Stretchable and movable 3D structure is a great choice for sensing stretching and bending. This paper reports a novel cross-shaped 3D buckling strain sensor based on polydimethylsiloxane (PDMS) substrate for detecting stretching and bending. Using pre-stretched PDMS, cross-shaped Polyimide (PI) film with conductive silver paint on its top surface as a 2D precursor can pop up as a dynamic 3D structure and possesses capacitive effect and triboelectric effect under different stretching and bending, which can detect stretching directions, strain value, bending axis direction and radius of curvature simultaneously, showing great potential in human and robot applications.
This paper reports a novel self-powered three-dimension motion sensor capable of independently detecting contact trajectory, pressure and velocity based on triboelectrification and electrostatic induction synchronously. Motion trajectories in the full plane can be identified by using a unique net-cross electrodes configuration design. In addition, the patterned silver nanowires (AgNWs) electrodes are sprayed onto the polydimethylsilane (PDMS) substrate to achieve good transparency and stretchability. By attaching the 3D motion sensor on human skin or robot surface directly, the 3D motion information of the object could be acquired including pressure, velocity and trajectory. The self-powered 3D motion sensor is a promising candidate in terms of human-computer interaction, anti-counterfeiting signatures, etc.
In this paper, we present a scalable and general fabrication for micro-supercapacitors (MSCs) among various flexible substrates assisted by the stamp, which combines the conductive polymer composites with gravure printing process. Compared with the traditional transferring techniques, this method greatly simplifies the process and mitigates the mechanical damage during the preparation. Profiting from the composites of carbon nanotubes (CNTs) and polydimethylsiloxane (PDMS) as the printing inks, the MSCs exhibit elegant areal capacitance (10.491 μF/cm2) on the paper substrate. Meanwhile, optimizing the ratio of matrix and curing agent of PDMS, the interaction between ink and substrate is effectively enhanced. Therefore, such novel fabrication technology significantly improves the production efficiency as well as broadens the applications.
Wearable sweat sensors have the potential to provide continuous measurements of useful biomarkers. However, current sensors cannot accurately detect low analyte concentrations, lack multimodal sensing or are difficult to fabricate at large scale. We report an entirely laser-engraved sensor for simultaneous sweat sampling, chemical sensing and vital-sign monitoring. We demonstrate continuous detection of temperature, respiration rate and low concentrations of uric acid and tyrosine, analytes associated with diseases such as gout and metabolic disorders. We test the performance of the device in both physically trained and untrained subjects under exercise and after a protein-rich diet. We also evaluate its utility for gout monitoring in patients and healthy controls through a purine-rich meal challenge. Levels of uric acid in sweat were higher in patients with gout than in healthy individuals, and a similar trend was observed in serum.
Stretchable electronics have great importance in the application of wearable device and electronic skin. The balance and improvements of mechanical stretchability and electronic performance are the great challenges that restrict the further development of stretchable electronics. In order to achieve stretchable electronics, it is crucial to choose the proper substrates, among which PDMS is the most commonly used polymer due its easy fabrication and low cost. In this paper, we propose a novel strategy and fabricate localized and precise modulus-controlled PDMS for both two/three-dimensional stretchable electronics. Based on a secondary cross-link effect, the modulus of cured PDMS can be enhanced and precisely controlled by spin-coating different mass of curing agent. Using laser-cutted PI mask, the modulus-enhanced region can be defined by users. Through this simple method, the functional conductive thin-film materials (Gold/Ag nanowires/Reduced Graphene oxide) can be well protected when the structural layer is stretched and the “Barrel Effect” of multi-materials film (different material films possess different stretchability) on one piece of substrate can also be solved. Besides, the localizedly modified PDMS as a substrate can form different 3D buckling structures on it by pre-stretching and releasing process compared with uniform PDMS, which shows a new way to control the 3D buckling structure.
In response to the ongoing challenges for health care and human motion monitoring, this work proposes a three-electrode multi-module sensor (TEMS) integrating proximity feedback, compression sensing and stretching perception. With the assist of the porous carbon nanotubes (CNTs)-polydimethylsiloxane (PDMS) patch in optimized parameters, the unification of the device's out-of-plane non-contact sensing and in-plane contact segmental detection is realized. Besides, coordinated with a set of symmetrically patterned Ag nanowires (NWs) electrodes with specified initial conductivity, the device is highly-sensitive to two-dimensional strains and qualified for recognizing the horizontal tension strain as small as 0.077% and the vertical pressure exerted by a piece of scrip (0.18 Pa) in fast response (millisecond level). The anti-interference ability of the signals is ensured by the PDMS encapsulation and regional stiffness of the device. Furthermore, the simplified fabrication process based on PDMS doping/modification is suitable for human skin-attachable applications, especially as the accurate differentiation of similar motions and the time-phased judgment of continuous movements through collaboration among acquisition results.
Human skin is the largest organ, which covers the human body and provides us the mechanical stimuli to help us interact with the outer environment. Inspired from the properties of human skin, imitating of the complicated human sensation using stretchable electronic devices becomes one of the most exciting research fields due to its vast potential application fields like wearable electronics, healthcare monitoring and artificial intelligence. To mimic real human skin, the huge sensor network is required to attach the body, where it seems critical to guarantee the energy supply at the same time. Nowadays, the emerging triboelectric nanogenerator (TENG), which can transduce the mechanical energy into the electrical energy based on the contact electrification and electrostatic induction, provides an attractive solution for the energy problem to work as the self-powered sensor. The self-powered sensor can generate electrical signal by itself, responsing to the stimulation from the environment without further energy supply devices. With four fundamental working modes and three main detection modes, TENG could develop versatile configurations to realize the various kinds of sensation. The mechanical compliance and stretchability together with the electrical conductance can be fulfilled beneficial from the advancement of material and micro/nano fabrication technology. In this way, the TENG based self-powered electronic skins (e-skins) have been developed with rational design to accomplish multifunctions of sensing including the pressure, position, strain, sliding and so on. It is expected that the self-powered e-skin will continue its fast development and make more progress to make the e-skin come into human life in the near future.
