基于刺激响应材料的智能摩擦电纳米发电机: Comparison
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Please note this is a comparison between Version 3 by Sirius Huang and Version 2 by Xueqing Wang.

Smart responsive materials can respond to external stimuli through reversible mechanisms and can be directly combined with triboelectric nanogenerators (teng) to provide a variety of intelligent applications such as sensors, actuators, robotics, artificial muscles, and controlled drug delivery. Not only that, but the mechanical energy in the reversible response of innovative materials can be extracted and converted into an interpretable electrical signal.

  • smart materials
  • stimuli-responsive
  • triboelectric nanogenerator
  • energy conversion
  • self-powered system

1.Introduction

Currently, the ever-growing need for versatile and efficient intelligent devices stimulates people’s intense research interest in integrating smart response materials with traditional electronics [1,2,3][1][2][3]. The original concept of smart materials stems from natural biological systems that follow a perception-reaction-learning mechanism. Presently, they are defined as materials that can respond to a variety of external stimuli or environmental changes. This is because smart materials can adjust their function and respond accordingly by rearranging their structure at the molecular level. They represent a family of innovative materials for understanding experiences with self-awareness and purposeful responses [4,5,6,7,8][4][5][6][7][8].
Historically, applications of functional smart materials with controllable shape or volume changes in response to external stimuli have been investigated in several frontier fields, such as sensors, actuators, optoelectronic devices, information storage, and biomedicine [9,10,11,12,13][9][10][11][12][13]. These external stimuli include chemical incentives (e.g., changes in concentration, humidity, pH) [14[14][15][16],15,16], mechanical stimuli (e.g., pressure, strain) [17,18][17][18], physical stimuli (e.g., light, sound, temperature, color) [19,20,21[19][20][21][22][23],22,23], and electromagnetic stimuli (e.g., electric, magnetic, charge injection) [24,25,26,27][24][25][26][27]. The unique and excellent responsive characteristics of smart materials enable them to be used specifically and accurately in certain applications, allowing them to perceive changes in the environment and adapt future smart polymers to similar situations and specific behaviors in specific applications [28,29,30][28][29][30].
A triboelectric nanogenerator (TENG) is a newly developed energy harvesting technology based on the coupling effect of contact charge and electrostatics [31,32][31][32]. It can convert almost any type of mechanical energy, such as vibration [33], water waves [34], wind [35], raindrops [36], and human motion [37], into electrical energy, and power various sensors. In principle, TENGs have a wide selection of materials, such as organic materials [27[27][38],38], polymers [39], hydrogels [40], and elastic rubbers [41[41][42],42], which can be directly used to manufacture TENG or serve as active component of TENG systems. Thus, smart materials can also be promising candidates combined with TENG devices and generate many multifunctional applications. The introduction of smart materials not only improves the performance of TENG in terms of material optimization, but also provides various applications, such as sensors [43[43][44],44], actuators [45], robots [46], artificial muscles [47], and controlled drug delivery [48]. Moreover, the mechanical energy in the reversible response of smart materials can be cleared and converted into electrical energy, which is highly dependent on the amplitude and frequency of environmental stimuli and can be digitized for the latter. Therefore, a self-powered smart system can be constructed, with broad applications in catalysis [49], sensors [50], drug/gene delivery [51[51][52],52], and self-assembly [53,54][53][54].

2. Basic Principle and Working Modes of TENGs

TENG is capable of transforming mechanical energy from the surrounding environment into electrical power by utilizing a combination of triboelectrification and electrostatic induction effects [55,56][55][56]. Typically, this involves contacting two materials with differing charge affinities, causing electrostatic charges to build up on their surfaces until reaching saturation with repeated contact. These charges generate an electric field that drives the flow of electrons through an external load over time, ultimately converting mechanical energy into electrical energy [57,58][57][58]. TENGs can be categorized into four working modes(Figure 1): the vertical contact separation mode, which uses vertical polarization; the lateral sliding mode, utilizing lateral polarization from the relative movement between two media [59]; the single-electrode mode, which can harvest energy from a freely moving object without attaching conductive wires [60]; the independent triboelectric layer mode, which uses electrostatic induction between a pair of electrodes to generate electrical energy [61].
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Figure 1.
The basic principle of TENG.
Vertical contact separation mode is the basic model of TENG, which involves the creation of opposite charges on the surfaces of two dielectric films with distinct electron affinity upon physical contact. When there is an appropriate gap between the two films, an electric potential difference occurs between the surfaces of the two dielectric films. If the films were connected through electrodes and external circuits, the free electrons in one electrode will flow to the other to balance the electrostatic field. Once the gap is closed, the potential difference caused by the friction charge disappears, and the induced electrons flow back. Regular contact and separation between the two materials drive rated electrons to flow back and forth between the two electrodes, resulting in an AC output in the external circuit. It is the basic model of TENG. Lateral sliding mode involves relative movement in the direction parallel to the interface between two materials with opposite triboelectric polarities. When the materials are brought into contact, surface charge transfer occurs due to the triboelectrification effect. When the materials are separated by a distance, a potential difference is generated across two electrodes due to the effective dipole polarization created in parallel to the direction of the displacement. Single electrode mode converts energy by combining dielectric materials with metal electrodes. When the charged dielectric approaches the grounded metal electrode, an induction charge is created in the metal plate to balance the electrostatic field. When the dielectric moves away from the metal plate, the current flows back to the ground. SE is the most convenient and simplest mode, which harvests the energy of moving objects through only a metal plate without the need for other dielectrics. Independent triboelectric layer mode has high potential in collecting natural energy. The mode needs to place a dielectric layer on top of a pair of symmetrical electrodes that are approximately the same size as the moving object and maintain a small gap between the object and electrodes, an asymmetric charge distribution is generated via induction in the surrounding medium when the object approaches or departs from the electrodes. This occurs only if the object has been previously charged by a triboelectric process. The electrons flow between the two electrodes to balance the local potential distribution. As the object moves back and forth, the electrons oscillate between the paired electrodes and generate an AC output. This mode offers the advantage of harvesting energy from a moving object without requiring grounding, making the system more flexible. The TENG’s open circuit voltage (VOC) can easily reach several thousand volts, while the short circuit current (ISC) is as low as a few microamperes. The output voltage of a TENG decreases as the load resistance decreases. Therefore, intelligent responsive materials can be used as the friction layer or electrode layer material of TENG to improve its output characteristics. Moreover, TENG can also be used to drive some intelligent and responsive materials and devices.

3. Classifications and Underlying Mechanisms of TENGs That Are Based on Smart Materials

The self-adaptability and self-actuation of smart materials are achieved through the autonomous movement of particles at the nanoscale. When stimulated by external factors, molecules and atoms will aggregate, align, and orient themselves to provide the optimal response to the external stimuli [62,63][62][63]. If combined with TENG, the system may deliver various intelligent applications, such as sensors [64], actuators [65], robots [66], artificial muscles [67], and controlled drug delivery [68] with immediate response to stress, electrical current, temperature, magnetic field, or even chemical compounds. This section introduces the combination of different types of smart materials with TENG based on their principles and mechanisms. Table 1 lists the synthesis methods, properties, and application comparison of TENGs combined with different types of smart materials. 
Table 1.
Comparison of synthesis methods, properties and applications of TENGs combined with different types of smart materials.
Type Material Method of

Synthesis		 Performance Application References
Magnetic responsive materials γ-Fe2O3, PVDF Spin coating,

Solution casting		 0.8 µA, 90 V Scavenging energy from rotary pump vibrations. [69]
Al/Ni fabric, PDMS Solidified stripping 30 µA, 205 V Harvesting wind energy. [70]
NdFeB magnets Solution casting 1.17 mA·cm–2 Harvesting wind energy. [71]
Optical responsive materials ZnO-NPs, PVDF Solution casting 28 V Monitoring of movement. [72]
PEDOT-MeOH Sol-gel method,

