Search

The emergence of cutting‐edge cross‐disciplines has motivated the rapid development of wearable technology and flexible electronics. The flexibility and tunable properties of organic materials enable organic flexible electronics to adapt to complex surface deformations and achieve sensitive detection of physiological signals. The cost‐effectiveness of organic materials in mass production offers additional possibilities for the practical and commercialization of e‐skin technology. However, how to ensure stability and long‐term reliability while maintaining a highly sensitive, flexible, and stretchable is a challenge for e‐skins. In this review, the research progress and development trend of e‐skin is systematically summarized, especially the latest breakthroughs and innovations in the frontier of organic flexible electronics, and systematically review the applications of e‐skin in sensors, physiological monitoring, and energy supply. In addition, the review further discusses the prospects and current challenges for the application of organic flexible electronics in e‐skin, which provides a one‐stop reference for the development of e‐skin. [ABSTRACT FROM AUTHOR]

Silk fibroin (SF) is a biodegradable protein and possesses superior skin‐friendliness, biocompatibility, low immunogenicity, and non‐toxicity. However, SF has a series of drawbacks. For example, the application of SF in water filtration is limited by its inadequate ability to adsorb heavy metal ions. It is not inherently antibacterial, making SF ineffective as a filter to eliminate airborne bacteria. SF without conductivity is not suitable for use in sensors and triboelectric nanogenerators. In tissue engineering, deficient mechanical and anti‐inflammatory properties also have an influence on the rate of wound recovery. While physical and chemical modifications will improve its application properties as well as broaden its application areas. This review describes the modification of SF by filling, blending, structural adjustment, post treatment, crosslinking, grafting, and in situ polymerization to provide it with other functional properties. Modified SF fibers prepared by various methods (e.g., wet/dry/microfluidic spinning, electrospinning) are discussed, and they can be used in water/air filtration, chemical/pressure/strain sensors, triboelectric nanogenerators, artificial skin, wound dressings, and tissue scaffolds. Finally, the development trend of the modified SF fibers is prospected. This review has a reference significance on how to use modified SF fibers to improve filtration efficiency, sensor performance, and wound recovery. [ABSTRACT FROM AUTHOR]

Performance degradation and even loss of function due to mechanical stiffening caused by internal water evaporation and/or freezing significantly limit the application of hydrogel‐based electronics. Herein, a high‐performance liquid‐free electronic skin (e‐skin) is assembled based on the dry poly(ethylene glycol)‐based gel and conductive Ti3C2 MXenes that is successfully applied in wearable strain sensors. The fabricated liquid‐free e‐skin exhibits superior mechanical performance, broad sensing ranges (>1000%), good temperature adaptability, and durable environmental stability. Without extra sealed packaging, the e‐skin sensor maintains remarkable cycling stability and retains 98.5% conductivity at room temperature after 6 months. Furthermore, the liquid‐free e‐skin sensors are utilized to provide individuals with proper guidance on body alignment and posture awareness, fostering the development and maintenance of correct exercise techniques, thus mitigating the likelihood of sports‐related injuries. This work provides a novel liquid‐free electron‐conductive electronic integrated with adhesiveness, stretchability, self‐healabilitiy, and antifreezing, which can meet wide application needs from artificial skins to smart interfaces. [ABSTRACT FROM AUTHOR]

3D printing (3DP) is an accessible platform being increasingly utilized by independent researchers in fields ranging from industrial manufacturing to medicine. 3D bioprinting is a form of 3D printing that makes use of "bioinks," organic or synthetic polymer formulations that are often laden with cells. The wide range of materials available means that bioinks can be tailored to the types of tissue that they are meant to emulate. Human skin has a complex microenvironment consisting of numerous layers, cell types, growth factors, and molecular signaling pathways. 3D bioprinting's flexibility and ability to create complex, bioactive structures means that it has great potential in creating artificial skin constructs for skin wound regeneration. While the available materials and cell types for 3DP are large, an ideal bioink for printing artificial skin remains yet to be found. This review will cover the various types of 3DP, the bioinks commonly used, the functionalization of printed artificial skin constructs, challenges that arise in the 3D bioprinting of skin, and future directions for the field. The structure of skin and the wound healing process will also be discussed, as sufficient understanding of these subjects is key to the development of therapeutic artificial skin constructs. [ABSTRACT FROM AUTHOR]

