Antibacterial Halloysite‐Modified Chitosan/Polyvinylpyrrolidone Nanofibers for Ultrasensitive Self‐Powered Motion Monitoring

High flexibility, porosity, and antibacterial activity are extremely desired for wearable health monitoring, which is beneficial to simultaneously promote wearing comfort and safety. In this study, an antibacterial nanofibers‐based triboelectric generator (AN‐TENG) composed of the flexible chitosan/polyvinylpyrrolidone modified with halloysite nanotubes (CTS/PVP/HNTs) nanofibers and cube‐arrays structured Ecoflex film is proposed for simultaneously energy harvesting and self‐powered human motion monitoring. The open‐circuit voltage (280 V), short‐circuit current (3.98 μA), and transferred charge (51 nC) of the CTS/PVP/HNTs nanofibers TENG at the optimal compound concentration are increased by 90.8%, 86.92%, and 96.2%, respectively, compared to the CTS/PVP nanofibers one (size: 3 cm × 3 cm, mechanical force: 10 N @1 Hz), revealing good real‐time monitoring ability for human wrist, elbow, and finger motion. An antibacterial test is carried out to evaluate the antibacterial activity and the antibacterial rate of the nanofibers against Escherichia coli (ATCC 8739) and Staphylococcus aureus (ATCC 6538) based on the current national standard GB/T 31402–2015, indicating good antibacterial properties of the nanofibers. This research offers an ingenious strategy to establish an antibacterial nanofibers‐based TENG for self‐powered motion monitoring and energy harvesting and offers a new insight to improve the practical security of wearable electronic devices.


Introduction
Wearable healthcare devices enabled by flexible electronics and photonics technology have been devoted to remarkable attraction in human physiological and behavioral monitoring, which are characterized by flexibility, portability, durability, and comfortableness. [1][2][3][4][5] Attaching wearable devices to the cloth or skin can directly obtain signal feedback synchronized with human motion, achieving real-time monitoring of the motion behaviors. As a sustainable energy harvesting device, a triboelectric nanogenerator (TENG) can transfer various kinds of green energy (e.g., wind, wave, vibration, or human mechanical motion) into output electrical signals, which can be beneficial to get rid of the battery power supplies and realize self-powered tactile sensing, [6,7] motion recognition, [8,9] human-machine interfacing, [10,11] and disease diagnosis. [12] Actually, wearable devices are easy to germinate bacteria after long-term contact with human skin, so permeability and antibacterial properties of the materials are highly required. Electrospinning is a promising technique in nanofibrous material fabrication, which is helpful to improve material permeability and reduce bacterial breeding. To further promote wearing comfortableness, porous materials with good skin affinity have been extensively studied through electrospinning technology. [13][14][15] Despite the continuous optimization and improvement of wearable triboelectric devices, the safety and health of the electronic skin were rarely noticed, which will largely hinder its practical application. [16,17] Thus, the antibacterial performance should be a significant prerequisite for TENGs for wearable applications. In recent years, researchers have gradually concentrated on the evaluation of the antibacterial properties of the wearable TENG, while the common flexible antibacterial materials are mainly made by compounding antibacterial fillers, including antibiotics, fluoride, and metal nanoparticles, which lack long-term stability. [18][19][20] To further improve the practicability of the antibacterial TENG, Wang's group proposed a poly(vinyl alcohol)/chitosan (PVA/CTS) nanofibers substrate for self-powered sports sensing, revealing good antibacterial properties toward Escherichia coli and Staphylococcus aureus. [21] The reported antibacterial PVA/CTS nanofibers were only applied as the substrate and more antibacterial triboelectric material can be further developed to improve the triboelectric output and enrich this research field.
