1-Vinyl-3-butylimidazolium bromide (VBImBr, 99%) was purchased from the Lanzhou Institute of Chemical Physics (China). 1-vinylimidazole (≥ 99%), 2,6-ditert-butyl-4-methylphenol (BHT, 99%), and 1,3,5-tris(bromomethyl)benzene (98%) were purchased from Sigma-Aldrich. PVA was purchased from Sinopharm Chemical Reagent Co., Ltd. (China), with an average degree of polymerization (DP) of 1750 ± 50. Activated carbon (YP-50F) and carbon black were purchased from Kuraray Co., Ltd and 9 Ding Chemistry Co., Ltd, respectively. Ecoflex 00-50 silicone rubber was purchased from Smooth-On Company, USA. All other chemicals (analytical grade) were purchased from Sinopharm Chemical Reagent Co., Ltd. (China), and used without further purification.

Ti₃C₂T_x MXene (MXene) was synthesized according to the following process. First, 1 g LiF was added to 40 mL HCl solution (9 mol L⁻¹) and stirred for 30 min. Secondly, 1 g Ti₃AlC₂ powder was slowly added to the above solution and stirred at 35 °C for 48 h. Finally, the reaction solution was washed by centrifugation with water until the pH of the solution was ≥ 6, and the precipitate was collected. Subsequently, the precipitate was sonicated with ethanol and water, and was centrifuged at 3500 r min⁻¹ for 25 min; the upper dark green liquid was the delaminated MXene nanosheet aqueous solution.

1,3,5-tris (1′-methylene-3′-vinylimidazolium bromide) benzene (termed Ph-3MVIm-Br; Ph = phenyl, 3 denotes the number of branched polymerizable ion pairs, MVIm = 1-methylene-3-vinylimidazolium cation, Br = bromide anion) was synthesized according to Ref. [28]; the detailed synthesis process was shown in the supporting information.

Firstly, 1 g PVA power was added to 9 g deionized water under stirring at 90 °C for 4 h until PVA was completely dissolved to form 10 wt% PVA solution. Then, VBImBr (1.848 g, 8 mol L⁻¹), Ph-3MVIm-Br (12.77 mg, 0.02 mol L⁻¹), MXene (27.72 mg, 1.5 wt%, relative to monomer), and 10% PVA aqueous solution (1 mL) were added into an irradiation flask and ultrasonic dispersed. Subsequently, the solution was bubbled by N₂ for 10 min. The above solution was placed at − 25 °C for 12 h and then thawing 6 h to forming physical cross-linked gel. Finally, the above physical cross-linked gel was irradiated under an electron-beam (EB) accelerator (10 MeV, EL PONT Co., Ltd. China) with the dose rate of 10 kGy pass⁻¹ to obtain PMP DN ICH.

The chemical structure of the Ph-3MVIm-Br was analyzed by ¹H nuclear magnetic resonance (¹H NMR) using D₂O as the solvent. Fourier-transform infrared (FTIR, Tensor 27, Bruker) spectrometry and scanning electron microscope (SEM, SU8000, Hitachi, Japan) were used to confirm the structure and composition of the freeze-dried PMP DN ICH. The thermal stability of the PMP DN ICH was carried on a thermogravimetric analysis (TGA) (Q600 SDT) under N₂ gas atmosphere with a heating rate of 10 °C min⁻¹. Differential scanning calorimetry (DSC) was performed using a TA Q200 instrument. X-ray diffraction (XRD) was tested by Rigaku corporation (Japan) diffractometer. Cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), galvanostatic charge/discharge (GCD) were measured by an electrochemical workstation (CHI660E, Chenhua, Shanghai). The cycling stability was tested with a LANBTS electrochemical instrument. The open-circuit voltage, short-circuit current, and transferred charge amount were recorded by a Keithley 6514 electrometer.

The ionic conductivity of the PMP DN ICH was measured on the electrochemical workstation. The PMP DN ICH (diameter of 13 mm, thickness of approximately 8 mm) was sandwiched between two sheet metal electrodes. Next the electrochemical impedance spectroscopy (EIS) was measured at different temperatures (− 60, − 25, 0, 25, 40, 60, and 80 °C). It was calculated by Eq. (1):

where l (mm) represents the thickness of the PMP DN ICH, R (Ω) represents the bulk resistance, and S (mm²) represents the contact area of the PMP DN ICH. The samples were tested in parallel in three groups.