The pH sensing devices can provide important health information with applications in infection detection, disease diagnosis, and personalized medicine. However, these devices are often expensive with modest flexibility and require bulky readout instruments, thus inappropriate for wearable, remote, and continuous health monitoring applications. Herein, an integrated, miniaturized, modular, wearable, battery-free, biocompatible, flexible, 3D-printed (WB2F3D) sensor system for on-demand, continuous, wireless, and real-time pH monitoring is proposed, developed, and fully characterized. The 3D-printing of nanomaterials on skin-like flexible substrates is innovatively applied to enable multimaterial and multilayer printing of the sensors, reusable electronic/communication circuity, and antennas in a tailorable, lowcost, and time-efficient manner. The battery-free and flexible readout system is designed to enable wireless and on-demand energy and data transmission for continuous and real-time pH monitoring. This sensor system exhibits high sensitivity (≈|51.76| mV pH-1), specificity, repeatability, reproducibility toward various pH ranges (3.0-10.0), excellent mechanical flexibility, and outstanding biocompatibility (cell viability > = 90%). It successfully demonstrates the pH change monitoring in an ex situ hydrogel-based wound model. The WB2F3D sensor system is envisioned to provide an integrated platform for accurate, on-demand, battery-free, wireless, and real-time human health monitoring, and another step toward personalized medicine. [ABSTRACT FROM AUTHOR]

The development of low‐cost accessible technologies for rapid prototyping of mechanical components has democratised engineering tools for hobbyists and researchers alike. The development of analogous approaches to fabrication of soft‐matter, and biologically compatible materials containing living cells, is anticipated to be similarly enabling across multiple fields of biological research. LEGO toy construction bricks represent low‐cost, precision engineered, and versatile construction materials for rapid prototyping. This study demonstrates construction of a benchtop LEGO 3D bioprinter for additive layer manufacture of a 3D structure containing viable human skin cells within a hydrogel scaffold. 3D bioprinted structures are formed from the deposition of microfluidically generated bio‐ink droplets containing live keratinocyte skin cells, representing components toward an artificial skin model. Fluid flow rates and printer speed, together with bio‐ink gelation rate, determine droplet packing arrangement in the bioprinted structures. The printing of 3D structures containing multiple bio‐inks is demonstrated and live cells are imaged in the resulting bioprints. Fluid delivery can be achieved using LEGO pumps and readily available, or home‐3D‐printed, microfluidic components, therefore avoiding the need for any specialist microfluidic hardware. Build instructions are described to enable easy uptake, modification and improvement by other laboratories, as well provide an accessible platform for learning and education. Affordable, accessible, and easy to use tools for 3D bioprinting are anticipated to open opportunities for a greater number of research labs to work with 3D cell culture and bio‐printed materials, with bioprinting expected to assist in better understanding of disease, contribute to tissue engineering and repair, and enable personalised medicine through the printing of cultured patient cells. The presented approach is not only an easily accessible laboratory tool for bioprinting, but also provides a learning system for mechanical construction, robotics, coding, microfluidics and cell biology, making it a versatile platform for research, education, and science engagement. [ABSTRACT FROM AUTHOR]

Electronic skin (E‐skin), especially the wearable sensors efficiently detect various stimuli attracted huge research interest owing to their potential applications in health monitoring and artificial intelligence. On the other hand, functional polymer composites possessing excellent properties such as light weight, good flexibility, and superior electrical performances, are promising candidates as building blocks for flexible electronics. Accordingly, tremendous efforts are devoted to the development of polymer composites with functional properties for E‐skin applications. Here, recent advances on the controlled fabrication of various fillers based functional polymer composites and their diverse applications in E‐skin are reviewed. In addition, contemporary studies on fabrication strategies, working mechanisms, and device performance for E‐skin based on the functional polymer composites are reviewed, including flexible pressure sensors, strain sensors, temperature sensors, energy harvesters, and transistors. Furthermore, the applications of functional composite based flexible electronics in healthcare and artificial intelligence are discussed. Finally, the existing challenges and opportunities for the functional composite materials based E‐skin are summarized. [ABSTRACT FROM AUTHOR]