Although various flexible materials with good triboelectric characteristics have been extensively researched to improve wearing comfortableness in human motion monitoring, such as MXene/PVA, [9] electrospun micropyramid arrays fabrics (EMPAs), [15] electronic textiles, [16] polypropylene (PP), [17] TiO 2 doped PTFE, [18] polylactic-coglycolic acid (PLGA)/PVA, [19] and bromobutyl rubber (BIIR), [20] further development of flexible materials with good antibacterial and triboelectric property is of great significance to improve the flexibility and lightweight property of the wearable devices for human motion monitoring. As a kind of natural biopolymer material, the good antibacterial activity of CTS can be attributed to the protonation of the primary amino groups on the molecular chain in a dilute acid solution, resulting in a large amount of positive charges that can interact with the negatively charged bacterial surface. [22,23] In addition, CTS can act as a typically triboelectricpositive material because the protonated amino groups and acetic acid might be positively charged in the triboelectric series, while researchers are mainly concentrating on the effect of dilution ratio in acetic acid to find out the optimal triboelectric outputs of the CTS film. [24][25][26][27] To obtain porous CTS film with air permeability, PVA, polyethylene oxide (PEO), and polyvinylpyrrolidone (PVP) are usually used as the spinning aids during the electrospinning process because it is hard to prepare the pure CTS nanofibers due to the repulsive forces between ionogenic groups. [28] Meanwhile, the triboelectricpositive property of CTS can be further enhanced when a hydrogen-bonded network is formed between CTS and other materials rich in oxygen functional groups. [29] Thus, constructing porous CTS-based composite nanofibers can offer a new opportunity to fabricate wearable devices simultaneously holding antibacterial, flexible, and high electrical output properties.
PVP as a non-ionogenic material has been regarded as an ideal partner for the electrospinning of CTS in the biomedical field due to its biocompatibility, non-toxicity, and good complexation properties. [28,30] Moreover, halloysite nanotubes (HNTs) hold hol-low nanostructure, high surface area, mechanical and chemical stability, functionalization potential, biocompatibility, and low cost, which are suitable for the fabrication of biocompatible wearable sensors. [31][32][33][34] The previous reports have demonstrated that the addition of HNTs can help to enhance the surface roughness of the nanofibers, [35][36][37] which should be a desired material to further improve the triboelectric charge density of the nanofibers. Thus, it will be of great research significance to investigate the influence of HNTs on the triboelectric outputs of the CTS-based nanofibers TENG. Featured with high elasticity, skin affinity, easy preparation of surface microstructure, simple preparation process, and low cost, Ecoflex is usually applied as a triboelectricnegative material in high-performance TENG fabrication, and it can effectively improve the output of TENG by constructing microstructures or metasurfaces. [1,25] In this work, different concentrations (0, 2, 5, 8, and 10 mg mL −1 ) of HNTs were applied to regulate the morphology and triboelectric output of the CTS/PVPbased nanofibers during the electrospinning process. An antibacterial CTS/PVP/HNTs nanofibers-based TENG (AN-TENG) was fabricated by integrating a cube-arrays structured Ecoflex film of the CTS/PVP/HNTs nanofibers, and the AN-TENG with 2 mg mL −1 of HNTs concentration holds the best outputs. Antibacterial test results demonstrate that the antibacterial activity and the antibacterial rate of the CTS/PVP/HNTs nanofibers sample against E. coli (ATCC 8739) are 5.27 and 99.9995%, while that against S. aureus (ATCC 6538) are 5.13 and 99.9993%, indicating that the as-prepared CTS/PVP/HNTs-2 film holds good antibacterial properties against both gram-negative bacteria and grampositive bacteria. Furthermore, the open-circuit voltage, shortcircuit current, and transferred charge of the