Spin coating		 - Self-powered smart windows [73]
Hygro-responsive materials Chitosan-glycerol film Coating method 130 V Sweat sensor,

Monitoring of movement.		 [74]
PFSA ionomer Solution casting,

Spin coating		 - Self-powered steam sensor [75]
SnS2 Chemical vapor deposition 7.6 µA Humidity sensor [76]
Temperature-responsive material PCL, fluorinated alumina Solid–liquid mixing 85 nA, 6 V Wetting monitoring and temperature sensing [77]
CNFs, AgNWs, PA, BP Vacuum filtration 116 V, 3.8μA, 42 nC, 33.4 μm−2 Fire warning,

Temperature sensing		 [78]
NIPAM, MMA Free radical polymerization and spin-coating. 242.72 nA,

0.72 V,

10.78 nC		 A stable warning system for real-time liquid temperature monitoring [79]
pH-responsive materials PTFE, PDMS Spin coating 26.37 μA,

69.04 V		 Acid rain sensor [80]
Self-Healing materials acrylic acid,1-vinyl-3-ethyl imidazolium dicyandiamide, ZnO NPs Solution casting 3.15 W·m−2 Monitoring of movement [81]
AAM, KPS, glycerol, NH2-PDMS-NH2 Solidified stripping 157 V, 16 µA,

29 nC,

710 mW·m−2.		 Monitoring of movement [82]
PU Solution casting 180 V,

1.3 μA		 Monitoring of movement [83]
Shape-memory polymers PCL,

n-butyl acrylate		 Solidified stripping - Smart wrist splint with an alarm system. [84]
Polyurethane Electrospinning 150–320 V,

2.5–4 μA·cm−2		 Self-powered water temperature sensor. [85]
PSeDAE Cross-linking,

Laser engraving		 44.5 V, 1 μA, 17.5 nC Improvised explosive device. [86]

3.1. Magnetic Responsive Materials

In an external magnetic field, flexible materials embedded with magnetic particles can produce a series of deformations, such as stretching, deformation, and expansion. A controllable magnetic field can control these deformations of soft magnetic materials because the interaction between electrons creates a solid molecular lot in ferromagnetic materials. Ferromagnetic materials, in the process of spontaneous magnetization, will produce a small magnetization in different directions to reduce the magnetostatic energy, resulting in saturation magnetization. This is called the magnetic domain [87,88][87][88].
Thus, when a soft magnetic material is affected by the strength of an external magnetic field, the functional magnetic domains will align in the direction of the area. Magnetic soft materials are considered ideal alternative materials for specific space components due to their responsiveness, ease of handling, and self-assembly. At present, the research field and application range of intelligent magnetic response devices is less diverse than other types of response materials. In most cases, they are combined with flexible polymer materials and magnetically driven, employing unidirectional magnetization. Further investigation shows that the magnetic directions of the domains are randomly distributed due to the irregularity of the thermal motion, which causes the magnetic moments between the disciplines to cancel each other due to the opposite directions. Thus, in an external magnetic field with a strength of 0, the entire ferromagnet does not show magnetization. Once the external magnetic field drives the magnetic moment, it tends to coincide with the direction of the external magnetic field. In this dynamic process, an induced magnetic field is formed, and a magnetized current is generated. Li et al. applied magnetized wind generated by a magnetic field to ferromagnets, which improved the electrical output performance and energy conversion efficiency of TENG and opened up a breakthrough direction for studying the output characteristics of TENG [89].
The magnetic nanocomposites used to create the Magnetic Response Triboelectric Nanogenerator (TENG) offer a unique benefit beyond the additional driving force provided by the magnetizing current. Specifically, the solid magnetic response of the material enables the external magnetic field to facilitate the contact and separation of the TENG’s layers, without requiring any additional mechanical force. Therefore, it can work in non-contact mode to prevent the device from coming into direct contact with external mechanical shocks that could damage the electrodes and triboelectric layer. Bushara et al. synthesized γ-Fe2O3/PVDF transparent nanocomposites as friction layer materials for TENG by spinning coating method, thus producing TENG devices with flexibility and stretchability advantages and stability [69]. In the preparation process, PET material was used as the positive triboelectric layer material, and on one of the substrates, the spun γ-Fe2O3/PVDF was used as the negative triboelectric material. The two are connected face to face to a curved mylar film, and the spacing between them can be periodically changed by externally applied forces and create a potential difference. The TENG moves vertically in response to the attraction of the magnet. When the magnet is near the device, the magnetic nanocomposite is near the PET’s upper surface. When the magnet is removed from above the device, the PET layer and the nanocomposite layer separate due to gravity. The electrical output performance of the magnetic drive TENG in non-contact mode is 0.8 μA and 90 V, respectively. In addition, the output characteristics can be further optimized by changing the nanocomposite’s magnetized flux density or the NP embedment’s mass fraction.
In the past few years, TENG has been studied to capture wind and blue energy. Environmental factors for the outdoor energy harvesting process of the TENG in an open environment, such as gas composition, especially humidity, have a significant impact on the performance of the TENG. To adapt to wind energy and blue energy harvesting in high-modesty environments, Huang et al. proposed a magnetic-assisted non-contact TENG in which the device consists of two parts: a magnetic response layer (PDMS/FeCoNi composite/PET/Al/PDMS) and a non-magnetic response layer (Al/Ni fabric/PET) [70]. Wind or water flow can drive the rotation of the entire device, directly leading to contact separation of the magnetically assisted non-contact TENG. As the magnet rotates toward the device, the magnetic response layer is absorbed, causing the PDMS film to come into contact with the Al/Ni fabric. In contrast, the PDMS film and Al/Ni fabric separate as the magnet rotates away from the device. The blue energy can be harvested and converted into electrical energy by a contact separation between the magnetic and non-magnetic responsive layers. Obviously, the higher wind speed makes the panel spin faster, resulting in a higher frequency of contact separation between the magnetic and non-magnetic auxiliary layers.
Recently, Zhao et al. developed a magnetic elastomer generator that can change the magnetic field in a soft system through wind-induced mechanical deformation. Additionally, it can convert wind energy into electrical energy through electromagnetic induction in any direction [71]. The magnetic-elastic generator is composed of magnetic particles and a polymer matrix with Young’s modulus of 980.9 kPa, which has suitable mechanical tensile properties. The results indicate that a high current density of 1.17 mA cm−2 and an extremely low internal impedance of 68 Ω are obtained at 266 r/min and driven by ambient rain-blown wind. The system can decompose water to produce hydrogen at a rate of 7.5 × 102 mL h−1 at a wind speed of 20 m s−1. In other words, this work brings a whole new platform technology to the wind harvesting community.

3.2. Optical Responsive Materials

Light stimulation is a fundamental and straightforward approach for investigating single stimulus responses, offering fast response times, high driving performance change rates, and excellent stability [90,91,92][90][91][92]. In particular, photochromic molecules are crucial components of light-responsive materials, capable of capturing optical signals and converting them into valuable properties that can drive changes in shape and structure, as well as exhibit macroscopic characteristics [93]. Integrating photochromic materials into TENG systems enables the expansion of self-powered sensing applications and propels the development of TENG towards higher precision [94].
Santanu Jana et al. have produced a wearable polymer composite NG (PCNG), which facilitates the formation of γ crystalline phases by adding ZNO-NPs to PVDF films [72]. PCNG delivers an open-circuit voltage of up to 28 V and a short-circuit current of 450 nA by simple repetitive human finger application (at a pressure amplitude of 8.43 kPa). More importantly, when a perceptive response is generated by PCNG, where ZNO-NPs can be used as an optical probe, near-blue emission is observed from the photoluminescence spectrum.
The original model of solar-driven photo electrochromic devices (PECDs) is a hybrid system of dye-sensitized solar cells (DSSCs) and electrochromic devices (ECDs), which is a potential application for convenient self-powered applications. According to the structure design, PECDs can be divided into two classical types: separated photochromic devices (S-PECD) and combined photochromic devices (C-PECD). In order to further improve the optical contrast and reduce the response time, a novel hybrid photochromic device (H-PECD) was proposed by Cheng et al. [73]. The novel H-PECD structure comprises a photoelectrode coated with an electro-chromic conducting polymer layer, which operates independently and exhibits exceptional speed and optical variation during coloring and bleaching under diverse weather conditions. This performance is comparable to conventional ECDs while circumventing the necessity for an additional power supply or intricate wiring.