Electronic skin (e‐skin) is facing new challenges owing to the development of artificial intelligence. Among the existing working modes, triboelectric‐based e‐skin (TES) can convert mechanical energy into electrical energy and can be used as a sensor to directly output an electrical signal without additional power supply. Therefore, with the advantages of self‐powering, low cost, and wide application of materials, TES provides a new concept for developing e‐skin and has been extensively studied. Starting from TES, this review describes the working principle and application of triboelectric nanogenerators (TENGs) in e‐skin. Existing materials for TES can be mainly divided into fiber textiles, gels, liquid‐based materials, and degradable materials. Therefore, the material section is divided into four chapters to describe the properties of each material. As for the structure of TES, the transition from single‐channel to multi‐channel for the multifunctionalization of TES is described, and the various links required for a TES‐based closed‐loop system are introduced. Based on these advanced units, the recent progress as well as the current challenges and future development prospects of TES are reviewed. [ABSTRACT FROM AUTHOR]

User‐interactive interfaces, converting tactile stimuli into readable signals to users and devices simultaneously, improve the communication and interaction between human and machines and therefore greatly contribute to the safety and dexterity during the interactions. However, the concomitant challenges of current user‐interactive interfaces such as complex architecture, massive electrodes and fussy cable connections, bulky and unhandy power supply, and deficiency in multistimuli responses have yet to be solved. Herein, an all‐optical tactile sensing platform consisting of heterogeneous mechanoluminescent materials and polymer matrix is proposed for the conversion of multiple tactile stimuli into heterochromatic lights in an untethered and self‐powered manner. The all‐optical tactile sensing platform can respond to tiny shear force such as fingertip slipping with a low limit of 2 N and wide range of strains ranging from 30% to 70% with appropriate discrimination. Most importantly, the visualization of tactile stimuli with human‐ and machine‐readability and vividness permit remote and wireless user‐interactive applications such as videogames and RC car control, assisted with the developed method of active optical signal recognition. This work presents a paradigm shift to user‐interactive interfaces, boosting their implementation in multitudinous areas such as artificial intelligences and the Internet of Things. [ABSTRACT FROM AUTHOR]

With increasingly diverse functionalities of electronic skins (E‐skins), components and structures for the E‐skin have also become more diverse and complex. It is extremely challenging to make all the components and devices required for additional functionalities stretchable and breathable to ensure skin comfort. Herein, we report a facile strategy to realize a versatile hybrid E‐skin patch with great skin comfort by developing a breathable and stretchable metastructure to serve as the platform material of the hybrid E‐skin patch. A Kagome‐based mechanical metastructure made of breathable, stretchable medical adhesive integrates and tethers non‐stretchable or stiff components and devices to the skin, allowing for both the breathability and mechanical comfort of skin. A wireless skin sensor system to sense electrocardiogram (ECG) signals and wirelessly transmit ECG signals in an event‐driven manner such as sending R peaks only is developed on a polyimide‐based flexible printed circuit board. The Kagome metastructure‐tethered wireless ECG sensor patch does not cause significant skin discomfort when worn for five days, and successfully enables the event‐driven wireless monitoring of ECG signals. We envision that this facile and versatile approach expands the type of materials and functionalities of E‐skin for digital healthcare, personalized medicine, and smart prosthetics with emerging functionalities. [ABSTRACT FROM AUTHOR]