AN-TENG have been increased by 90.8%, 86.92%, and 96.2%, respectively, compared to the CTS/PVP device. The AN-TENG reveals a peak power density of 0.73 W m −2 at a load resistance of 100 MΩ, an excellent sensitivity of 10.89 (V/N) toward 1 to 15 N, and good real-time monitoring ability for human wrist, elbow, and finger motion. This work provides a novel strategy to develop an excellent triboelectric nanofibers film with great antibacterial properties and offers a new insight to improve the practical security of wearable electronic devices. Figure 1a illustrates the fabrication process of the antibacterial CTS/PVP/HNTs nanofibers through the electrospinning method. Briefly, different concentrations (0, 2, 5, 8, and 10 mg mL −1 ) of HNTs were added into CTS/PVP mixture solution to promote the mechanic property and surface roughness of the nanofibers, which were marked as CTS/PVP, CTS/PVP/HNTs-2, CTS/PVP/HNTs-5, CTS/PVP/HNTs-8, and CTS/PVP/HNTs-10, respectively. During the electrospinning process, DC voltage (18 kV), nozzle and collected aluminum substrate distance (12 cm), solution feed rate (10 L min −1 ), feed time (2 h), and working temperature (40°C) were fixed to prepare the five kinds of nanofibers. As a typical triboelectronegative material, Ecoflex holds an extremely good ability to acquire electrons from most other materials. To further improve the surface triboelectric charge density, the cube arrays structured Ecoflex film was constructed by template imprinting method ( Figure 1b). First, a Si template with cube groove arrays was prepared through photolithography and ion beam etching process. The feature size of each cube and the gap between two cubes were fixed at 50 m and the whole pattern size was 3 cm × 3 cm. A layer of release agent was sprayed on the surface of the Si template, then dry the template at 70°C for 30 min on the hot plate. The microstructured Ecoflex film was prepared by the following four processes: mixing components A and B of Ecoflex at a volume ratio of 1:1, stirring and vacuuming to get uniform mixing and remove solution bubbles, coating on the Si template and drying at 60°C for 30 min on the hot plate, and peeling off from the template to obtain a microstructure film. Figure 1c-h illustrates the field emission scanning electron microscope (FESEM) images of the CTS/PVP, CTS/PVP/HNTs-2, CTS/PVP/HNTs-5, CTS/PVP/HNTs-8, and CTS/PVP/HNTs-10 and micro cube structured Ecoflex film at a different magnification of i) 20 000 and ii) 50 000. Figure 1c,d indicates the randomly oriented uniform fibers at the HNTs addition concentration of 0 and 2 mg mL −1 . It can be clearly seen that HNTs nanotubes are coated on CTS/PVP nanofibers, making the smooth surface become rough, which is beneficial to simultaneously enhance the mechanical strength and surface roughness of the CTS/PVP nanofibers. [36,37] As for the CTS/PVP/HNTs-5 sample (Figure 1e), more HNTs are coated on the CTS/PVP nanofibers, while the nanofibers uniformity and the minimum nanofiber diameter has been decreased due to the influence of HNTs addition on the solution state of CTS/PVP. The CTS/PVP/HNTs-8 sample (Figure 1f) shows a little fracture in the nanofibers. Seriously broken CTS/PVP nanofibers can be observed (Figure 1g) when the HNTs concentration is enhanced to 10 mg mL −1 , which can be attributed to the agglomeration of the HNTs in clumps attributed along the nanofibers. Figure 1h demonstrates the uniformly distributed microcube structure of the Ecoflex film with an average size of 56 m. From Figure 1hii and Figure S1d, Supporting Information, a lot of folds are formed on the material surface due to the peel-off process, which can further promote the surface roughness and triboelectric charge density. Figure 2a shows the EDS elemental mapping images of the CTS/PVP/HNTs-2 nanofibers (2 mg mL −1 HNTs), displaying the proper distribution of the Al, Si, O, C, and N elements. According to the molecular structure of CTS, PVP, and HNTs, the appearance of Al and Si element should be derived from HNTs, demonstrating the successful addition of HNTs into the CTS/PVP nanofibers.