The fast progressing electronic skins are spreading their applications into many aspects of human life. In terms of motion sensing, drawbacks exist in state-of-the-art approach of integrating sensing units into arrays e.g. the tradeoff between resolution and effective area, power consumption and interacting experience. This paper presents a novel self-powered digital-analog hybrid electronic skin for measuring noncontact linear planar displacement which achieves a high resolution of (0.75 mm, 1.07 mm, 2.20°) in a large area of 100 cm2 in three degrees of freedom. Owing to utilization of masked silver nanowires (AgNWs) spray coating and corona charging techniques in the fabrication process, this electronic skin is transparent and stretchable, while realizing self-powered sensing of an electret based on electrostatic inductions. Theory and localizing functions are proposed and proved by accordance with simulation and standard testing results. This electronic skin is capable of acting as an effective human-machine interface, which shows its future potential of practical usage in portable electronics, healthcare devices, and artificial intelligence, etc.
Triboelectric nanogenerator (TENG) harvesting living environmental energy has been demonstrated to be a potential energy source for internet of things, for its unique properties, such as high-output performance, clean, sustainability, low-cost etc., which have resulted in an explosive growth of related research in the past several years. However, due to the unique features of electrical output signals of TENGs like the pulsed output with random amplitude and frequency, ultra-high voltages and impedance, the electrical power generated by TENGs is hard to be delivered to the load efficiently or stored directly by the classical power management methods. Meanwhile, the mechanical energy from the environment is time dependent, unstable and sometime unpredictable, but the power required to drive electronics is regulated with a fixed input voltage and power. So it is important to store the generated energy in a battery or capacitor, so that it can be used to power a device sustainably. Fortunately, both the power management and energy storage for TENG have obtained significantly progress recently. Here, this paper reviews the progress made in power management and storage, including theoretical development, charge boosting, buck converting, energy storage, and the new enabled applications, aiming at building a self-charging power unit (SCPU) that can be a standard power package for sustainable operation of an electronic device. Finally, we will give an outlook for future development of applying SCPU for internet of things.
With wearable electronic devices arising, a flexible hybrid energy harvester that is capable to continuously harvest multi-types of energy and seamlessly integrate with human body draws great attentions. In this paper, we introduce a novel self-cleaning flexible hybrid energy harvesting system which includes a groove-shape micro/nanostructured haze thin film (GHF), a flexible power management circuit, and a hybrid energy harvester is integrated by a flexible organic solar cells (F-OSC) with an autonomous single-electrode triboelectric nanogenerator (AS-TENG) via one common-electrode. This system allows for simutaneously harvesting both solar and mechanical energy through two separate parts (i.e. the top F-OSC and the bottom AS-TENG). The flexible power management circuit simultaneously utilizes the large current of the solar cell and the high voltage of the TENG. In addition, GHF with excellent optical properties, large surface area and super-hydrophobicity has been introduced into the hybrid cell, which serves not only as a triboelectric layer to increase the surface charge density of the AS-TENG, but also as a light-trapping layer to improve the photoelectric conversion efficiency (PCE) of the F-OSC. Meanwhile, GHF helps this device to achieve unique functions, such as dust-proof, self-cleaning and self-encapsulating, which significantly improve the stability and repeatability of hybrid power unit in practical applications.
Abstract A novel pattern strategy of a nanomaterial network that can self-assemble onto prepatterned soft substrate to realize ultra-transparent electronics is presented. The approach detailed is based on the combination of nanomaterials' self-assembly at the water–air interface to form nanomaterial networks and the breakage phenomenon of water–nanomaterial membranes to form designed patterns. With the comprehensive investigation of this phenomenon, nanomaterial networks are manipulated to attach to prepatterned sidewalls. This leads to a remarkable transparency improvement without conductive property decline. Three 1D nanomaterials with various geometries are demonstrated to verify the universal feature of this pattern strategy, including silver nanowire (AgNW), carbon nanotube, and zinc oxide nanowire. Furthermore, sequential layer-by-layer deposition of several 1D nanomaterials has also been demonstrated by using the proposed approach, revealing an attractive potential of multiple-junction transparent electronics. The fabricated micro-grid structure of AgNWs with a line width of 5 µm and pitch of 150 µm has a sheet resistance of 37.88 Ω sq−1 and an optical transmittance of 86.06%. This fabrication strategy opens up opportunities for different nanomaterials in many transparent and wearable applications.
Sensors with multifunctions have attracted great attention for their extensive application value, among which humidity sensing and pressure sensing are necessary to electronics undoubtedly because of the complex physical environment we live in. Inspired by the structure of skin, in this article, we design a new method to combine wrinkle structure with porous sponge structure and achieve a novel, flexible, compressible, and bifunctional sensor based on carbon nanotube–polydimethylsiloxane (CNT–PDMS) with functions of humidity sensing and pressure sensing. The performance of the humidity sensing part can be controlled by the ultraviolet and ozone (UVO) treatment time and CNT concentration, while the sensitivity of the pressure sensing part can be controlled by the CNT concentration and grinding time of sugar granules. The bifunctional sensorcan easily sense approaching and touching of a hand, which shows great potential of alarming and protecting some electronics. Moreover, the bifunctional sensor can also be used in detecting human joint motions and breath conditions as a wearable and flexible health monitor.