Electronic skin (E‐skin) is widely used in bionic prosthesis, soft robotics, and wearable electronic devices. Waterproof and breathable membranes that provide a high level of protection and comfort are promising core materials for meeting the pressing demand for E‐skin. However, creating such materials exhibiting waterproofness, breathability, and ease of fabrication has proven to be a great challenge. In this paper, waterproof, breathable Modal‐based knitted fabric E‐skin is proposed by using a simple, low‐cost three‐step process including the graphene oxide (GO) loading, GO‐reducing, and polydimethylsiloxane loading. The prepared E‐skin is insensitive to common liquids in daily life including water, tea, milk, and coffee, showing superior waterproof capability. The breathability is also tested with a water vapor transmission rate of ≈13.6 mg cm−2 h−1. Besides, this E‐skin can achieve reliable human motion monitoring. The authors believe this E‐skin can provide a reliable principle for further design and development of waterproof and breathable electronic skin. [ABSTRACT FROM AUTHOR]

Piezoelectric sensors and energy harvesters have received considerable interest due to their self‐powered capability and potential applications in various electronic devices. However, it is still a challenge to fabricate stretchable piezoelectric devices because piezoelectrics mainly consists of stiff crystalline structures. Here, extremely stretchable and tough piezoelectric gels are reported, which are prepared simply by swelling poly(ethylene glycol) (PEG)‐based poly(urethane‐urea) (PUU) gels with aqueous solution of molecular ferroelectrics. The hydrogen interactions between the PEG segments in the gels and the molecular ferroelectrics (dabcoHReO4, DH) enable well dispersion and crystallization of DH in the PEG segments. The resulted PUU/DH composite piezoelectric gels exhibit unique tensile mechanical properties, including superior strain (>1000%), high breaking strength (>10 MPa), modulus (>2 MPa), and toughness (>57 MJ cm−3). The extremely stretchable and tough piezoelectric gels show excellent piezoelectric properties (d33 ≈ 62 pC N−1 for films with a 10 wt% of DH and light transparency (>90%), and can quantitatively detect different mechanical deformations. Additionally, the energy generators can harvest mechanical energy with a power density of 1.7 µW cm−2. This work is expected to motivate new design principles for fabricating piezoelectric materials with excellent mechanical and piezoelectric properties for various applications. [ABSTRACT FROM AUTHOR]

Stretchable and soft piezoresistive composites are appealing for application to tactile sensors, artificial skin, and wearable electronics. The ability of the composites to deform the geometries when they are strained can allow the electrical behavior of the composites to be manipulated. Although rigid metal and semiconductor inclusions have been utilized to create piezoresistive composites, they limit the degree of mechanical deformation. Here, liquid metal (gallium, melting point ≈ 29.7 °C) inclusion into elastomeric foam substrate with 3D open cell morphologies is utilized. Gallium is a fluidic conductor, thus it is possible to infiltrate the liquid metal into the 3D interconnected pore, resulting in soft, stretchable, and shape reconfigurable conductive composites that can change shape and function in response to external stimuli. Applying strain can enable deformation of the liquid metal, generating changes of electrical resistance. Interestingly, it is found that this piezoresistivity of the composite can be positively and negatively manipulated by adjusting the geometries of the liquid metal in the foam. Furthermore, the liquid metal in the elastomeric foam can be reversibly actuated by applying compressive force, resulting in manipulation of the restorative electrical activity of the composites. [ABSTRACT FROM AUTHOR]

Recent advances in soft, flexible, and stretchable sensors have offered a good opportunity to design various types of wearable flexible medical devices for achievement of continuous health monitoring, preventive medicine and robot feedback and control. The integration of biofunctionability with electronic skin is undoubtedly an attractive prospect in the sense that the successful medical device requires good biocompatibility, sensing capability, and high degrees of mechanical flexibility. This work summarizes the last developments in electronic skin for next‐generation medical devices that can simultaneously detect a variety of physiological information of the human body. The key properties of e‐skin that must be realized for their versatile use in medical applications are discussed in detail. Next, the paper outlines the overall applications of these sensors in wearable medicine, implantable medicine, and interventional medicine, and emphasizes how these devices monitor human health status and may be expected to replace traditional clinical tools. Finally, the challenges and future research opportunities in the field of wearable health monitoring are proposed. [ABSTRACT FROM AUTHOR]