Results and Discussions
The antibacterial properties of the CTS/PVP/HNTs-2 nanofibers against E. coli (ATCC 8739) and S. aureus (ATCC 6538) were tested by the Chengdu Ceshigo Research Service Center, where all the test conditions are based on the current national standard GB/T 31402-2015. [38,39] The initial bacteria suspension concentration of E. coli is 8.9 × 10 5 CFU/mL and that of S. aureus is 8.7 × 10 5 CFU/mL, which can meet the standard test requirements. [38] After culturing for 24 h, all samples were recovered immediately by adding 10 mL of SCDLP culture solution to the petri dish and rinsing the sample thoroughly, and then counting the colonies to evaluate the antibacterial properties. The average number of viable bacteria immediately tested after inoculation is represented by U 0 . According to the test results, U 0 of the E. coli is 2.2 × 10 4 CFU/cm 2 and that of the S. aureus is 2.1 × 10 4 CFU/cm 2 . As displayed in Figures 2b,c, the E. coli colony of the three control groups is 37, 40, and 39 after  24 h bacterial culturing, while that of the three CTS/PVP/HNTs-2 films is 1, 2, and 2, respectively. As depicted in Figure S2, Supporting (1) and (2), [28,38] where M is the average number of the surviving bacteria cells of the three control samples on the plates after 24 h culturing, and N is that of the tested three CTS/PVP/HNTs nanofibers, respectively. In addition, U t and A t are the logarithm of M and N, respectively. [38] The calculated antibacterial activity of the CTS/PVP/HNTs-2 nanofibers against E. coli (ATCC 8739) is 5.27, and that against S. aureus (ATCC 6538) is 5.13. The calculated antibacterial rate of the CTS/PVP/HNTs-2 nanofibers against E. coli (ATCC 8739) is 99.9995%, and that against S. aureus (ATCC 6538) is 99.9993%. Thus, the antibacterial test results demonstrate that the as-prepared CTS/PVP/HNTs-2 film holds good antibacterial properties against both gram-negative bacteria and gram-positive bacteria. The good antibacterial activity of CTS/PVP/HNTs-2 nanofibers mainly derives from the amino groups of CTS and abundant hydrogen-bonded networks between CTS, PVP, and HNTs will further improve the electron-donor functionalities of the nanofibers leading to a large amount of surface positive charges that can interact with the negatively charged bacterial surface. [28,29] Antibacterial rate (%) = (M − N)∕M × 100% (1) To investigate the application potential in the field of energy harvesting and self-powered human motion monitoring, the CTS/PVP/HNTs-2 nanofibers and cube arrays structured Ecoflex film were integrated to fabricate an AN-TENG. As depicted in Figure 3a, a back Al electrode (thickness: 100 m) has been attached to the back of micro-structured Ecoflex film and connected to the ground. A thin PET package layer (thickness: 100 m) can maintain a certain distance between the nanofibers and the Ecoflex. Due to the good flexibility and resilience of PET film, the AN-TENG can achieve contact and separation states under the pressing and releasing of mechanical force such as human hand tapping. Figure 3bi-iv illustrates the working principle of the as-prepared AN-TENG, which is consistent with the singleelectrode working mode. Briefly, when the two triboelectric materials contact with each other by environmental mechanical force, an equal amount of positive and negative triboelectric charges can be formed in the CTS/PVP/HNTs-2 and Ecoflex, respectively, owing to the great difference in electron affinity, as shown in Figure 3bi. Once release the force, an electric potential difference can be established between the two layers, and electrons will flow from the back electrode of Ecoflex to the ground to maintain charge balance (Figure 3bii). When the separation distance is far enough, an electrical equilibrium will be formed and there is no electron movement in the external circuit (Figure 3biii). During the contact process, a new electric potential difference will drive the electrons flowing from the ground to the back electrode of Ecoflex, forming an opposite current in the external www.advancedsciencenews.com www.advsensorres.com circuit. To further instigate the working mechanism of the asfabricated single-electrode-based AN-TENG, finite element simulation has been implemented to explore the device's electric potential through COMSOL software. As shown in Figure S3a, Supporting Information, the constructed model is based on an Ecoflex film (thickness: 1 mm) attached with a grounded Al electrode (thickness: 150 m) and a CTS/PVP/HNTs film (thickness: 100 m). Considering the miniaturized design of the wearable device, the gap between the tribopairs was set to change from 0 to 6 mm with a step of 0.5 mm in the simulation process, as shown in Figure S3a, Supporting Information. The triboelectric charge density on the CTS/PVP/HNTs film and Ecoflex film was assigned as 1 and −1 C m −2 , and the permittivity of the two triboelectric materials was set as 2.6 and 3.4, respectively, according to the reported references. [40][41][42] Figure S3b-e, Supporting Information, depicts the calculation results of the electric potential distribution with the tribopairs gap of 0, 2, 4, and 6 mm. As displayed in Figure S3f, Supporting Information, the potential difference between the tribopairs is increasing with the increase of the gap distance, which indicates a similar regular with the reported reference. [43,44] Figure 3c-e displays the open circuit voltage, short-circuit current, and transferred charge of the TENG based on five nanofibers with different HNTs concentrations driven by a fixed mechanical force at 10 N with a frequency of 1 Hz.