The adhesive strength and mechanical properties of the PMP DN ICH were measured by using the tensile testing machine (CMT-4104, Shenzhen sans testing machine Co., Ltd.). The adhesive strength testing method of the PMP DN ICH is shown in Fig. S12c. Cut the PMP DN ICH into regular-shaped samples (30 mm × 20 mm × 3 mm), and sandwich them between two substrates. Next, the tensile testing machine with a 100 N load cell broken the PMP DN ICH at a rate of 50 mm min⁻¹. The experimental results of the adhesive strength were based on the results of at least 3 samples. Besides, the cyclic tensile tests of the PMP DN ICH (40 mm × 10 mm × 3 mm) were also carried out on the tensile testing machine under the rate of 200 mm min⁻¹.

The sensing properties of the PMP DN ICH-based strain sensor were evaluated by the relative changes of the resistance. By loading the PMP DN ICH onto the tensile testing machine and connecting it to the electrochemical workstation with copper wires, the strain-induced resistance change of the PMP DN ICH can be monitored in real time. The relative rate of change of the resistance was calculated by Eq. (2):

where R and R₀ are the resistance without and with stretching, respectively.

The PMP DN ICH was cut into a cuboid shape (40 mm × 10 mm × 3 mm) and adhered to the various joints of the human body (finger, wrist, neck, belly, and knee) to detect the human motion. Then, the two ends of the PMP DN ICH were connected to an electrochemical workstation or a small portable wireless transmission device. This experiment was completed with the assistance of a volunteer, and informed written consent was obtained for publishing the images and data. The gel was not harmful to humans.

The resistance of the sensor at various temperatures was measured by the electrochemical workstation. The temperature coefficient of resistance (TCR) was calculated via Eq. 3:

where R₀ (Ω): the initial resistance of the PMP DN ICH at 25 °C; ΔR (Ω): the relative change of resistance; and ΔT (°C): the relative change of temperature.

An appropriate amount of NMP solution was added dropwise to the mixture of activated carbon, carbon black, and PVDF powder with a mass ratio of 85:5:10. After fully grinding and uniform, the mixed slurry was applied to the cleaned rectangle nickel foam (1 × 2 cm²) and dried in vacuum at 50 °C for 48 h. The total mass load of electrode material was about 3.0 mg. Then, the activated carbon electrode was performed by a powder tablet press (YP-40 T, Tianjin Jinfulun technology Co., Ltd) under a pressure of 10 MPa. The SCs was assembled by the activated carbon electrodes and the PMP DN ICH with a sandwich structure. Finally, two titanium foils as current collector and conductive wire were placed on both sides of the sample and sealed with PDMS. Electrochemical performance was tested after standing 1 h.

The PMP DN ICH-TENG was fabricated by sandwiching the PMP DN ICH with commercial kapton film and ecoflex, where PMP DN ICH, kapton film, and ecoflex classed as the electrode, the negative and positive electrification layer, respectively. And the Ag wire was attached to PMP DN ICH for electrical output measurements.

MXene nanosheets were synthesized according to our previously reported method [29]. The IL 1,3,5-tris(1′-methylene-3′-vinylimidazolium bromide) benzene (Ph-3MVIm-Br) was used as a cross-linker after being synthesized by alkylation. The chemical structure of Ph-3MVIm-Br was determined by ¹H nuclear magnetic resonance spectroscopy (Fig. S1). PMP DN ICH was prepared using a two-step method (Fig. 1a) that involved dissolving the IL monomer 1-vinyl-3-butylimidazolium bromide (VBImBr) and IL cross-linker Ph-3MVIm-Br in a 10% aqueous PVA solution, and then ultrasonically dispersing a certain amount of the MXene into the preceding solution. A physically cross-linked network was readily obtained from the resulting black precursor solution by freeze-thawing. Subsequently, a chemically cross-linked PIL-PVA network was constructed by the in situ polymerization/cross-linking driven by the ionizing radiation technique. Finally, black-colored PMP DN ICH with abundant covalent and noncovalent cross-linked networks was successfully obtained (Fig. 1b). The radiation-associated conditions for synthesizing PMP DN ICH were comprehensively optimized (Figs. S2 and S3) and determined to be as follows: absorbed dose, 20 kGy; monomer concentration, 8 mol L⁻¹; cross-linker concentration, 0.02 mol L⁻¹; and MXene content, 1.5 wt%. The gel synthesized under these conditions was used in the subsequent experiments.