3.3. Hygro-Responsive Materials

When the external environment’s relative humidity (RH) changes, the humidity-sensitive material can produce reversible expansion and shrinkage phenomena. Meanwhile, it can convert chemical potential energy in water into mechanical energy. Therefore, changing humidity conditions can provide the driving force for the TENG to switch to the extreme environment. The moisture-sensitive TENG can effectively capture energy from wind and raindrops. On the one hand, the device can optimize the working mode and automatically switch the working structure without outside intervention, forming a wholly self-powered intelligent system. On the other hand, the particular advantages of TENGs, such as fast response speed and high output voltage, can be fully utilized. Therefore, introducing hygro-responsive materials into the TENG research route could generate some attractive diversified applications in personal health monitoring or meteorology.
Jao et al. have developed a triboelectric nanogenerator based on chitosan-glycerol thin films (C-TENG), which have resistance, environmental stability, and shape adaptability [74]. The output characteristics of the manufactured C-TENG are very stable under various humidity conditions. More importantly, the C-TENG can be combined with functional textiles to enable a self-powered sensor to detect humidity, sweat, and gait phases. With the increased NaCl concentration, the output voltage of the sweat sensor decreases from 26 V to 12.5 V. Because of this output tendency, NaCl sensors can be implemented. Since the concentration of NaCl is an essential indicator for people to monitor their physical condition during exercise, especially for high-intensity or long-term exercise, C-TENG can be used to detect the concentration in sweat.
Humidity sensing is a well-studied field of smart response. The vapor-absorbing materials used to make moisture-responsive actuators usually have porous or fibrous structures designed to allow better passage of water molecules, and the change in water molecule content will produce internal stress, thus causing spontaneous deformation. To achieve a self-actuated TENG, a steam-driven actuator is an ideal device for coupling with the TENG. Ren et al. demonstrated a wet-responsive TENG for vapor-driven materials based on perfluorinated sulfonic acid (PFSA) ionomers [75]. At relatively high (or low) concentrations of PFSA membranes, water molecules can be absorbed (or desorbed) by these nanochannels, which gradually expand (or contract) to generate internal stresses and drive TENG leaf deformation. This self-powered sensor can be used to detect vapor concentration changes and monitor vapor leakage.
In addition, materials with two-dimensional (2D) structures have significant advantages in many areas of sensors. SnS2 has the most exciting design among two-dimensional (2D) transition metal disulfide (TMD) materials, consisting of a tightly packed sheet of tin atoms sandwiched between two sheets of sulfur atoms. It is worth noting that SnS2 material has high carrier mobility compared with other TMD material structures. The essential method to obtain SnS2 with different morphologies is chemical vapor deposition (CVD). Through this method, SnS2 can acquire a large number of available active sites, which is the critical parameter to realize gas or humidity sensing. Leyla et al. made a humidity sensor based on FTO/Kapton CS-TENG using SnS2 [76]. 

3.4. Temperature-Responsive Material

An important property of temperature-responsive materials is the low critical solution temperature (LCST). LCSTS are mainly found in polymer-based materials, and the polymer will dissolve into micelles in various proportions at temperatures below the LCST. In contrast, at temperatures above the LCTS, it will form separate phases [95,96][95][96]. Intelligent temperature response TENG is vital for energy harvesting and application expansion. The current working environment of electronic devices is mostly room temperature. In fact, temperature also has a non-negligible influence on the output performance of TENG, which limits their applicability significantly. Combining the temperature-sensitive material with the TENG can not only directly and accurately judge the real-time temperature through the output signal but also serve as a probe to reflect the ambient state at different temperatures.
Li et al. utilized the intelligent temperature-regulating behavior of tribological properties to propose a poly(ε-caprolactone) (PCL)-based liquid–solid TENG. The PCL material comprises a hydrophobic backbone [-(CH2)5], hydrophilic end groups (-COOH, -OH), and amphiphilic ester groups, rendering it thermally responsive [77]. As a heterogeneous polymer, the surface of PCL will recombine when the temperature changes, even when the polymer is in a glassy state. Under relatively low temperatures (20 °C), the PCL chain migrates slowly, resembling the “frozen state”, which is the thermodynamically unstable state. As the temperature increases (40 °C), the PCL chain transitions to an “active state”, and most of the hydrophobic groups at the interface are eventually replaced by hydrophilic groups , reaching a state of thermodynamic equilibrium.
Recently, most TENGs based on biologically derived natural materials have been reported. Nanocellulose is a rich raw biomolecular material, which is renewable, bio-degradable, and highly biocompatible. Wang et al. developed a flexible and biodegradable flame retardant friction nanogenerator (FR-TENG) using cellulose nanofibrils (CNF) and phosphorous flame retardants for fire monitoring and warning purposes [78]. Tannic acid (TA) modified BPNS (TA-BPNs), and PA were added to CNF as non-toxic co-flame retardants as triboelectric layers (CNF-BP-PA films) and silver nanowires (AgNWs) as conductive layers. Compared to pure CNF films, CNF-BP-PA/AgNWs films exhibited excellent fire resistance and flame retardation, with a thermal index of 3779.16 K, indicating the film’s sensitivity to temperature. The BPNS of composite CNF-BP-PA films can be used as the flame-retardant mechanism of condensing and gas phases to achieve effective flame-retardant performance. At the initial stage of combustion, the layered structure of TA-BPNS can act as a physical barrier to prevent the transfer of pyrolytic products to the flame and simultaneously inhibit continuous combustion by generating heat. Subsequently, for the condensation phase flame retardant mechanism, BP will be oxidized to P2O5, promoting the dehydration and carbonization of the polymer, forming a protective carbon layer. In addition, P2O5 traps water molecules and includes a series of phosphoric acids that coated the surface of the material, blocking oxygen and heat from the outside world. The feasibility of FR-TENG in temperature sensing and its application in fire alarms are proven.
N-isopropyl acrylamide (NIPAM) has a thermal phase transition behavior and intelligent adjustable properties as a biologically compatible and temperature-sensitive material. Poly (n-isopropyl acrylamide) (PNIPAM) is water soluble at room temperature and has a low critical solution temperature (LCST) of 32 °C [97,98][97][98]. By changing the external temperature, it can undergo a phase transition from curl to the ball. Feng et al. prepared the temperature-sensitive NIPAM by free radical polymerization and spin coating and introduced it into L-S TENGs [79]. Due to its thermal properties, the main groups and surface wettability vary with temperature. On this basis, in order to demonstrate the practicality of the PNM-based L-S TENG, an alarm device was designed to monitor fluid pipe temperatures exceeding 30 °C. In the temperature sensor design, the tribological energy generated by water droplets flowing over the surface of PNM at different temperatures is the key to triggering the alarm. 

3.5. pH-Responsive Materials

pH-responsive materials have attracted much attention from academia and researchers in the past few decades. pH-responsive polymers are materials that respond sensitively to the pH of solution through changes in structural properties such as solubility, surface activity, configuration, and chain structure formation [99,100][99][100]. Polymer-based materials were widely used as pH response materials during their development because of their structurally weak acid/primary groups. Significant changes in pH value can lead to swelling/deswelling of polymers, dissolution/precipitation of polymer chains, or the effect of hydrophobic/hydrophilic surface characteristics on changes in surface properties.