With the appropriate addition of HNTs into the CTS/PVP, the output electrical signals have been effectively improved. The CTS/PVP/HNTs-2 nanofibers-based TENG holds the optimal performance, and the voltage (280 V), short-circuit current (3.98 A), and transferred charge (51 nC) have been increased by 90.8%, 86.92%, and 96.2%, respectively, compared to the CTS/PVP device (152 V, 2.14 A, 26 nC). From the FE-SEM analysis results, with the increase of the HNTs concentration, the surface roughness will be promoted but the quality of the CTS/PVP nanofibers will be declined. Thus, there might be a balance between the two factors. It can be clearly seen from Figure S5, Supporting Information, that the output performances of the CTS/PVP/HNTs-5 and CTS/PVP/HNTs-8 nanofibers-based TENG are obviously improved, while that of the CTS/PVP/HNTs-10 nanofibers based TENG is severely decreased. Based on the test results, CTS/PVP/HNTs-2 film is used in the following device fabrication.
To further investigate the influence of driven frequency on the output performances of the AN-TENG, outputs under different driven frequencies ranging from 0.5 to 5 Hz at a fixed mechanical force of 10 N have been evaluated.  Figure S4, Supporting Information, the variation curves of output signals via different frequencies indicate that the increasing rate of the voltage and charge slows down when the frequency is beyond 3 Hz, showing a saturated trend. Outputs of the AN-TENG driven by different mechanical forces ranging from 1 to 60 N at a fixed frequency of 1 Hz were measured to explore the application potential of the AN-TENG as a pressure sensor. Figure 4d-g indicates that the output voltage, current, and charge are increasing with the increase of the driven force. In detail, the voltage, current, and charge change from 167 to 433 V, 1.44 to 7.25 A, and 27.82 to 77.80 nC, respectively, within a force range of 1-60 N, and the saturated outputs of the as-fabricated AN-TENG are higher than that of most reported CTS-based TENGs. [19,25,27,29] As shown in Figure 4h, the voltage-force fitting curve of the AN-TENG demonstrates a good linearity (R 2 = 0.9838) and an excellent sensitivity of 10.89 (V/N) ranging from 1 to 15 N, indicating a great application potential in ultrasensitive triboelectric pressure sensor to achieve selfpowered sensing. Finally, output voltage comparison between CTS/PVP/HNTs-2 nanofibers film and other materials (PE and some typical triboelectricpositive materials like Al, nylon, and cellulose paper) has been carried out by fixing the Ecoflex layer to evaluate the triboelectric property of the nanofibers. Test results demonstrate that the as-fabricated CTS/PVP/HNTs-2 holds better triboelectricpositive properties than the normal triboelectricpositive materials, which may be attributed to the rough surface promoted by the appropriate addition of HNTs.
The output performance of the AN-TENG is systematically researched by measuring the maximum peak power under the matching load resistance and the charging behavior for the capacitors. Figure S6, Supporting Information, displays the opencircuit voltage and short-circuit current of the AN-TENG, indicating uniform output waveforms. Continuous output voltage within 40 000 working cycles demonstrates good long-term mechanical stability of the AN-TENG ( Figure S7, Supporting Information). Figure 5a indicates the dependence of the peak-to-peak output voltage, current, and power density on the external loading resistance, in which the peak power density can reach 0.73 W m −2 at 100 MΩ driven by a fixed mechanical force of 10 N at 1 Hz. As displayed in Figure 5b and Video S1, Supporting Information, the AN-TENG can instantaneously light up 100 light-emitting diodes (LEDs). Subsequently, the energy harvesting ability of the AN-TENG has been measured by charging different capacitors and acting as the power source of the electronic equipment. Figure 5c shows the schematic circuit diagram of the charging capacitor and drive electronics and the AN-TENG can charge the 1.1, 2.2, 4.7, and 10 F capacitors to 17.8, 9.6, 5.2, and 4.4 V, respectively, within 180 s, implying the great potential to act as the power source for driving electronics.