Recent advances in materials and manufacturing processes pave the way for the establishment of piezoelectric materials via printing techniques as flexible sensors, actuators, and generators. Such flexible devices are key building blocks for future advanced robotic skin and conformable medical devices. Herein special focus is given to printed devices for its lightweight, flexibility, and manufacturing by high throughput techniques, offering a disruptive advantage in integration technologies and a wide range of opportunities for industrialization routes, where cost‐effective applications are required. In this Progress Report, the different system parameters are discussed, pinpointing the ones that affect the production of reliable flexible printed piezoelectric devices and limit this technology to achieve higher technological maturity. Focus is made on screen and inkjet printing as fabrication techniques and the well‐established piezoelectric polymer poly(vinylidene fluoride‐co‐trifluoroethylene). Key limiting factors found for the manufacturing of robust scalable all‐printed piezoelectric devices stems mainly from the piezoelectric ink production and processing. Finally, the integration of these materials, via printing technologies, into soft, flexible, and even stretchable substrates is analyzed and insights are gathered on the manufacturing trends to achieve low‐cost production of flexible piezoelectric devices embedded in electronic skin and smart wearables. [ABSTRACT FROM AUTHOR]

Graphene has great potential in wearable sensors. However, the sensing selectivity of graphene‐based sensors is still a big challenge, limiting their application in the multifunctional sensors. Herein, different types and distributions of defects are introduced into graphene by femtosecond laser patterning to realize sensing selectivity for wearable multifunctional sensors. The imperfect graphene with four pattern arrays, circle, square, triangle, and hexagon with none, right, acute, and obtuse angle, is fabricated by laser to control the types and distributions of defects. The graphene with different patterns shows remarkable sensing selectivity, owing to the dangling bonds and vacancies on the edge of patterns. The graphene‐based sensor with the circle pattern array is used to detect the strain variation; the triangle one is for temperature detection; and the hexagon one can collect the information of gas. The gauge factor is demonstrated to be as high as ≈104. The as‐produced sensor with the above‐mentioned four patterns can simultaneously detect body pulse, temperature, and harmful gas by attaching to human body or clothes, offering real‐time health monitoring and protection. The patterned graphene‐based sensors with high sensing selectivity are expected to develop multifunctional sensor platform and versatile artificial electronic skin. [ABSTRACT FROM AUTHOR]

Curved electronics, which are better coordinated and blended with the natural world due to the characteristics of large contact area, high space adaptability, etc., have been widely used in a quantity of areas ranging from conformal curved antennas and sensors in detection and measurement, to artificial smart skin of aerospace. Recent developments in curved electronics have made an increasing progress to the historic drawbacks of conventional planar electronics, however significant challenges still exist. Here, the main kinds of conformal fabrication technologies, including transfer printing, assembly techniques, curved lithography, conformal inkjet printing, 3D printing, and laser direct writing, are reviewed to realize manufacturing deformable/undeformable electronics on curved or arbitrary surfaces. The processes and features of each technology are comprehensively summarized together with their progress and potential values. Finally, the challenges and opportunities for fabricating conformal electronics on arbitrary surfaces are also discussed. [ABSTRACT FROM AUTHOR]

The emergence of ionotronic materials has substantially extended the applications of artificial skins by allowing intimate interfaces between electronics and biological/bionic surfaces toward achieving improved sensing and communication with surrounding stimuli. However, ionotronic skins are intrinsically temperature dependent, since water molecules play crucial roles in regulating both mechanical and ionic conductivity of the materials. Hence, most of the ionotronic skins will fail at temperatures below 0 °C. In this study, a highly sensitive ionotronic skin that can be used in the entire natural environmental temperature range (−30–80 °C) is developed by using silk fibroin and Ca(II) ions as starting materials. In such a system, silk fibroin serves as both structural supports and ion capture agent to provide structural stability, mechanical flexibility, and interfacial adhesion ability, while Ca(II) ions work as ionic conductor, hygroscopic agent, and deicing salt to offer highly stable ionic conductivity at a temperature range from −30 to 80 °C. These synergetic merits, together with favorable advances of silk fibroin ionotronic skins in biocompatibility, transparency, and self‐healing, allow them to be used in multiple emerging fields, such as regenerative medicine, implantable electronics, and human–machine interface. [ABSTRACT FROM AUTHOR]