3.6. Self-Healing Materials

During the process of mechanical energy collection, the TENG may suffer from long-term physical impact, mechanical stiffness, and chemical corrosion, which may cause equipment failure [101,102][101][102]. The sustainability and safety of the equipment are greatly affected. In conclusion, the development of self-repairing materials can effectively improve the durability of TENG and enhance the functionalization of application scenarios. Self-healing materials mimic living organisms with self-healing properties after damage and injury. Through the reconstruction of chemical bonds, self-healing materials essentially repair losses and restore the original performance of devices. Most of the self-healing polymers studied so far are in gel form. Hydrates of hydrogels or organic gels are synthesized by fixing water or organic solvents in a self-healing polymer grid. Their structure is similar to the three-dimensional structure, which makes them complement the natural organization, with excellent adaptability and flexibility.
Li et al. proposed a transparent self-healing ion gel-based TENG (SI-TENG) [81]. The self-healing gel is synthesized by in situ polymerization of acrylic acid (AA) in 1-vinyl-3-ethyl imidazolium dicyanamide ([Emim] [OAc]) with zinc acetate dihydrate and ZnO nanoparticles (NPs). SI-TENG was prepared by assembling PAA-Zn50/ZnO20/IL60 ionic gel and two 3 M 9495 tape pieces into a sandwich structure. When the cut SI-TENG was rejoined, the coordination bonds on the fractured surface gradually re-formed. The self-healing ability of PAA-Zn50/ZnO20/IL60 enables SI-TENG to maintain its original electrical output after multiple cutting/healing cycles.
The self-healing characteristic provides the TENG with excellent electrical output recovery capability, which can quickly return to its original state over a wide temperature range. The novel PAAM-Clay organic hydrogel-based TENG designed by Huang et al. can operate in a wide temperature range from −30 to 80 °C [82]. Organic hydrogels, and IU-PDMS can repair themselves and form a segment that cannot be separated by mechanical stretching. There is no significant change in mechanical properties after self-healing compared with before damage. The output properties of the new TENG are 157 V, 16μA, and 29 nC, respectively.
However, most current studies focus on preparing self-healing materials for mechanical damage, ignoring the high risk of damage caused by an electrical breakdown in TENG. Wu et al. proposed a TENG for a repairable elastomer based on a double dynamic network of hydrogen and coordination bonds [83]. After the breakdown of multiple electric fields, the mechanical self-healing efficiency of TENG is still 96%, and the electrical self-healing efficiency is almost 100%. It provides an excellent idea for TENG to avoid mechanical or electrical breakdown damage.

3.7. Shape-Memory Polymers Materials

Shape-memory polymers (SMPs) are a class of responsive materials that can change their temporary shape and recover their original shape intact in response to external stimuli. This process is due to the dissociation–association process that occurs within the dynamic interaction of the polymer [103,104][103][104]. Due to their dielectric properties, wide electron affinity range, flexibility, and barrier properties, SMPs can be used as contact materials for TENG, providing considerable benefits to the device [105]. For instance, polyurethane SMPs fabricated through photolithography have been used to prepare pyramid-patterned TENGs, which can improve the device’s lifespan [106]. This approach may represent a promising direction to enhance the durability and functional diversification of TENG devices.
Liu et al. reported an SMP-based TENG (STENG) to capture biomechanical energy and detect biomechanical motion [84]. The SMP was synthesized by incorporating a semicrystalline thermoplastic polymer in a chemically cross-linked elastomer. The shape-memory properties of semi-IPN elastomers are qualitatively demonstrated using thin films. Flat films deform into different shapes with higher temperatures. Shape recovery is triggered by changing the room temperature. By utilizing the macroscopic shape-memory ability of SMP, a wrist splint capable of shape adaptation for mechanic sensation was developed using a blend of photocurable elastomer and polycaprolactone SMP film. Additionally, this SMP film was utilized as an energy harvester for body motion. Although this is only a rough model, it has a simple manufacturing process and broad feasibility.
In addition, SMPs also can be implemented under non-thermal stimuli such as water/humidity, photoactivity, electroactivity, and magnetic activity. Xiong et al. broke through the research gap of water-activated microarchitecture shape-memory TENG with water energy harvesting and water temperature sensing capabilities. They proposed a multifunctional TENGs electro-spun microstructure pad with self-recovery capability [85]. Three scalable microfibers (MF), microspheres (MS), and microsphere-nanofiber (MSNF) pads were fabricated by electrospinning. The types of micro-structured shape-memory TENG provide triboelectric sound output (~150–320 V, ~2.5–4 μA cm−2). The shape-memory capability of the display can be adapted to a variety of temporary shapes, and the recovery rate of 100% can be achieved quickly in 10 s. The results show that electrospinning is an effective method for constructing layered microstructures without losing shape memory.
In a dynamic interaction, SMPs store only one temporal shape per shape-memory loop. Therefore, the dual shape-memory effects of heat-sensitivity, light-sensitivity, and chemical sensitivity can be achieved by using reversible dynamic bonds. Further, SMPs with triple or multiple shape-memory effects are created using noninterfering reversible interactions of two or more responses to different stimuli and combined into a system. Xuan et al. synthesized a high-permittivity poly(sebacoyl diglyceride-co-4,4′-azo dibenzoyl diglyceride) elastomer (PSeDAE) with light-to-thermal conversion and triple-shape-memory [86]. PSeDAE as a triboelectric layer constructs an Information Encoding Device (IED) based on TENG. TENG can produce tri-shape-memory effects, inducing both microscopic and macroscopic functions. The micro-scale shape-memory effect enhances the electrical memory properties of IED, enabling program editing capabilities. Meanwhile, it enables the on-demand transformation of wearable applications through macro-scale shape memory.

3.8. Multiple-Stimulus-Responsive Materials

The TENG based on stimulus-response materials is a simple and efficient device that can be accurately controlled and easily prepared. However, in real-world environments, the stimulus sources are diverse, and the application scenarios are complex and variable. Therefore, to meet the diverse requirements of such environments and to enhance the intelligent response of TENG output, a single stimulus-response material is often insufficient. To address this issue, research is currently focusing on developing updated response conditions and diversified response methods. One promising approach is the use of multi-stimulus response smart materials, which incorporate multiple functional stimulus-response groups into polymer materials. Through precise molecular structure design and effective preparation methods, these materials can achieve multiple reaction properties and explore the practicality of smart response TENG functions.
Furthermore, certain polymers exhibit sensitivity to humidity as well as other stimuli, allowing for a diverse range of design functionalities. Li et al. have demonstrated the design of two flexible actuators and grippers that can respond to dual stimuli of ethanol steam and electrostatic power. These devices are capable of completing a series of tasks such as loading, driving, transporting, and unloading objects without requiring an external power supply [65]. They can complete a series of motion tasks such as loading, driving, transportation and unloading objects without an external power supply. Xiang et al. proposed a self-powered triboelectric mechanical luminescent electronic skin (STMES) capable of detecting and discriminating between multiple stimuli [107]. An electronic skin sensor with an electro-optical dual-signal sensing mode is designed by combining the TENG and mechanical luminescence (ML). STMES operates under the synergy of TENG and ML. The electrical signal senses normal pressure or bending stress, while turning or transverse tensioning stimulates the optical signal of the mechanical luminescence spacer. Different responses in the form of electrical/optical signals distinguish mechanical stimuli.
TENG provides a straightforward and effective means to drive many electrically responsive materials and devices, leveraging its unique output characteristics. The output voltage and transmitted charge of the TENG can be precisely controlled by selecting specific operating parameters, enabling the drive and operation of these systems. To effectively navigate and control a range of TENG-based functional systems, it is crucial to maintain high output voltage levels.