Due to the good flexibility and resilience of PET film, the AN-TENG can be easily driven by human hand tapping. As shown in Video S2 and Figure S8, Supporting Information, the peak-topeak output voltage of the AN-TENG with a 5 GΩ load resistance can reach 180 V until the upper and lower materials fully contact. Subsequently, the charging and discharging curves of the capacitors driven by hand tapping display the turning-on process of six LEDs, a commercial timer, and a thermo-hygrometer, respectively. Figure 6a depicts that the AN-TENG can be used to charge the 2.2 F capacitor to 13 V within 180 s by fast hand tapping, and the discharging process of the capacitor can light up the LEDs (Video S3, Supporting Information). Furthermore, a similar process can be carried out to charge a 10 F capacitor to 2-2.5 V within 2 min to turn on the commercial timer (Figure 5b and Video S4, Supporting Information) and thermo-hygrometer (Figure 5c).
Owing to the excellent antibacterial property of the CTS/PVP/HNTs-2 nanofibers, it is beneficial to inhibit the growth of bacteria when the nanofibers are attached to the skin or cloth during the fabrication of some wearable electronic devices. As illustrated in Figure 6d, a simple flexible bending antibacterial nanofibers-based TENG (FBAN-TENG) was fabricated by bending and fixing the bottom CTS/PVP/HNTs-2 nanofibers and upper Ecoflex film with a certain gap. Due to the better elasticity of the upper layer, the wearable FBAN-TENG (3 cm × 3 cm) can be applied to monitor various human activities such as wrist bending, elbow movement, and finger bending. Figure 6e and Video S5, Supporting Information, show the real-time monitoring of the wrist bending at different angles ranging from 0°to 90°. The same FBAN-TENG can be also used to monitor elbow movement, as shown in Figure 6f and Video S6, Supporting Information. A smaller FBAN-TENG with a size of 1.5 cm × 2 cm can be attached to the finger (Figure 6g and Video S7, Supporting Information), indicating an ultrasensitive sensing ability for the finger bending motion track.

Conclusions
In conclusion, a novel wearable AN-TENG was developed by combing the antibacterial CTS/PVP/HNTs nanofibers with cube-arrays structured Ecoflex film for energy harvesting from human activity and real-time monitoring of different motion states. Antibacterial test results indicate that the CTS/PVP/HNTs-2 nanofibers hold high antibacterial activity and antibacterial rate against E. coli (ATCC 8739) and S. aureus (ATCC 6538), demonstrating good antibacterial properties against both gram-negative bacteria and gram-positive bacteria. The concentration of HNTs displayed an obvious regulating function of the nanofiber's morphology and roughness, and the existence of HNTs effectively enhanced the output voltage, current, and transferred charge of the AN-TENG, showing a maximum peak power density of 0.73 W m −2 at 100 MΩ driven by a fixed mechanical force of 10 N at 1 Hz. In addition, the AN-TENG can instantaneously light up 100 LEDs and charge the 1.1, 2.2, 4.7, and 10 F capacitors to 17.8, 9.6, 5.2, and 4.4 V, respectively, within 180 s. Moreover, the AN-TENG can be used to charge the 2.2 F capacitor to 13 V within 180 s and charge the 10 F capacitor to 2-2.5 V within 2 min by fast hand tapping, and the discharging process of the capacitor can light up the LEDs and turn on the commercial timer and thermo-hygrometer. Finally, an FBAN-TENG was proposed to realize real-time monitoring of human motion like wrist,  elbow, and finger bending. This research provides novel antibacterial nanofibers with excellent triboelectricpositive properties, which indicates an ingenious strategy to establish an antibacterial nanofibers-based TENG for self-powered motion monitoring and energy harvesting, which is beneficial to improve the comprehensive performance of wearable electronic devices.
Fabrication of the CTS/PVP/HNTs Nanofibers: To obtain high-quality nanofibers through the electrospinning process, CTS and PVP were mixed in a mass ratio of 2:8 and then dissolved in 90% (v/v) acetic acid to get the 8% (w/v) CTS/PVP mixture solution by vigorous stirring for 4 h under room temperature. To further investigate the effect of HNTs addition on the triboelectric characteristics of CTS/PVP nanofibers, a certain amount of HNTs were uniformly mixed in PVP/CTS solution with the concentration of 2, 5, 8, and 10 mg mL −1 . After that, the obtained solutions were transferred into a syringe for further electrospinning process. The parameters for electrospinning were set as follows: applied DC voltage: 18 kV, distance between nozzle and collected aluminum substrate: 12 cm, solution feed rate: 10 L min −1 , feed time: 2 h, working temperature: 40°C. A schematic illustration of the fabrication process can be found in Figure 1a. The five kinds of nanofibers were labeled as CTS/PVP, CTS/PVP/HNTs-2, CTS/PVP/HNTs-5, CTS/PVP/HNTs-8, and CTS/PVP/HNTs-10, respectively.
