In recent years, implantable electronics, electronic skin (e‐skin), and flexible wearable devices have been developed due to their extensive applications in health monitoring, intelligent robots, and ...human disease treatment. Tactile sensors are the keys necessary to build skin‐inspired electronics. This article reviews the latest progress of e‐skin‐based flexible pressure sensors, such as piezoresistivity, capacitance, triboelectricity, and piezoelectricity from 2018 up to now. The working principles, structure design, active materials, and performance of numerous flexible pressure sensors are covered in detail. Finally, insights are provided and challenges and future perspectives of flexible pressure sensors in practical applications are discussed.
This article reviews the latest progress of electronic skin based flexible pressure sensors, such as piezoresistivity, capacitance, triboelectric, and piezoelectricity. The working principles, structure design, active materials, and performance of numerous flexible pressure sensors are covered in detail. Finally, insights are provided and challenges and future perspectives of flexible pressure sensors in practical applications are discussed.
Summary
There have been tremendous efforts made to investigate various materials to enhance the electrical performance of triboelectric nanogenerators (TENGs) but there is still demand for some ...techniques to further enhance the performance of tribomaterials. Therefore, we fabricated a bimetallic hybrid cryogel via cheap and facile UV‐radiation as well as in situ reduction method. Fabricated TENG device made up of porous hybrid bimetallic cryogel film containing silver and gold nanoparticles as tribopositive material and poly dimethyl siloxane (PDMS) as a tribonegative layer with dimension of 1 × 2 cm2 has the ability to produced output voltage of 262.14 V with current density of 27.52 mA/m2 and 7.44 W/m2 peak power density, which was sufficient to light up more than 120 white light emitting‐diodes (LEDs). Porous and rough structure, interaction of nanoparticles was the reason behind the performance enhancement of tribopositive material. Thus, this study introduces a very stable and easily synthesized bimetallic hybrid cryogel as a tribopositive material to enhance the performance of tribomaterials to design high performance TENG devices.
In this paper we investigated the effect of gold and silver nanoparticles inside the tribopositive porous cryogel for performance enhancement of TENG device. Silver nanoparticles have high contribution for performance enhancement as compared to gold. But with combination of both nanoparticles (Bimetallic cryogel) upon contact with tribonegative PDMS layer produces high power as compared to pure cryogel under the same external conditions.
Flexible electronics as an emerging technology has demonstrated potential for applications in various fields. With the advent of the Internet of Things era, countless flexible electronic systems need ...to be developed and deployed. However, materials and fabrication technologies are the key factors restricting the development and commercialization of flexible electronics. Here we report a simple, fast, and green flexible electronics preparation technology. The stencil printing method is adopted to pattern liquid metal on the thermoplastic polyurethane membrane prepared by electrospinning. Besides, with layer-by-layer assembly, flexible circuits, resistors, capacitors, inductors, and their composite devices can be prepared parametrically. Furthermore, these devices have good stretchability, air permeability, and stability, while they are multilayered and reconfigurable. As proof, this strategy is used to fabricate flexible displays, flexible sensors, and flexible filters. Finally, flexible electronic devices are also recycled and reconfigured.
The ongoing research for tribonegative materials has resulted in significant progress in triboelectric nanogenerators (TENG), but the search for tribopositive materials is limited. Therefore, it is ...still a challenging task to achieve low cost, readily available, easy process for fabrication of tribomaterials with high positive triboelectric properties for triboelectric nanogenerators. Here we propose a novel method to synthesize high porous cryogel films based on facile freezing, ultraviolet radiation and thawing processes and used it as the tribopositive material for TENG fabrication while spin-coated polydimethylsiloxane (PDMS) is used as the tribonegative material. The cryogel/PDMS TENG device with a dimension of 1 × 2 cm2 showed an open circuit voltage of 170 V, and a short circuit current density of 17.1 mA/m2 and an instantaneous power density of 2.95 W/m2 which is able to light up 180 white LEDs directly. Thorough investigations divulged that the high output performance of TENG can be attributed to the porous structure of the cryogel films and the formation of high-density mechanoradicals associated with the porous structure, which was proved by using radical scavanger 2,2,6,6-tetramethyl-1-piperidinyloxy. This study provides a simple, cost-effective and easy way of preparing cryogel films as the tribopositive material for TENGs, which increases the portfolio of tribopositive materials used for triboelectric nanogenerator with prodigious prospects.
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•A novel porous cryogel films based on facile freezing, UV radiation and thawing processes, has been proposed as the tribopositive material.•The output performance can be attributed to the porous structure and formation of mechanoradicals of Cr-3t18/PDMS TENGs.•The cryogel shows excellent thermal and mechanical stability.