Wearable optical sensors are attracting intensive research interests owing to their advantage of high sensitivity, fast response, and immunity to electromagnetic interferences. However, tunable optical properties and reconfigurable sensor structures remain great challenges for the wearable optical sensors. Herein, flexible liquid‐filled fiber adapters (FLFFAs), which are sensitive to mechanical stimuli, are demonstrated. The novel FLFFA consists of a soft liquid‐filled tubing and two silica optical fibers. The liquid core bestows the FLFFA both tunability and reconfigurability in sensing performance. Deformation of the tubing through bending or pressing results in wavelength‐insensitive changes in light transmission. By measuring the output intensity, the FLFFA based sensors achieve high angle resolution (0.18°) and low detection limit (0.7 mN) for bending and pressure sensing, respectively. The superior sensing properties together with mechanical flexibility and robustness enable real‐time monitoring of finger joint motion, respiration, and wrist pulse. Benefiting from an LED charge‐coupled device (CCD) signal recording system, a 4 × 3 keyboard is realized by simultaneously measuring the output signals of 12 FLFFAs. The FLFFA provides a promising method to detect subtle physiological signals and may find applications in healthcare devices, artificial skins, and sensor networks. [ABSTRACT FROM AUTHOR]

Soft end effectors or grippers capable of grasping objects dexterously and efficiently have attracted increasing attention in a broad range of applications. This article describes a smart soft finger‐like actuator with fast response, accurate control, self‐powered pressure, and bending sensing capability by combing the cable‐driven actuation with soft triboelectric nanogenerators (TENGs). The soft actuator, driven by a miniature DC motor, is designed to have multiple segments of elastomer body split with triangular cuts to facilitate the bending actuation and conformal contact with target objects. Two types of TENGs are integrated with the soft actuator: a single‐electrode‐mode TENG to measure the contact pressure and an inner contact–separation‐mode TENG to detect the bending. With micropyramid structures, the tribo‐skin patches possess high sensitivity and good compatibility with the actuator and can actively detect proximity, contact, and pressure via self‐generated electricity. Based on the modular design approach, a gripper with three fingers is fabricated and tested for its grasping, sensing, and self‐powering performance. This gripper is capable of picking up different kinds of objects, providing sensory feedback, and generating electricity, which shows great potential for use in robot–human and robot–environment interaction applications. [ABSTRACT FROM AUTHOR]

Melanin, a biologically occurring pigment featuring broadband optical absorption, ion‐binding affinity including antioxidative and radical‐scavenging properties, and hydration‐dependent electrical conductivity is an ideal natural semiconducting material for interfacing electronics with biological systems. Here, a skin‐mimicking optoelectronic device with a melanin nanoparticle (MNP) dispersion in a protein hydrogel–elastomer hybrid (a mimic of epidermis/dermis layers with melanin) and its application as a dopamine sensor and a UV index meter are reported. MNPs dispersed in water are placed in the elastomer reservoir with integrated silver nanowire electrodes and a transparent silk hydrogel window cover; they exhibit n‐type semiconducting behavior with increased conductivities compared with those of dehydrated MNPs. Enhanced generation of free radicals by light illumination results in an increase of the electrical conductivity. In addition, the artificial optoelectronic skin interacts with its environment through the silk hydrogel window. Applications of the device, including its use as a dopamine sensor and a UV index meter to detect dopamine and UV light passing through the window, are demonstrated. The sensitivity of the dopamine sensor is enhanced by the light illumination. [ABSTRACT FROM AUTHOR]