Fourier-transform infrared (FTIR) spectra of VBImBr, Ph-3MVIm-Br, the MXene, PVA, and PMP DN ICH were acquired (Fig. 1c). The imidazolium-associated peaks at 1157 and ~ 3000 cm⁻¹ appeared in the spectrum of PMP DN ICH after the irradiation step, indicating that the imidazole ring structure was not damaged by irradiation. Moreover, the characteristic -C=C- peaks at 924-981 and 1648 cm⁻¹ almost disappeared after the irradiation, indicating successful polymerization/cross-linking of PMP DN ICH [30]. Additionally, peaks appeared at 3296 and 1086 cm⁻¹, presumably owing to the stretching vibrations of -OH groups in the PVA chains [31]; these peaks shifted to 3367 and 1093 cm⁻¹, respectively, in the spectrum of PMP DN ICH, suggesting hydrogen bond formation [32]. X-ray diffractometry (XRD) analysis of PVA, the MXene, and PMP DN ICH (Fig. 1d) indicated that the typical PVA crystalline peaks corresponding to the (101), (200), and (102) lattice planes almost completely receded in the pattern of PMP DN ICH, suggesting that the PVA in PMP DN ICH could be chemically cross-linked [33]. Additionally, the intensity of the (002) peak of the MXene in PMP DN ICH decreased and shifted to a lower 2θ value, implying that the d-spacing of the MXene could have increased slightly, possibly owing to hydrogen bonding between the MXene and the other components [34,35]. Scanning electron microscopy (SEM) revealed the highly porous nature of PMP DN ICH (Fig. 1e), and energy-dispersive X-ray spectroscopy (EDS) mapping confirmed the uniform distribution of Ti in PMP DN ICH, suggesting a regular distribution of the MXene (Fig. S4). Overall, these findings validated the synthesis of PMP DN ICH with a homogeneously cross-linked network featuring abundant covalent and noncovalent interactions using the aforementioned meticulous design approach.

The mechanical performance, environmental tolerance, and conductivity of PMP DN ICH were explored to determine its applicability in flexible electronic devices. Moreover, when the PMP DN ICH was attached on the skin surface as a wearable material to detect human movement, adhesion was also key influencing factors. As shown in Fig. S5, PMP DN ICH exhibited enhanced mechanical performance owing to its chemically cross-linked structure that was generated by ionizing radiation. Moreover, it showed remarkable mechanical elasticity and shape recovery, given its ability to undergo large stretching and compression without any evident structural deformation and then quickly return to its initial shape after stress removal (Fig. 2a, b). PMP DN ICH was subjected to 10 successive tensile-relaxation cycles (ε = 100%) and compression-relaxation cycles (ε = 70%) to quantitatively examine its fatigue resistance and cycling stability (Fig. 2c, d). After displaying hysteresis in the first loading-unloading cycle, the stress-strain curves of PMP DN ICH in the subsequent cycles almost overlapped, indicating decent elastic behavior and fatigue resistance [36,37]. In contrast, the hydrogel precursor Pre-PMP DN ICH exhibited inferior fatigue resistance and cycling stability (Fig. S6a-d).