Stretchable conductive yarns have received significant consideration in the direction of wearable and flexible electronics. Wearable electronic structures need strong materials to assure stability, ...durability, and an extensive range of strain to develop their applications. Therefore, manufacturing high-performance yarn-based devices with ultrarobustness and great stretchability with a simple, cost-effective, and scalable method remains a great challenge for wearable electronics. Here, a highly stretchable yarn with high performance is fabricated, which comprises a core TPU nanoyarn, successively decorated with a liquid metal (LM) layer, and a protective outer nanofiber layer. The ultrarobust (40 MPa) and high-strain (548%) conducting yarn presents potential applications in assembling strain sensors. Moreover, such a unique conductive yarn can be used as a highly deformable, stretchable conductor to charge a mobile phone or for data transfer, a sensor to monitor human activities, and as an effective control for a hand robot as well as for smart thermal management textile application. This research gives promising applications in the field of flexible and wearable electronics.
Stretchable electronics play a pivotal role in the age of information and intelligence. Integrated circuit components are an integral part of high-performance and multifunctional stretchable ...electronic devices. Therefore, it is an ideal design concept for stretchable electronic devices to not only ensure the reliability of the connection between rigid inorganic electronic components and stretchable circuits but also maintain the stretchability of the device. In this work, we constructed a mechanical gradient strategy to fabricate high-performance stretchable electronic devices. Briefly, polyvinyl alcohol glue is used to fix integrated circuits on stretchable circuits, which are fabricated by printing liquid metal on a thermoplastic polyurethane nanofiber membrane. The strategy of integrated circuits (rigid)-polyvinyl alcohol glue (high elastic modulus)-thermoplastic polyurethane nanofiber membrane (low elastic modulus)-liquid metal (liquid) realizes the strain gradient during the stretching process of the device, thus ensuring the stability and reliability. Moreover, we explored the mechanism through experiments and finite element analysis. The flexible electronic devices fabricated by this scheme are not only ultra-stretchable (900%) but also have good stability and comfort. As proof, the application in stretchable sensors, human-computer interaction devices, and displays was realized.
In recent years, tremendous efforts have been made to investigate tribomaterials for triboelectric nanogenerators (TENGs), but due to their low performance there is still need of tribomaterials with ...new mechanisms for performance enhancement. Therefore, in this study, the potential of conducting polyaniline and tribonegative graphene oxide is exploited for performance enhancement of tribopositive material through a new mechanism of disturbing the equilibrium state inside the tribopositive material under an impact force. Thus, a TENG device made up of polymer with 700 µL polyaniline and 4 mg mL−1 graphene oxide as tribopositive and polydimethylsiloxane as a tribonegative layer with a dimension of 1 × 2 cm2 is able to produce an open‐circuit voltage of 314.92 V and a current density of 37.81 mA m−2 with a peak power density of 10.43 W m−2, which can directly power ON more than 175 white light‐emitting diodes. Amine group of polyaniline and its pathway to mobilize electrons inside the tribopositive material due to electron accepting ability of graphene oxide upon physical contact under external force are the main contributing factors toward performance enhancement. This work introduces a low cost, easy fabrication process with a new method for performance enhancement of tribopositive material to acquire a high performance TENGs.
High performance triboelectric nanogenerators (TENGs) composed of polyaniline (PANI)–graphene oxide (GO) composite films are presented. Under the impact force, TENG generates high electrical output through an electron pathway mechanism made by GO and PANI inside a tribopositive material. This work explores a new insight mechanism to enhance the performance of TENG for high‐power application study.
With the rapid advances in wearable technology, several excellent strain sensors have been developed. Recent strain sensors have met various requirements, such as mechanical applicability, rapid ...responsiveness, and high sensitivity. Nevertheless, the processing technology, wearing comfort, and safety of strain sensors, which have received inadequate attention, have greatly hindered their commercial development and large‐scale use. Through mature electrospinning and screen‐printing, a high‐performance, safe, comfortable, waterproof, breathable, economical, and reliable wearable strain sensor is simply and quickly prepared. This strain sensor has excellent repeatability and stability with remarkable sensitivity (maximum gauge factor = 520), a broad working strain range (500%), and an ultrafast response time (100 ms). Notably, the mechanical properties of the proposed strain sensor are similar to those of natural skin, making the sensor a good match to the skin. Additionally, the strain sensor has incomparable biofriendly, enabling long‐term harmless contact with the skin. To the best of the authors’ knowledge, this is the first report on the optimization of flexible electronic equipment in terms of the manufacturing process, sensing performance, and wearing experience. The results of this study have important implications for the development and practical application of flexible electronics.
A safe and comfortable, waterproof and breathable, economical and reliable wearable strain sensor is simply and quickly prepared. The optimization of strain sensors in terms of preparation methods, sensing performance, and wearing experience is also realized. The results of this study have important implications for the commercialization and large‐scale manufacturing of wearable electronic equipment.
Wearable Strain Sensors
A safe and comfortable, waterproof and breathable, economical and reliable wearable strain sensor is simply and quickly prepared in article number 2200106 by Gang Zhao and ...co‐workers. The optimization of strain sensors in terms of preparation methods, sensing performance and wearing experience has also been realized, which is of great significance for the large‐scale manufacturing and commercialization of wearable devices.