Here, a strain‐insensitive, durable, and visualized ultraviolet (UV) detectible multilayered artificial UV shielding skin (MUVS‐skin) is demonstrated. The electrospinning of polyurethane nanofibers and electrospraying of TiO2 nanoparticles are alternatingly conducted to assemble the MUVS‐skin. The results show that the stability of UV shielding property under different strains (50%, 100%, 150%, and 200%) is enhanced as more layers are assembled. The ultraviolet protection factor of the strain‐free MUVS‐skin (119 µm) is 10 810 and reaches to 5685 at 200% strain. Moreover, the effective transmittance (at 365 nm) of MUVS‐skin (119 µm) after being stretched for 10 000 cycles at 200% strain is only 0.125%. This stable UV shielding property is ascribed to the low‐level variation in the porosity of the multilayered structure, which originates from the enhanced slippage between adjacent layers. Furthermore, ultraviolet A (UVA) and ultraviolet B (UVB) can be precisely detected as the luminescence of blue and red for the MUVS‐skin integrates with a phosphor layer (MUVS‐skin/P). Owing to the excellent stable UV shielding property, visualized UV detection and durability against cyclic deformation, this MUVS‐skin/P might be extensively applied to the smart wearable artificial skin and protective clothing. [ABSTRACT FROM AUTHOR]

Mechanical replacement prosthetics have advanced in both esthetics and mechanical functions, but still require progress in attaining full natural functionality via tactile feedback. Through bioinspiration of the somatosensory system, recent works in the development of materials and technologies at three critical interfaces have shown great advancements: skin‐inspired multifunctionality at the prosthetic level using flexible electronics, artificial transmission of the biosignals between the prosthesis and nervous system, and stimulation and recording of these signals with mechanically compliant, implantable neural interfaces. Herein, a systematic study of the artificial skin sensation pathways for the prosthetic interfaces is discussed together with the current state‐of‐the‐art technologies and prospective strategies to enable the complete sensory feedback loop in prosthetics through the use of biomimetic sensing platforms, artificial synapses, and neural interrogation electronics. [ABSTRACT FROM AUTHOR]

Flexible and wearable magnetoelectronics add intriguing new functionalities to natural perception. Of particular interest regarding these artificial skins are wireless sensing and touchless interactions. Biocompatibility and imperceptibility are the most significant features of devices attached to the bodies. A biocompatible magnetic skin is introduced. It offers extreme flexibility, stretchability (>300%), and is lightweight, while maintaining a remanent magnetization up to 360 mT. It is comfortable to wear, can be realized in any desired shape or color, and adds tunable permanent magnetic properties to the surface it is applied to. It provides remote control functions and is combined with magnetic sensors; it implements a complete wearable magnetic system. For example, eye tracking is realized by attaching the magnetic skin to the eyelid. The advantage that it does not require any wiring makes it an extremely viable solution for soft robotics and human–machine interactions. Wearing the magnetic skin on a finger or integrated into a glove allows for remote gesture control. This type of application opens the door to new control concepts, relevant for people with disabilities, sterile environments, or the consumer industry. [ABSTRACT FROM AUTHOR]

Wearable devices have become very important for collecting health information and monitoring the condition of seriously ill patients. However, most recently developed wearable devices can only monitor limited signals within a very small range of values. A novel sensor is fabricated by modifying the surface of polyimide nanowires with silver nanoparticles. These nanowire sensors can sense both pressure and temperature changes and have antimicrobial properties. The fabricated sensor can detect a wide range of pressure variation from 5 KPa to 100 KPa. A theoretical model is developed to explain the sensing mechanism of the silver‐nanoparticle‐modified polyimide nanowires. The experimental and theoretical results for the nanowires are in good agreement. By attaching these sensors to human joints and fingers, real‐time information can be detected for human motion, such as walking or holding a hot cup of water. The excellent performance of this device shows that it has great potential for use in artificial skins for detecting temperature and human motion. [ABSTRACT FROM AUTHOR]

Electronic skin (e‐skin) integrating pressure sensors and strain sensors has shown great potential applications in smart robotics and healthcare monitoring for their flexibility and wearability. However, making the sensor low cost and highly durable for industrialization and commercialization is still a problem to be addressed. An embedded 3D printing technology is developed based on novel thermosetting printing ink which is prepared using the Ecoflex and carbon nanoparticles. The properties of the printing ink including printability and electrical conductivity are first studied and then optimized. By using this technology, a glove‐shaped e‐skin integrating both strain sensors and pressure sensors is fabricated, and the properties of the sensors are studied. Both types of sensors have excellent stability and reliability which are verified by multiple long‐term measurements (10 000 testing cycles). Specifically, the sensors possess a great shock resistance and high durability which are significant for application in real life. Furthermore, some applications for human activity monitoring and personal healthcare are demonstrated, including complex gesture recognition using 15 strain sensors, hardness sensing using pressure sensors coupled with strain sensors, and arterial pulse measurement using pressure sensors, which are promising for smart robotic sensing and wearable biomedical devices. [ABSTRACT FROM AUTHOR]