To achieve practical viability, ICHs must exhibit acceptable performance under extreme conditions in terms of aspects such as temperature resistance, long-term stability, and anti-drying properties. To that end, the temperature resistance of Pre-PMP DN ICH and PMP DN ICH was analyzed under extreme storage conditions (Figs. 2e and S6e). The results indicated that both materials exhibited outstanding flexibility in terms of being effortlessly twisted/compressed and being bent at − 60 °C. However, Pre-PMP DN ICH which had a physically cross-linked structure could not be used at high temperatures because its structure was destroyed after only 10 min at 80 °C (Fig. S7). Temperature-dependent tensile and compressive stress-strain curves of Pre-PMP DN ICH (Fig. S6f, g) and PMP DN ICH (Fig. 2f, g) suggested that the mechanical strength increased and the ductility decreased with decreasing temperature. Notably, PMP DN ICH exhibited satisfactory tensile stress-strain and compressive stress-strain characteristics at − 60 °C (98.6 kPa-195% and 559.4 kPa-78.3%, respectively) in terms of meeting practical application requirements. This level of mechanical flexibility of PMP DN ICH at extreme temperatures can be leveraged to significantly broaden its applicability.

The conductivities of Pre-PMP and PMP DN ICH at different temperatures were investigated by electrochemical impedance spectroscopy (EIS) (Figs. 2h and S8). The conductivity of Pre-PMP DN ICH increased from 70.26 mS cm⁻¹ at − 60 °C to 141.08 mS cm⁻¹ at 60 °C, whereas that of PMP DN ICH increased from 37.65 mS cm⁻¹ at − 60 °C to 139.21 mS cm⁻¹ at 80 °C. The results indicate the stable ion-transporting tendency of the DN ICH at extreme temperatures. The excellent conductivity of PMP DN ICH in harsh environments was corroborated by comparison with those of previously reported temperature-tolerant hydrogels (Fig. S9). Additionally, PMP DN ICH was used as a wire in a circuit to illuminate a light-emitting diode (LED) using a 3 V power source (Fig. S10 and Movies S1, S2). Stretching or compressing PMP DN ICH led to commensurate changes in the brightness of the LED lamp.

The long-term stability and anti-drying property of the DN ICH were also explored (Figs. 2i, j and S11-S13). After storage for 30 d in an ambient environment, Pre-PMP DN ICH showed significant volume shrinkage owing to water evaporation (Fig. S11), with its weight and conductivity decreasing to 58.19% and 49.92%, respectively. In contrast, PMP DN ICH exhibited relatively higher final weight and conductivity values (81.20% and 66.66%, respectively). The excellent long-term stability and moisture retention of PMP DN ICH were evidently due to the abundant hydrogen bonds in the formed three-dimensional network, which effectively reduced the evaporation rate of internal water [38,39]. Furthermore, the MXene in PMP DN ICH also exhibited excellent oxidation resistance (Fig. S14) [40]. More importantly, PMP DN ICH could be functioned as an effective adhesive material (Fig. S15).

To sum up, the outstanding mechanical performance, environmental resistance, long-term moisture retention ability, conductivity, and oxidation resistance of PMP DN ICH underscore its application potential in flexible wearable electronic device fabrication.

Antibacterial performance plays a critical role to wearable material. Many studies have proved that imidazole-based ILs and MXene possessed outstanding antibacterial performance [41,42]. Therefore, the antibacterial activities of the fabricated PMP DN ICH were verified by using Gram-negative Escherichia coli (E. coli) and Gram-positive Staphylococcus aureus (S. aureus). Figure 3a-c depicts the antibacterial mechanism of the PMP DN ICH. For PIL, the positively charged imidazole rings interacts with the negatively charged phospholipid bilayer of bacterial cell membrane through electrostatic interaction, thus providing an opportunity for imidazole side chain alkyl to insert into the phospholipid bilayer, resulting in the rupture of bacterial cell membrane and the leakage of cytoplasm, thereby killing the bacteria (Fig. 3b) [42,43]. Furthermore, studies have shown that oxygen-containing groups of MXene nanosheets can form hydrogen bonds with lipopolysaccharide chains of the bacterial cell membranes, prevent bacteria from ingesting nutrients, inducing bacteria to produce active oxygen components and cell inactivation, thus inhibiting bacterial growth. In addition, the sharp edges of the MXene nanosheets could also enter the cytoplasmic region by cutting the bacterial cell wall, causing the release of bacterial DNA and eventually disintegrate of the bacteria (Fig. 3c) [44].