References

  1. Zheng, Q.; Xu, C.; Jiang, Z.; Zhu, M.; Chen, C.; Fu, F. Smart Actuators Based on External Stimulus Response. Front. Chem. 2021, 9, 650358.
  2. Wei, J.; Li, R.; Li, L.; Wang, W.; Chen, T. Touch-Responsive Hydrogel for Biomimetic Flytrap-Like Soft Actuator. Nano-Micro Lett. 2022, 14, 182.
  3. Long, F.; Cheng, Y.; Ren, Y.; Wang, J.; Li, Z.; Sun, A.; Xu, G. Latest Advances in Development of Smart Phase Change Material for Soft Actuators. Adv. Eng. Mater. 2022, 24, 2270012.
  4. Jingcheng, L.; Reddy, V.S.; Jayathilaka, W.A.D.M.; Chinnappan, A.; Ramakrishna, S.; Ghosh, R. Intelligent Polymers, Fibers and Applications. Polymers 2021, 13, 1427.
  5. Wang, W.; Li, P.-F.; Xie, R.; Ju, X.-J.; Liu, Z.; Chu, L.-Y. Designable Micro-/Nano-Structured Smart Polymeric Materials. Adv. Mater. 2022, 34, 7877.
  6. Haq, M.A.; Su, Y.L.; Wang, D.J. Mechanical properties of PNIPAM based hydrogels: A review. Mater. Sci. Eng. C-Mater. Biol. Appl. 2017, 70, 842–855.
  7. Das, S.; Ngashangva, L.; Goswami, P. Carbon Dots: An Emerging Smart Material for Analytical Applications. Micromachines 2021, 12, 84.
  8. Hajra, S.; Sahu, M.; Sahu, R.; Padhan, A.M.; Alagarsamy, P.; Kim, H.-G.; Lee, H.; Oh, S.; Yamauchi, Y.; Kim, H.J. Significant effect of synthesis methodologies of metal-organic frameworks upon the additively manufactured dual-mode triboelectric nanogenerator towards self-powered applications. Nano Energy 2022, 98, 107253.
  9. Kim, Y.-J.; Matsunaga, Y.T. Thermo-responsive polymers and their application as smart biomaterials. J. Mater. Chem. B 2017, 5, 4307–4321.
  10. Chen, Z.; Liu, J.; Chen, Y.; Zheng, X.; Liu, H.; Li, H. Multiple-Stimuli-Responsive and Cellulose Conductive Ionic Hydrogel for Smart Wearable Devices and Thermal Actuators. Acs Appl. Mater. Interfaces 2021, 13, 1353–1366.
  11. Niu, Y.; Li, S.; Zhang, J.; Wan, W.; He, Z.; Liu, J.; Liu, K.; Ren, S.; Ge, L.; Du, X.; et al. Static-Dynamic Fluorescence Patterns Based on Photodynamic Disulfide Reactions for Versatile Information Storage. Small 2021, 17, 2102224.
  12. Zhou, Y.; Zhan, P.; Ren, M.; Zheng, G.; Dai, K.; Mi, L.; Liu, C.; Shen, C. Significant Stretchability Enhancement of a Crack-Based Strain Sensor Combined with High Sensitivity and Superior Durability for Motion Monitoring. Acs Appl. Mater. Interfaces 2019, 11, 7405–7414.
  13. Jia, F.; Huang, F.; Ouyang, S.; Cai, C.; Xu, Z.; Wu, C.; Ma, Y.; Wang, M. Design of photoactive hybrid based intelligent photodetectors for identifying the detected wavelength. J. Mater. Chem. C 2016, 4, 10797–10803.
  14. Brighenti, R.; Cosma, M.P. Swelling mechanism in smart polymers responsive to mechano-chemical stimuli. J. Mech. Phys. Solids 2020, 143, 104011.
  15. Zhao, X.; Wang, L.-Y.; Tang, C.-Y.; Zha, X.-J.; Liu, Y.; Su, B.-H.; Ke, K.; Bao, R.-Y.; Yang, M.-B.; Yang, W. Smart Ti3C2Tx MXene Fabric with Fast Humidity Response and Joule Heating for Healthcare and Medical Therapy Applications. Acs Nano 2020, 14, 8793–8805.
  16. Zhou, J.; Jiang, B.; Gao, C.; Zhu, K.; Xu, W.; Song, D. Stable, reusable, and rapid response smart pH-responsive cotton fabric based on covalently immobilized with naphthalimide-rhodamine probe. Sens. Actuators B-Chem. 2022, 355, 131310.
  17. Ozcan, M.; Cakmakci, M.; Temizer, I. Smart composites with tunable stress-strain curves. Comput. Mech. 2020, 65, 375–394.
  18. Brighenti, R.; Li, Y.; Vernerey, F.J. Smart Polymers for Advanced Applications: A Mechanical Perspective Review. Front. Mater. 2020, 7, 196.
  19. Sun, D.; Cao, R.; Wu, H.; Li, X.; Yu, H.; Guo, L. Harsh Environmental-Tolerant and High-Performance Triboelectric Nanogenerator Based on Nanofiber/Microsphere Hybrid Membranes. Materials 2023, 16, 562.
  20. Feng, Y.Q.; Lv, M.L.; Yang, M.; Ma, W.X.; Zhang, G.; Yu, Y.Z.; Wu, Y.Q.; Li, H.B.; Liu, D.Z.; Yang, Y.S. Application of New Energy Thermochromic Composite Thermosensitive Materials of Smart Windows in Recent Years. Molecules 2022, 27, 1638.
  21. Li, J.; Xu, C.; Zhang, W.Y.; Shi, P.P.; Ye, Q.; Fu, D.W. Smart and efficient opto-electronic dual response material based on two-dimensional perovskite crystal/thin film. J. Mater. Chem. C 2020, 8, 1953–1961.
  22. Li, J.N.; Lu, X.G.; Zhang, Y.; Wen, X.X.; Yao, K.K.; Cheng, F.; Wang, D.C.; Ke, X.Q.; Zeng, H.; Yang, S. Dynamic Refractive Index-Matching for Adaptive Thermoresponsive Smart Windows. Small 2022, 18, 2201322.
  23. Wang, C.; Jiang, X.; Cui, P.; Sheng, M.; Gong, X.; Zhang, L.; Fu, S. Multicolor and Multistage Response Electrochromic Color-Memory Wearable Smart Textile and Flexible Display. Acs Appl. Mater. Interfaces 2021, 13, 12313–12321.
  24. Li, J.N.; Lu, X.G.; Zhang, Y.; Cheng, F.; Li, Y.L.; Wen, X.X.; Yang, S. Transmittance Tunable Smart Window Based on Magnetically Responsive 1D Nanochains. Acs Appl. Mater. Interfaces 2020, 12, 31637–31644.
  25. Hou, Z.-L.; Ma, X.; Zhang, J.; Li, C.; Wang, Y.; Cao, M. Fascinating Electrical Transport Behavior of Topological Insulator Bi2Te3 Nanorods: Toward Electrically Responsive Smart Materials. Small 2022, 18, 2205624.
  26. Liu, X.; Li, Y.; Sun, X.; Tang, W.; Deng, G.; Liu, Y.; Song, Z.; Yu, Y.; Yu, R.; Dai, L.; et al. Off/on switchable smart electromagnetic interference shielding aerogel. Matter 2021, 4, 1735–1747.
  27. Saqib, Q.M.; Shaukat, R.A.; Chougale, M.Y.; Khan, M.U.; Kim, J.; Bae, J. Particle triboelectric nanogenerator (P-TENG). Nano Energy 2022, 100, 107475.
  28. Zhang, H.; Fan, T.J.; Chen, W.; Li, Y.C.; Wang, B. Recent advances of two-dimensional materials in smart drug delivery nano-systems. Bioact. Mater. 2020, 5, 1071–1086.
  29. Xiao, D.; Zheng, M.-T.; Wu, F.-J. A bio-inspired self-assembled asymmetrical supramolecular film for highly-sensitive fire warning, solvent response, and smart switching. Chem. Eng. J. 2023, 459, 141546.