Additive manufacturing has many advantages in creating highly complex customized structures. In this study, a low‐cost multiscale stereolithography technology that can print a macroscale object with microscale surface structures with high throughput is demonstrated. The developed multiscale stereolithography is realized by dynamic switching of laser spot size and adaptively sliced layer thickness. An optical filter based on subwavelength resonance grating is used to modify laser spot size for lasers with different wavelengths and achieves a maximum resolution of 37 µm. The multiscale stereolithography process has 4.4× throughput improvement compared with the traditional stereolithography process with a single laser spot. For proof‐of‐concept testing, artificial shark skins with microriblet features are designed and 3D printed. In pipe flow experiments, the 3D printed shark skin demonstrates almost 10% average fluid drag reduction. Artificial lotus leaf surfaces are also 3D printed to demonstrate superhydrophobic property. This new process has the potential to serve as a powerful tool that can bring bioinspired structures into real‐life applications. [ABSTRACT FROM AUTHOR]

Touch sensing is the most basic but important way for organisms to interact with the outside world, and thus, fingertip skin has been widely studied to enable the manufacture of artificial skin. Sensitive multisensing integrated with perfect adhesion performance is crucial for synchronous and sensitive human physical and biochemical indicator monitoring. Here, a gecko‐inspired nanotentacle skin integrated with a microfluidic system and a polyvinylidene fluoride (PVDF)‐based piezoelectricity nanogenerator (PENG) is proposed for simultaneous multisensing. The obtained 3D nitrocellulose (NC) nanotentacle array paper is flexible and freestanding. Stainless stamps are used to imprint lithography patterns (microfluidic channels) on the NC paper, and channels with three branches are used for sweat split‐flow and sensing of pH, urea, and lactic acid. Meanwhile, the patterned substrate is integrated with a PENG, and the nanotentacles allow the substrate to conformally fit to rough skin, thus enabling sensitive sensing of micromotions (pulse beats). The results indicate that the multifunctional skin sensor is capable of sensitively monitoring the human state, thereby serving as an inspiring example for the construction of next‐generation skin with smart sensing systems. Furthermore, our sensors are amenable to a variety of applications, such as personal care, artificial skin, and human–machine interactions. A gecko‐inspired nanotentacle‐array‐based paper artificial skin for enhanced health and motion monitoring is proposed. The skin is integrated with a microfluidics system and polyvinylidene fluoride (PVDF) piezoelectricity nanogenerator for sweat index sensing and wrist pulse measurement during exercise. [ABSTRACT FROM AUTHOR]

Human skin, the largest organ of human body, can perceive tactile sensations, temperature, humidity, and other complex environmental stimulations. To mimic the capabilities of human skin, graphene provides great potential in building wearable electronic skins (E‐skins), which hold broad applications in advanced robotics, healthcare monitoring, artificial intelligence, human–machine interfaces, etc. Herein, the recent progress in flexible tactile sensors and E‐skins based on graphene material is presented. A brief introduction of the main approaches to prepare graphene nanosheets is provided. The main developments on the functions and mechanisms of bionic functional devices in E‐skins including tactile sensors, temperature sensors, and humidity sensors are then highlighted. The current and future applications for graphene‐based E‐skins, such as multifunctional biomimetic E‐skins, healthcare monitoring, and interactive human–machine interface, are also described. Finally, the existing challenges and future development trends for graphene‐based E‐skins are discussed. Graphene‐based electronic skins (E‐skins) hold great significant for building wearable and portable devices, which can precisely perceive tactile, temperature, and humidity, etc. An overview on this field is given, summarizing the recent researches and application perspectives of graphene‐based tactile sensors and E‐skins. [ABSTRACT FROM AUTHOR]