The antibacterial ability of the PMP DN ICH is shown in Fig. 3d-f. The sizes of the inhibition zones of the PMP DN ICH against E. coli and S. aureus were found to be 24 and 24 mm (Fig. 3d), respectively, indicating the desirable antibacterial activity of the PMP DN ICH. In addition, E. coli and S. aureus were incubated with the PMP DN ICH at 37 °C for 18 h. The active colonies of all the investigated microbes were almost vanished (Fig. 3e), and the corresponding antibacterial rates of E. coli and S. aureus were found to be 99.91% and 99.98%, respectively (Fig. 3f), further displaying the excellent antibacterial property.

To evaluate the potential applicability of the developed ICH in wearable strain sensing, its electrical sensing properties were comprehensively explored by constructing and assessing a PMP DN ICH-based strain sensor. No obvious signal fluctuations were observed at tensile rates ranging from 50 to 300 mm min⁻¹ and over a tensile strain range of 25%-200%, which demonstrated the reversible and stable signal output ability of the devised strain sensor (Fig. 4a, b). Moreover, the responsive resistance variation waveforms were consistent with the tensile strain (50%), indicating negligible electromechanical hysteresis (Fig. S16) [45]. The stability of the PMP DN ICH-based strain sensor was tested at a tensile strain of 25% over approximately 300 loading-unloading cycles (Fig. 4c). The relative resistance variation was generally consistent, indicating excellent repeatability and stability of the PMP DN ICH-based strain sensor.

Subsequently, the PMP DN ICH-based strain sensor was attached to different parts of the human body to detect human movement (Fig. 4d). Interestingly, when the sensor was mounted on the belly and knee, it readily detected and distinguished between different breathing and motion states (Fig. 4e, f). Furthermore, to achieve remote monitoring of human movement, a wireless sensing system was constructed by connecting a small portable wireless transmission device to PMP DN ICH (Fig. 4g) [8]. The PMP DN ICH-based strain sensor adhered to the neck or wrist could effectively detect neck nodding, looking up movements, and repetitive wrist motion (Fig. 4h, j and Movie S3). More importantly, the relative resistance increased as the bending angle of the finger increased from 30° to 90°, indicating a high sensitivity (Fig. 4i and Movie S4). Additionally, the ability of the wireless sensing system to convey information using Morse codes was explored (Fig. 4g, k) [46]. Distress signals of “GO,” “SOS,” and “HELP” were encrypted and translated by briefly and extensively stretching the PMP DN ICH-based strain sensor in an alternating manner (Fig. 4l-n and Movies S5, S6, S7). The demonstrations of the PMP DN ICH-based wireless strain sensor present the possibility to use PMP DN ICH as wearable devices for human health monitoring, encrypted transmission of information, and human-machine interfaces.

The outstanding temperature resistance of PMP DN ICH was leveraged to use it as a thermosensitive material to explore its viability as a temperature sensor. The thermal sensitivity of a thermistor is commonly evaluated using the temperature coefficient of resistance (TCR), which is estimated using the slope of the fit resistance curves [47]. Therefore, the changes in relative resistance of a PMP DN ICH-based thermistor were monitored with step increases in temperature from 30 to 100 °C (Fig. 5a, b). The obtained TCR values of − 1.96% °C⁻¹ (30-60 °C) and − 0.62% °C⁻¹ (60-100 °C) (Fig. 5b) are superior to most previously reported TCR data (Table S1), demonstrating the outstanding temperature sensitivity of the PMP DN ICH-based thermistor. Furthermore, the PMP DN ICH-based thermistor demonstrated excellent repeatability of the thermal response over relatively small and large temperature ranges (Fig. 5c, d). These results indicated that the PMP DN ICH-based thermistor had excellent thermal sensitivity and could be applied as a thermal sensor for monitoring environmental temperature changes. More importantly, the fabricated thermistor showed remarkable potential in quantitatively monitoring the human body temperature (Fig. 5e, f). For example, the thermistor was fixed onto a mask to detect normal breathing by monitoring the temperature changes during exhalation and inhalation (Fig. 5e). Additionally, when an external heat source was used to simulate the temperature of human fever (Fig. 5f), the thermistor effectively responded to changes in the body temperature through variations in its relative resistance. The above results indicate that the PMP DN ICH-based thermistor is suitable for monitoring the changes in ambient and body temperatures.