  30. Mrinalini, M.; Prasanthkumar, S. Recent Advances on Stimuli-Responsive Smart Materials and their Applications. Chempluschem 2019, 84, 1103–1121.
  31. Fan, F.-R.; Tian, Z.-Q.; Wang, Z.L. Flexible triboelectric generator! Nano Energy 2012, 1, 328–334.
  32. Xing, F.; Jie, Y.; Cao, X.; Li, T.; Wang, N. Natural triboelectric nanogenerator based on soles for harvesting low-frequency walking energy. Nano Energy 2017, 42, 138–142.
  33. Jie, Y.; Jia, X.T.; Zou, J.D.; Chen, Y.D.; Wang, N.; Wang, Z.L.; Cao, X. Natural Leaf Made Triboelectric Nanogenerator for Harvesting Environmental Mechanical Energy. Adv. Energy Mater. 2018, 8, 1703133.
  34. Wang, N.; Zou, J.D.; Yang, Y.X.; Li, X.Y.; Guo, Y.L.; Jiang, C.; Jia, X.T.; Cao, X. Kelp-inspired biomimetic triboelectric nanogenerator boosts wave energy harvesting. Nano Energy 2019, 55, 541–547.
  35. Guo, Y.L.; Chen, Y.D.; Ma, J.M.; Zhu, H.R.; Cao, X.; Wang, N.; Wang, Z.L. Harvesting wind energy: A hybridized design of pinwheel by coupling triboelectrification and electromagnetic induction effects. Nano Energy 2019, 60, 641–648.
  36. Liu, Y.; Sun, N.; Liu, J.; Wen, Z.; Sun, X.; Lee, S.-T.; Sun, B. Integrating a Silicon Solar Cell with a Triboelectric Nanogenerator via a Mutual Electrode for Harvesting Energy from Sunlight and Raindrops. Acs Nano 2018, 12, 2893–2899.
  37. Yan, L.X.; Mi, Y.J.; Lu, Y.; Qin, Q.H.; Wang, X.Q.; Meng, J.J.; Liu, F.; Wang, N.; Cao, X. Weaved piezoresistive triboelectric nanogenerator for human motion monitoring and gesture recognition. Nano Energy 2022, 96, 107135.
  38. Khandelwal, G.; Chandrasekhar, A.; Raj, N.P.M.J.; Kim, S.-J. Metal-Organic Framework: A Novel Material for Triboelectric Nanogenerator-Based Self-Powered Sensors and Systems. Adv. Energy Mater. 2019, 9, 1803581.
  39. Lu, Y.; Mi, Y.J.; Wu, T.; Cao, X.; Wang, N. From Triboelectric Nanogenerator to Polymer-Based Biosensor: A Review. Biosensors 2022, 12, 323.
  40. Dong, L.; Wang, M.; Wu, J.; Zhu, C.; Shi, J.; Morikawa, H. Stretchable, Adhesive, Self-Healable, and Conductive Hydrogel-Based Deformable Triboelectric Nanogenerator for Energy Harvesting and Human Motion Sensing. Acs Appl. Mater. Interfaces 2022, 14, 9126–9137.
  41. Cheng, Y.; Wu, D.; Hao, S.F.; Jie, Y.; Cao, X.; Wang, N.; Wang, Z.L. Highly stretchable triboelectric tactile sensor for electronic skin. Nano Energy 2019, 64, 6600–6611.
  42. Parida, K.; Thangavel, G.; Cai, G.; Zhou, X.; Park, S.; Xiong, J.; Lee, P.S. Extremely stretchable and self-healing conductor based on thermoplastic elastomer for all-three-dimensional printed triboelectric nanogenerator. Nat. Commun. 2019, 10, 2158.
  43. Zhao, K.; Wang, Z.L.; Yang, Y. Self-Powered Wireless Smart Sensor Node Enabled by an Ultrastable, Highly Efficient, and Superhydrophobic-Surface-Based Triboelectric Nanogenerator. Acs Nano 2016, 10, 9044–9052.
  44. Md, S.; Rana, S.M.S.; Md, S.; Hye Su, S.; Selim, R.M.; Seong Hoon, J.; Jae Yeong, P. Highly Electronegative V2CTx/Silicone Nanocomposite-Based Serpentine Triboelectric Nanogenerator for Wearable Self-Powered Sensors and Sign Language Interpretation. Adv. Energy Mater. 2023, 13, 2203812.
  45. Chen, X.; Pu, X.; Jiang, T.; Yu, A.; Xu, L.; Wang, Z.L. Tunable Optical Modulator by Coupling a Triboelectric Nanogenerator and a Dielectric Elastomer. Adv. Funct. Mater. 2017, 27, 1603788.
  46. Liu, S.; Li, Y.; Guo, W.; Huang, X.; Xu, L.; Lai, Y.-C.; Zhang, C.; Wu, H. Triboelectric nanogenerators enabled sensing and actuation for robotics. Nano Energy 2019, 65, 104005.
  47. Li, Y.; Chen, W.; Lu, L. Wearable and Biodegradable Sensors for Human Health Monitoring. ACS Appl. Bio Mater. 2021, 4, 122–139.
  48. Adhikary, P.; Mahmud, M.A.P.; Solaiman, T.; Lin, Z. Recentadvances on biomechanical motion-driven triboelectric nanogenerators for drug delivery. Nano Today 2022, 45, 101513.
  49. Dong, F.; Pang, Z.; Lin, Q.; Wang, D.; Ma, X.; Song, S.; Nie, S. Triboelectric nanogenerator enhanced radical generation in a photoelectric catalysis system via pulsed direct-current. Nano Energy 2022, 100, 107515.
  50. Wang, S.; Yuan, F.; Liu, S.; Zhou, J.; Xuan, S.; Wang, Y.; Gong, X. A smart triboelectric nanogenerator with tunable rheological and electrical performance for self-powered multi-sensors. J. Mater. Chem. C 2020, 8, 3715–3723.
  51. Mi, Y.J.; Lu, Y.; Shi, Y.L.; Zhao, Z.Q.; Wang, X.Q.; Meng, J.J.; Cao, X.; Wang, N. Biodegradable Polymers in Triboelectric Nanogenerators. Polymers 2023, 15, 222.
  52. Nardekar, S.S.; Krishnamoorthy, K.; Manoharan, S.; Pazhamalai, P.; Kim, S.-J. Two Faces Under a Hood: Unravelling the Energy Harnessing and Storage Properties of 1T-MoS2 Quantum Sheets for Next-Generation Stand-Alone Energy Systems. ACS Nano 2022, 16, 3723–3734.
  53. Meng, Q.; Zhang, M.; Tang, R.; Jin, W.; Zhang, J.; Lan, Z.; Shi, S.; Shen, X.; Sun, Q. Stretchable triboelectric nanogenerator with exteroception-visualized multifunctionality. J. Mater. Chem. A 2022, 10, 4300–4305.
  54. Dong, K.; Peng, X.; Wang, Z.L. Fiber/Fabric-Based Piezoelectric and Triboelectric Nanogenerators for Flexible/Stretchable and Wearable Electronics and Artificial Intelligence. Adv. Mater. 2019, 32, 1902549.
  55. Pang, L.; Li, Z.; Zhao, Y.; Zhang, X.; Du, W.; Chen, L.; Yu, A.; Zhai, J. Triboelectric Nanogenerator Based on Polyimide/Boron Nitride Nanosheets/Polyimide Nanocomposite Film with Enhanced Electrical Performance. Acs Appl. Electron. Mater. 2022, 4, 3027–3035.
  56. Ma, M.; Kang, Z.; Liao, Q.; Zhang, Q.; Gao, F.; Zhao, X.; Zhang, Z.; Zhang, Y. Development, applications, and future directions of triboelectric nanogenerators. Nano Res. 2018, 11, 2951–2969.