Fabrication of the Micro-Structured Si Template: To fabricate the cube arrays structured Ecoflex film, a Si template with cube groove arrays was prepared through photolithography and ion beam etching process. As shown in Figure S1a, Supporting Information, the square array pattern with a whole size of 3 cm × 3 cm was designed by the software of CleWin, and the feature size of each cube and the gap between the two cubes were fixed at 50 m. The Si wafer was cut into 4 cm × 4 cm followed by ultrasonic cleaning with deionized water, acetone, and ethanol for 20 min, respectively. As illustrated in Figure 1b, a layer of NR9-3000 PY was spincoated on the Si wafer at 3000 rpm for 30 s. Subsequently, used a hot plate at 150°C for 60 s to complete the soft-bake process. After UV exposure of 55 s through a UV lithography machine, baking at 100°C for 60 s and developing in the developer for 15 s, the photoresist at the square pattern shall be removed. Finally, the square pattern was etched by an ion beam etching machine to obtain the cube groove template. Figure S1b,c displays the optical photograph and optical microscope diagram of the micro-structured Si template, demonstrating a uniform distribution of square groove structure.
Fabrication of the Cube Arrays Structured Ecoflex Film: A layer of release agent was sprayed on the surface of the Si template, then dried the template at 70°C for 30 min on the hot plate. The components A and B of Ecoflex were mixed at a volume ratio of 1:1, then stirred the mixture until uniform mixing. After that, the mixture was vacuumed to remove solution bubbles. The Ecoflex solution was coated on the as-prepared Si template and dried at 60°C for 30 min. Eventually, the Ecoflex film was peeled off from the template to obtain a microstructure film (Figure 1b).
Fabrication of the Antibacterial Nanofibers-Based Triboelectric Nanogenerator: The flexible CTS/PVP/HNTs nanofibers and cube arrays structured Ecoflex film with a back Al electrode (thickness: 100 m) were packaged through a layer of PET film (thickness: 100 m), as illustrated in Figure 3a. The whole device size was 3 cm × 3 cm.
Antibacterial Test: The antibacterial properties of the CTS/PVP/HNTs-2 nanofibers against E. coli (ATCC 8739) and S. aureus (ATCC 6538) were tested by the Chengdu Ceshigo Research Service Center, where all the test conditions were based on the current national standard GB/T 31402-2015. [38,39] Before testing, three CTS/PVP/HNTs-2 nanofiber films were cut into 4 cm × 4 cm for three groups of parallel experiments, while the sterile medical PE films without antibacterial properties were applied as the control groups. During the measurement process, a sterile inoculation loop was used to transfer a loop of precultured bacteria to a small amount of nutrient broth and diluted it to make sure that the initial bacteria concentration ranged from 2.5 × 10 5 to 10 × 10 5 CFU mL −1 . [38] The tested films were put on the sterile glass plate after UV radiation sterilization for 30 min, then 400 L bacteria suspension with a suitable concentration was evenly seeded on the surface of the tested films by pipette. After culturing for 24 h, all samples were recovered immediately by adding 10 mL of SCDLP culture solution to the petri dish and rinsed the sample thoroughly and then counted the colonies to evaluate the antibacterial properties.
Characterization and Measurement: The morphologies of the CTS/PVP/HNTs nanofibers and micro-structured Ecoflex film were characterized by the SEM (FEI Inspect F, 20 kV). The output voltage of the AN-TENG was measured by a Keithley 6517 system electrometer combing with a Keysight 34470 digital multimeter for high-speed data acquisition. The output current and transferred charge of the AN-TENG were measured through Keysight 2985B electrometer. All the electrical output measurements were carried out at room temperature of 25°C and the environmental humidity was controlled by a dehumidifier to maintain around 40% RH. All the participants affirmed their consent to report the related experiment results of the wearable tests in this work including human activities monitoring like wrist bending, elbow movement, and finger bending.

Supporting Information
Supporting Information is available from the Wiley Online Library or from the author.