To certify the ability of PMP DN ICH to effectively function as an electrolyte, given its unique advantages, a flexible all-solid-state SC was assembled by combining the PMP DN ICH electrolyte exhibiting adhesive properties with an activated carbon electrode (Fig. 6a). The electrochemical performance of the flexible PMP DN ICH-based SC was evaluated by cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) analysis, and EIS. The optimal working potential window of the fabricated SC was determined to be 1.3 V (Fig. S17). As shown in Fig. 6b, the shapes of CV curves were close to rectangle as the scan rate increased from 5 to 100 mV s⁻¹ over the working potential window of 0-1.3 V, exemplifying the typical electronic double layer capacitive performance and excellent rate capability [24,48]. GCD curves of the SC obtained at various current densities (1-8 mA cm⁻²) displayed symmetric triangular shapes and featured a small IR drop even at a high current density of 8.0 mA cm⁻², indicating that the SC exhibited nearly ideal charge-discharge ability and decent capacitive behavior (Fig. 6c) [49]. Notably, even at the highest imposed current density of 8 mA cm⁻², the areal capacitance and coulombic efficiency of the SC were maintained at 143.38 mF cm⁻² and 96.68%, respectively (Fig. 6d). These values are considerably higher than those obtained in previous hydrogel-based studies (Table S2). In addition, the PMP DN ICH-based SC possesses a wide electrochemical window and a range of operating temperatures, which ensure that the SC can be used normally in harsh environments. The EIS curve and the corresponding equivalent circuit of the SC (Fig. 6e) were used to determine its equivalent series resistance (R_s) and charge-transfer resistance (R_ct) from the intercepts of the approximate semicircular area in the high-frequency region of the Nyquist plot [25,30]. The low R_s (5.6 Ω) and R_ct (9.3 Ω) values indicate good electrode-electrolyte contact and the occurrence of efficient charge transfer. Moreover, the data in the low-frequency region were almost parallel to the Z′′-axis, demonstrating the excellent capacitive behavior of the fabricated SC [50]. The Ragone plot suggests that the maximum energy and power densities of the devised SC (55.25 μWh cm⁻² and 5200 μWh cm⁻², respectively) are superior to those of most reported hydrogel-based SCs (Fig. 6f) [2,10,24,48,51,52,53,54,55,56,57]. Furthermore, the fabricated SC retained an initial areal capacitance of 77.08% and an almost unchanged coulombic efficiency of 99.15%, indicating its decent long-term stability (Fig. 6g) [58]. The practical viability of the fabricated SC was assessed by using it to power small electronic devices (Fig. 6h). The SC with a volume of 2 × 1 × 0.3 cm³ was able to drive an electronic meter for 3 min (Movie S8), whereas two SCs connected in series could illuminate an LED bulb for 47 s (Movie S9). These electrochemical results highlight the broad application prospects of the PMP DN ICH-based SC in developing flexible energy-storage systems for wearable electronics.