  57. Wen, J.; He, H.; Niu, C.; Rong, M.; Huang, Y.; Wu, Y. An improved equivalent capacitance model of the triboelectric nanogenerator incorporating its surface roughness. Nano Energy 2022, 96, 107070.
  58. Dharmasena, R.D.I.G.; Jayawardena, K.D.G.I.; Mills, C.A.; Dorey, R.A.; Silva, S.R.P. A unified theoretical model for Triboelectric Nanogenerators. Nano Energy 2018, 48, 391–400.
  59. Lee, Y.; Kang, S.G.; Jeong, J. Sliding triboelectric nanogenerator with staggered electrodes. Nano Energy 2021, 86, 106062.
  60. Wu, Y.H.; Luo, Y.; Qu, J.K.; Daoud, W.A.; Qi, T. Sustainable and shape-adaptable liquid single-electrode triboelectric nanogenerator for biomechanical energy harvesting. Nano Energy 2020, 75, 105027.
  61. Wang, Y.Q.; Yu, X.; Yin, M.F.; Wang, J.L.; Gao, Q.; Yu, Y.; Cheng, T.H.; Wang, Z.L. Gravity triboelectric nanogenerator for the steady harvesting of natural wind energy. Nano Energy 2021, 82, 105740.
  62. You, Y.; Peng, W.L.; Xie, P.; Rong, M.Z.; Zhang, M.Q.; Liu, D. Topological rearrangement-derived homogeneous polymer networks capable of reversibly interlocking: From phantom to reality and beyond. Mater. Today 2020, 33, 45–55.
  63. Edwards, C.E.R.; Mai, D.J.; Tang, S.C.; Olsen, B.D. Molecular anisotropy and rearrangement as mechanisms of toughness and extensibility in entangled physical gels. Phys. Rev. Mater. 2020, 4, 015602.
  64. Chen, C.; Chen, L.; Wu, Z.; Guo, H.; Yu, W.; Du, Z.; Wang, Z.L. 3D double-faced interlock fabric triboelectric nanogenerator for bio-motion energy harvesting and as self-powered stretching and 3D tactile sensors. Mater. Today 2020, 32, 84–93.
  65. Zheng, L.; Dong, S.; Nie, J.; Li, S.; Ren, Z.; Ma, X.; Chen, X.; Li, H.; Wang, Z.L. Dual-Stimulus Smart Actuator and Robot Hand Based on a Vapor-Responsive PDMS Film and Triboelectric Nanogenerator. Acs Appl. Mater. Interfaces 2019, 11, 42504–42511.
  66. Ji, S.; Shin, J.; Yoon, J.; Lim, K.-H.; Sim, G.-D.; Lee, Y.-S.; Kim, D.H.; Cho, H.; Park, J. Three-dimensional skin-type triboelectric nanogenerator for detection of two-axis robotic-arm collision. Nano Energy 2022, 97, 107225.
  67. Yang, D.; Kong, X.; Ni, Y.; Ren, Z.; Li, S.; Nie, J.; Chen, X.; Zhang, L. Ionic polymer-metal composites actuator driven by the pulse current signal of triboelectric nanogenerator. Nano Energy 2019, 66, 104139.
  68. Du, S.; Zhou, N.; Xie, G.; Chen, Y.; Suo, H.; Xu, J.; Tao, J.; Zhang, L.; Zhu, J. Surface-engineered triboelectric nanogenerator patches with drug loading and electrical stimulation capabilities: Toward promoting infected wounds healing. Nano Energy 2021, 85, 106004.
  69. Fatma, B.; Bhunia, R.; Gupta, S.; Verma, A.; Verma, V.; Garg, A. Maghemite/Polyvinylidene Fluoride Nanocomposite for Transparent, Flexible Triboelectric Nanogenerator and Noncontact Magneto-Triboelectric Nanogenerator. Acs Sustain. Chem. Eng. 2019, 7, 14856–14866.
  70. Huang, L.-b.; Xu, W.; Bai, G.; Wong, M.-C.; Yang, Z.; Hao, J. Wind energy and blue energy harvesting based on magnetic-assisted noncontact triboelectric nanogenerator. Nano Energy 2016, 30, 36–42.
  71. Zhao, X.; Nashalian, A.; Ock, I.W.; Popoli, S.; Xu, J.; Yin, J.; Tat, T.; Libanori, A.; Chen, G.; Zhou, Y.; et al. A Soft Magnetoelastic Generator for Wind-Energy Harvesting. Adv. Mater. 2022, 34, 2204238.
  72. Jana, S.; Garain, S.; Ghosh, S.K.; Sen, S.; Mandal, D. The preparation ofγ-crystalline non-electrically poled photoluminescant ZnO–PVDF nanocomposite film for wearable nanogenerators. Nanotechnology 2016, 27, 445403.
  73. Cheng, C.-Y.; Chiang, Y.-J.; Yu, H.-F.; Hsiao, L.-Y.; Yeh, C.-L.; Chang, L.-Y.; Ho, K.-C.; Yeh, M.-H. Designing a hybrid type photoelectrochromic device with dual coloring modes for realizing ultrafast response/high optical contrast self-powered smart windows. Nano Energy 2021, 90, 106575.
  74. Jao, Y.-T.; Yang, P.-K.; Chiu, C.-M.; Lin, Y.-J.; Chen, S.-W.; Choi, D.; Lin, Z.-H. A textile-based triboelectric nanogenerator with humidity-resistant output characteristic and its applications in self-powered healthcare sensors. Nano Energy 2018, 50, 513–520.
  75. Ren, Z.; Ding, Y.; Nie, J.; Wang, F.; Xu, L.; Lin, S.; Chen, X.; Wang, Z.L. Environmental Energy Harvesting Adapting to Different Weather Conditions and Self-Powered Vapor Sensor Based on Humidity-Responsive Triboelectric Nanogenerators. ACS Appl. Mater. Interfaces 2019, 11, 6143–6153.
  76. Leyla, S.; Nassim, R.; Maryam, B.; Somayeh, F.; Azam, I.; Raheleh, M. Self-Powered Humidity Sensors Based on SnS2 Nanosheets. ACS Appl. Nano Mater. 2022, 5, 17123–17132.
  77. Li, X.; Zhang, L.; Feng, Y.; Zheng, Y.; Wu, Z.; Zhang, X.; Wang, N.; Wang, D.; Zhou, F. Reversible Temperature-Sensitive Liquid–Solid Triboelectrification with Polycaprolactone Material for Wetting Monitoring and Temperature Sensing. Adv. Funct. Mater. 2021, 21, 2010220.
  78. Wang, R.; Ma, J.; Ma, S.; Zhang, Q.; Li, N.; Ji, M.; Jiao, T.; Cao, X. A biodegradable cellulose-based flame-retardant triboelectric nanogenerator for fire warning. Chem. Eng. J. 2022, 450, 137985.
  79. Feng, M.; Kong, X.; Feng, Y.; Li, X.; Luo, N.; Zhang, L.; Du, C.; Wang, D. A New Reversible Thermosensitive Liquid–Solid TENG Based on a P(NIPAM-MMA) Copolymer for Triboelectricity Regulation and Temperature Monitoring. Small 2022, 8, 2201442.
  80. Liu, H.; Dong, J.; Zhou, H.; Yang, X.; Xu, C.; Yao, Y.; Zhou, G.; Zhang, S.; Song, Q. Real-Time Acid Rain Sensor Based on a Triboelectric Nanogenerator Made of a PTFE–PDMS Composite Film. ACS Appl. Electron. Mater. 2021, 3, 4162–4171.
  81. Li, H.; Xu, F.; Guan, T.; Li, Y.; Sun, J. Mechanically and environmentally stable triboelectric nanogenerator based on high-strength and anti-compression self-healing ionogel. Nano Energy 2021, 90, 106645.
