body motions and can detect acoustic sounds precisely. The sensor has been used for monitoring temperature-related activities, caused for instance by warm water flow and even light illumination. The multifunctional performance of the PMN-PT ribbon-based hybrid generator shows great potential for self-powered wearable and human activities monitoring devices. This is the peer reviewed version of the following article: Chen, Y. et al.: A Flexible PMN-PT Ribbon-Based Piezoelectric-Pyroelectric Hybrid Generator for Human-Activity Energy Harvesting and Monitoring. In: Advanced Electronic Materials (2017), which has been published in final form at http://onlinelibrary.wiley.com/doi/10.1002/aelm.201600540/abstract. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.DFG/DI 2013/2-1BMBF/Q.Com-H/16KIS010

A stretchable and biodegradable strain and pressure sensor for orthopaedic application

The ability to monitor, in real time, the mechanical forces on tendons after surgical repair could allow personalized rehabilitation programmes to be developed for recovering patients. However, the development of devices capable of such measurements has been hindered by the strict requirements of biocompatible materials and the need for sensors with satisfactory performance. Here we report an implantable pressure and strain sensor made entirely of biodegradable materials. The sensor is designed to degrade after its useful lifetime, eliminating the need for a second surgery to remove the device. It can measure strain and pressure independently using two vertically isolated sensors capable of discriminating strain as small as 0.4% and the pressure exerted by a grain of salt (12 Pa), without them interfering with one another. The device has minimal hysteresis, a response time in the millisecond range, and an excellent cycling stability for strain and pressure sensing, respectively. We have incorporated a biodegradable elastomer optimized to improve the strain cycling performances by 54%. An in vivo study shows that the sensor exhibits excellent biocompatibility and function in a rat model, illustrating the potential applicability of the device to the real-time monitoring of tendon healing

Continuous wireless pressure monitoring and mapping with ultra-small passive sensors for health monitoring and critical care

Continuous monitoring of internal physiological parameters is essential for critical care patients, but currently can only be practically achieved via tethered solutions. Here we report a wireless, real-time pressure monitoring system with passive, flexible, millimetre-scale sensors, scaled down to unprecedented dimensions of 1 × 1 × 0.1 cubic millimeters. This level of dimensional scaling is enabled by novel sensor design and detection schemes, which overcome the operating frequency limits of traditional strategies and exhibit insensitivity to lossy tissue environments. We demonstrate the use of this system to capture human pulse waveforms wirelessly in real time as well as to monitor in vivo intracranial pressure continuously in proof-of-concept mice studies using sensors down to 2.5 × 2.5 × 0.1 cubic millimeters. We further introduce printable wireless sensor arrays and show their use in real-time spatial pressure mapping. Looking forward, this technology has broader applications in continuous wireless monitoring of multiple physiological parameters for biomedical research and patient care.Nature Communications 5, 5028. (2014)2041-17232041-173

Self-curing super-stretchable polymer/microgel complex coacervate gels without covalent bond formation

Elastic physical gels are highly desirable because they can be conveniently prepared and readily shaped. Unfortunately, many elastic physical gels prepared in water require in situ free-radical polymerization during the gel formation stage. In contrast, complex coacervate gels are physical gels that can be prepared by simply mixing two pre-formed oppositely-charged polyelectrolytes. However, as far as we are aware, highly elastic complex coacervate gels have not yet been reported. Herein, we combine polyanionic microgel particles with a well-known commercially-available cationic polyelectrolyte to prepare polymer/microgel complex coacervate (PMCC) physical gels. This new family of gels requires annealing at only 37 °C and behaves like a covalent gel but does not form covalent bonds. Thermal reconfiguration of the dynamic ionic bonds transforms the shapeable pre-gel into a highly elastic gel that is super-stretchable, adhesive, self-healing, highly swellable and can be further toughened using Ca2+ as an ionic crosslinker. Our PMCC gels have excellent potential for applications as engineering gels and structural biomaterials, as well as for wound healing and water purification

Air/water interfacial assembled rubbery semiconducting nanofilm for fully rubbery integrated electronics

A rubber-like stretchable semiconductor with high carrier mobility is the most important yet challenging material for constructing rubbery electronics and circuits with mechanical softness and stretchability at both microscopic (material) and macroscopic (structural) levels for many emerging applications. However, the development of such a rubbery semiconductor is still nascent. Here, we report the scalable manufacturing of high-performance stretchable semiconducting nanofilms and the development of fully rubbery transistors, integrated electronics, and functional devices. The rubbery semiconductor is assembled into a freestanding binary-phased composite nanofilm based on the air/water interfacial assembly method. Fully rubbery transistors and integrated electronics, including logic gates and an active matrix, were developed, and their electrical performances were retained even when stretched by 50%. An elastic smart skin for multiplexed spatiotemporal mapping of physical pressing and a medical robotic hand equipped with rubbery multifunctional electronic skin was developed to show the applications of fully rubbery-integrated functional devices