PMP DN ICH was found to exhibit outstanding mechanical performance, excellent temperature resistance, and long-term stability. Therefore, the electrochemical performance of the PMP DN ICH-based SC was meticulously probed under various conditions (Figs. 7 and S18). The CV curves nearly overlapped as the storage duration increased to 30 d (Fig. 7a). Moreover, the final capacitance retention and coulombic efficiency were 79.93% and 92.78%, respectively (Figs. 7b and S18a), and the Nyquist plots shifted slightly to the right (Fig. 7c), demonstrating the remarkable long-term stability of the SC. The temperature resistance of the SC was investigated by increasing the temperature from − 60 to 80 °C. The CV integration area increased compared to that of the initial state (Fig. 7d), and the R_s value from the Nyquist plots decreased (Fig. 7f) owing to the enhanced ionic diffusion efficiency of the SC at elevated temperatures. Furthermore, the capacitance retention increased gradually from 78.09% to 103.93%, and the coulombic efficiency decreased from 88.79% to 55.56% as the temperature increased from − 60 to 80 °C (Figs. 7e and S18b). The possible reason for this behavior is that with the increasing temperature, the reaction kinetics of some side reactions in the charging process of the supercapacitor accelerated, and the side reaction was prompted to occur at a high temperature, thus extending the charging time of the supercapacitor, resulting in the reduction of its coulombic efficiency [59]. Subsequently, the electrochemical stability of PMP DN ICH under different mechanical stimuli was studied (Figs. 7g-l and S18c, d). Interestingly, the CV curves and Nyquist plots nearly overlapped for different loadings as well as bending angles (Fig. 7g, i, j, l). Moreover, the capacitance retention and coulombic efficiency remained almost unchanged (Figs. 7h, k and S18c, d), indicating the stable energy-storage characteristics of the SC. Overall, the excellent environmental stability, temperature tolerance, and mechanical flexibility of the SC enabled it function as a reliable power source at different temperatures and under varying mechanical conditions. This high-performance PMP DN ICH electrolyte paves a new way for flexible and wearable SCs and could have a wide range of applications in advanced energy-storage devices.

PMP DN ICH was subsequently used as a current collector to assemble a single-electrode-mode TENG (Fig. 8a). An elastomeric silicone rubber substrate (Ecoflex 00-50) was employed as the positive friction layer, a commercial Kapton film was used as the negative-contact triboelectric material layer, and Ag wire was adopted as the electrode [3]. The operating mechanism of the PMP DN ICH-based TENG is illustrated in Fig. 8b. When the Kapton film is separated from the silicone rubber layer, no electric potential is present between the films. However, when the Kapton film touches the TENG, electrons are transferred from the silicone rubber layer to the Kapton film, yielding a positively and negatively charged silicone rubber layer and Kapton film, respectively (Fig. 8b(i)). When the Kapton film is separated and removed, PMP DN ICH provides a negative charge to compensate for the positive charge on the surface of the silicone rubber layer, leading to electron flow from the external circuit to PMP DN ICH (Fig. 8b(ii)). Subsequently, an electrostatic equilibrium is achieved when the Kapton film and silicone rubber layers are completely detached (Fig. 8b(iii)). Once the Kapton film is reconnected to the TENG, electrons are repelled from the PMP DN ICH electrode to ground (Fig. 8b(iv)). Finally, an alternating current (AC) electric signal is generated through continuous contact-separation events.

Typical electrical output measurements of a standard PMP DN ICH-based TENG (40 × 40 mm²; frequency, 2 Hz) were performed under a force load of 2 N. The open-circuit voltage (V_oc), short-circuit current (I_sc), and transferred short-circuit charge (Q_sc) of the devised TENG were 66.0 V, 0.18 μA, and 20.6 nC, respectively (Fig. 8c). The electrical output performance of the PMP DN ICH-based TENG under various frequencies (1-3 Hz) was measured under a force load of 2 N (Fig. 8d). It was found that the V_oc remained relatively stable and reached 67.6 V. Moreover, the TENG could drive loads under different external resistances of 10⁵-10¹⁰ Ω (Fig. 8e), with the optimal output power density being 77.3 mW m⁻² at a load resistance of 2 × 10⁸ Ω. The output voltage stability of the TENG was then monitored for 10,000 contact-separation cycles at a frequency of 2 Hz (Fig. 8f). The superior electrical output reliability indicated that the TENG could satisfy practical application requirements. Subsequently, the TENG was connected to external capacitive loads and LEDs in a commercial rectifier circuit (Fig. 8g). Furthermore, the ability of the TENG to be continuously charged was analyzed at different capacitances (Fig. 8h). Notably, the charging speed accelerated with decreasing capacitance, with the 4.7 and 22 µF capacitors achieving voltages of 5.2 and 1.6 V, respectively, by tapping the device for 200 s at a frequency of 2 Hz. Additionally, the charging ability of the TENG as a power source for real-time practical applications was further assessed by illuminating 68 green commercial LEDs (Fig. 8i and Movie S10), underscoring the significant application potential of the devised TENG for low-frequency mechanical energy harvesting.