  82. Huang, L.-B.; Dai, X.; Sun, Z.; Wong, M.-C.; Pang, S.-Y.; Han, J.; Zheng, Q.; Zhao, C.-H.; Kong, J.; Hao, J. Environment-resisted flexible high performance triboelectric nanogenerators based on ultrafast self-healing non-drying conductive organohydrogel. Nano Energy 2021, 82, 105724.
  83. Wu, Z.; Chen, J.; Boukhvalov, D.W.; Luo, Z.; Zhu, L.; Shi, Y. A new triboelectric nanogenerator with excellent electric breakdown self-healing performance. Nano Energy 2021, 85, 105990.
  84. Liu, R.; Kuang, X.; Deng, J.; Wang, Y.-C.; Wang, A.C.; Ding, W.; Lai, Y.-C.; Chen, J.; Wang, P.; Lin, Z.; et al. Shape Memory Polymers for Body Motion Energy Harvesting and Self-Powered Mechanosensing. Adv. Mater. 2018, 30, 1705195.
  85. Xiong, J.; Luo, H.; Gao, D.; Zhou, X.; Cui, P.; Thangavel, G.; Parida, K.; Lee, P.S. Self-restoring, waterproof, tunable microstructural shape memory triboelectric nanogenerator for self-powered water temperature sensor. Nano Energy 2019, 61, 584–593.
  86. Xuan, H.; Guan, Q.; Tan, H.; Zuo, H.; Sun, L.; Guo, Y.; Zhang, L.; Neisiany, R.E.; You, Z. Light-Controlled Triple-Shape-Memory, High-Permittivity Dynamic Elastomer for Wearable Multifunctional Information Encoding Devices. ACS Nano 2022.16.1 6954–16965.
  87. Van Vleck, J.H. A Survey of the Theory of Ferromagnetism. Rev. Mod. Phys. 1945, 17, 27–47.
  88. Kittel, C. Theory of the Structure of Ferromagnetic Domains in Films and Small Particles. Phys. Rev. 1946, 70, 965–971.
  89. Li, Y.; Li, G.; Zhang, P.; Zhang, H.; Ren, C.; Shi, X.; Cai, H.; Zhang, Y.; Wang, Y.; Guo, Z.; et al. Contribution of Ferromagnetic Medium to the Output of Triboelectric Nanogenerators Derived from Maxwell’s Equations. Adv. Energy Mater. 2021, 11, 2003921.
  90. Hariharan, P.S.; Pan, C.J.; Karthikeyan, S.; Xie, D.X.; Shinohara, A.; Yang, C.L.; Wang, L.; Anthony, S.P. Solvent vapour induced rare single-crystal-to-single-crystal transformation of stimuli-responsive fluorophore: Solid state fluorescence tuning, switching and role of molecular conformation and substituents. Dye. Pigment. 2020, 174, 108067.
  91. Hu, S.Q.; Jiang, H.P.; Zhu, J.Q.; Wang, J.Q.; Wang, S.H.; Tang, J.B.; Zhou, Z.X.; Liu, S.J.; Shen, Y.Q. Tumor-specific fluorescence activation of rhodamine isothiocyanate derivatives. J. Control. Release 2021, 330, 842–850.
  92. Kazem-Rostami, M.; Akhmedov, N.G.; Faramarzi, S. Molecular lambda shape light-driven dual switches: Spectroscopic and computational studies of the photoisomerization of bisazo Troger base analogs. J. Mol. Struct. 2019, 1178, 538–543.
  93. Luo, Y.Y.; Zhang, Z.X.; Su, C.Y.; Zhang, W.Y.; Shi, P.P.; Ye, Q.; Fu, D.W. Tunable optoelectronic response multifunctional materials: Exploring switching and photoluminescence integrated in flexible thin films/crystals. J. Mater. Chem. C 2020, 8, 7089–7095.
  94. Liu, Y.Q.; Li, E.L.; Yan, Y.J.; Lin, Z.N.; Chen, Q.Z.; Wang, X.M.; Shan, L.T.; Chen, H.P.; Guo, T.L. A one-structure-layer PDMS/Mxenes based stretchable triboelectric nanogenerator for simultaneously harvesting mechanical and light energy. Nano Energy 2021, 86, 106118.
  95. Bi, S.C.; Feng, C.; Wang, M.Y.; Kong, M.; Liu, Y.; Cheng, X.J.; Wang, X.P.; Chen, X.G. Temperature responsive self-assembled hydroxybutyl chitosan nanohydrogel based on homogeneous reaction for smart window. Carbohydr. Polym. 2020, 229, 115557.
  96. Jochum, F.D.; Theato, P. Temperature- and light-responsive smart polymer materials †. Chem. Soc. Rev. 2012, 42, 7468–7483.
  97. Dhamecha, D.; Le, D.; Chakravarty, T.; Perera, K.; Dutta, A.; Menon, J.U. Fabrication of PNIPAm-based thermoresponsive hydrogel microwell arrays for tumor spheroid formation. Mater. Sci. Eng. C-Mater. Biol. Appl. 2021, 125, 112100.
  98. Li, C.; Li, M.; Ni, Z.S.; Guan, Q.W.; Blackman, B.R.K.; Saiz, E. Stimuli-responsive surfaces for switchable wettability and adhesion. J. R. Soc. Interface 2021, 18, 20210162.
  99. Sun, J.; Wang, Z.; Cao, A.; Sheng, R. Synthesis of crosslinkable diblock terpolymers PDPA-b-P(NMS-co-OEG) and preparation of shell-crosslinked pH/redox-dual responsive micelles as smart nanomaterials †. RSC Adv. 2019, 9, 34535–34546.
  100. Kocak, G.; Tuncer, C.; Bütün, V. pH-Responsive polymers. Polym. Chem. 2016, 8, 144–176.
  101. Li, C.; Guo, H.; Wu, Z.; Wang, P.; Zhang, D.; Sun, Y. Self-Healable Triboelectric Nanogenerators: Marriage between Self-Healing Polymer Chemistry and Triboelectric Devices. Adv. Funct. Mater. 2023, 33, 2208372.
  102. Liu, P.; Sun, N.; Mi, Y.; Luo, X.; Dong, X.; Cai, J.; Jia, X.; Ramos, M.A.; Hu, T.S.; Xu, Q. Ultra-low CNTs filled high-performance fast self-healing triboelectric nanogenerators for wearable electronics. Compos. Sci. Technol. 2021, 208, 108733.
  103. Korde, J.M.; Kandasubramanian, B. Naturally biomimicked smart shape memory hydrogels for biomedical functions. Chem. Eng. J. 2020, 379, 122430.
  104. Delaey, J.; Dubruel, P.; Van Vlierberghe, S. Shape-Memory Polymers for Biomedical Applications. Adv. Funct. Mater. 2020, 30, 1909047.
  105. Xu, W.; Wong, M.C.; Guo, Q.Y.; Jia, T.Z.; Hao, J.H. Healable and shape-memory dual functional polymers for reliable and multipurpose mechanical energy harvesting devices. J. Mater. Chem. A 2019, 7, 16267–16276.
  106. Lee, J.H.; Hinchet, R.; Kim, S.K.; Kim, S.; Kim, S.W. Shape memory polymer-based self-healing triboelectric nanogenerator. Energy Environ. Sci. 2015, 8, 3605–3613.
  107. Xiang, Z.; Zekun, L.; Wenwen, D.; Yilin, Z.; Wei, W.; Linlin, P.; Li, C.; Aifang, Y.; Junyi, Z. Self-powered triboelectric-mechanoluminescent electronic skin for detecting and differentiating multiple mechanical stimuli. Nano Energy 2022, 96, 107115.
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