Highly stretchable triboelectric tactile sensor for electronic skin

Highly stretchable triboelectric tactile sensor for electronic skin

Accepted Manuscript Highly stretchable triboelectric tactile sensor for electronic skin Yu Cheng, Dan Wu, Saifei Hao, Yang Jie, Xia Cao, Ning Wang, Zh...

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Accepted Manuscript Highly stretchable triboelectric tactile sensor for electronic skin Yu Cheng, Dan Wu, Saifei Hao, Yang Jie, Xia Cao, Ning Wang, Zhong Lin Wang PII:

S2211-2855(19)30614-7

DOI:

https://doi.org/10.1016/j.nanoen.2019.103907

Article Number: 103907 Reference:

NANOEN 103907

To appear in:

Nano Energy

Received Date: 11 June 2019 Revised Date:

7 July 2019

Accepted Date: 13 July 2019

Please cite this article as: Y. Cheng, D. Wu, S. Hao, Y. Jie, X. Cao, N. Wang, Z.L. Wang, Highly stretchable triboelectric tactile sensor for electronic skin, Nano Energy (2019), doi: https:// doi.org/10.1016/j.nanoen.2019.103907. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

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Graphical Abstract

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Highly Stretchable Triboelectric Tactile Sensor for Electronic Skin Yu Chenga,b,#, Dan Wuc,#, Saifei Haoa,b,#, Yang Jiea,b,#, Xia Cao a,b,c,d,*, Ning Wangc,*, and Zhong Lin

a

Beijing Institute of Nanoenergy and Nanosystems, Chinese Academy of Sciences, National Center

for Nanoscience and Technology (NCNST), Beijing 100083, China. b

College of Nanoscience and Technology, University of Chinese Academy of Sciences, Beijing

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100049, China. c

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Wanga,b,d,e,*

Research Center for Bioengineering and Sensing Technology, Beijing Key Laboratory for

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Bioengineering and Sensing Technology, School of Chemistry and Biological Engineering, Beijing Municipal Key Laboratory of New Energy Materials and Technologies, and Center for Green Innovation, School of Mathematics and Physics, University of Science and Technology Beijing, Beijing 100083, China. d

Nanning, 530004, China. e

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Center on Nanoenergy Research, School of Physical Science and Technology, Guangxi University,

School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia

30332, USA.

*

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whom

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# Authors contributed equally to this work. correspondence

should

be

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[email protected]; [email protected]

1

addressed,

E-mail:

[email protected];

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Abstract: Tactile sensing is one of the key technologies for robotics that enables recognition of vibrations and brief moments of contact with an object, and facilitating object-manipulation and recognition.

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Here we describe a fabrication of highly efficient triboelectric nanogenerator that enables high yield and uniformity from stretchable electronic polymers with controlled density of tactile sensors, which thus constitute intrinsically self-powered stretchable (up to 580%) skin electronics. A dynamic pressure can be harnessed and detected with a sensitivity of 0.04 µA/KPa in the linear range from 16

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KPa to 64 KPa and the texture and hardness of the object can be read out from the current waveforms with a location detection sensitivity of 2 mm, which help robots determine the moment

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and assess the grasp stability when they first come in contact with an object. Meanwhile, temperature can be detected in the linear range from 19.4 ℃ to 34.9 ℃ with a sensitivity of 0.59 µA/℃. At the same time, mechanical energy can be harnessed and converted to electricity with an open-circuit voltage of 160 V, a short-circuit current of 12.4 µA, and a maximum out power of 1387 µW (0.087 mW/cm2). Our process offers a general strategy for the fabrication of next generation stretchable

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TENG toward the development of self-powered skin electronic devices from robotics to the medical field, consumer devices and the auto industry.

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Keywords: Tactile sensor, Multimodal, Triboelectric nanogenerator, Self-powered, Flexible

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1. Introduction Soft tactile sensors that can be set to merge with our bodies which integrated senses for stress sensing, temperature sensing, humidity sensing are highly desirable for applications such as health

interactions.[1, 2]

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monitoring, biological researches, and robotic technologies that involve in-depth human–machine Rendering such electronics self-powered and stretchable would make them more

comfortable, reliable, and sustainable to wear. Now structural engineering has enabled us fabricating soft sensors with high mechanical deformability and robustness by using intrinsically stretchable

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polymer materials. However, such fabrication process always involves sophisticated fabrication process and suffers the lack of a scalable fabrication of high yield and uniformity. Considering their

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enormous potential to extend our perceptions, such as skin-like sensors that can measure pressure, strain and temperature are highly desirable to monitor body movements and health conditions. Energy module plays a dominant role in the application of flexible electronic skin. In the past few hundred years, fossil energy and the electricity derived from it have dominated the supply of human beings.

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Triboelectric nanogenerator (TENG) is a burgeoning technology of energy conversion that was first invented by Wang’s group in 2012[3] by conjugation of triboelectrification and electrostatic induction.[4] It can convert majority of forms of mechanical energy into electrical energy even at

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very low frequencies. In addition, TENG has the advantages of low-cost, easy assembly and high output voltage. TENG can be applied to a wide range of emerging fields through extensive research by researchers.[5-9] For example, wireless energy delivery,[10, 11] energy harvesting,[12-15]

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flexible electronics,[16-23] self-powered systems,[24-28] implantable medical devices[29-31] and so on. Interestingly, TENGs produce a voltage in response to mechanical deformation, which can be used to measure the magnitude of dynamic forces and mimic the properties of FA-I and FA-II receptors. Because they can produce electric energy during mechanical stimulation, they have additional advantages for self-powered applications with a much simpler structure. For example, they can act as simultaneously the stretchable sensor and the matching energy harvesting devices, which are the core technologies of the soft electronics. Either woven into our clothing, worn on our skin or implanted in our bodies, TENGs made of stretchable polymers could be stretched mechanically and 3

ACCEPTED MANUSCRIPT are rubust from wear and tear. At the same time, they can harvest energy from motion while solar cells are ineffective under clothing. The power output is enough for charging stretchable batteries. [32-34] Herein, a highly stretchable TENG-based triboelectric sensor has been designed for electronic

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skin by a convenient inorganic modification method with a stretchability and simplicity that greatly surpass those achieved by other approaches. To highlight its versatility, we use this platform to demonstrate various intrinsic sensing ability ranging from dynamic force, temperature, and location detection, demonstrating its potential to finally bring about self-powered skin electronic systems with

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its stretchability enabled by intrinsically stretchable materials. Our fabricated stretchable sensor not only convert mechanical energy into electrical energy, but also detect dynamic force in the linear

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range of from 16 KPa to 64 KPa with a sensitivity of 0.04 µA/KPa. Interestingly, the texture, hardness, as well as the location of the object can be read out from the waveform with a precision of 2 mm. Therefore, this self-powered flexible electronic skin based on TENG has broad application prospects, such as the intelligent mechanical arm, touch screen, position sensing and so on.

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2. Results and Discussion

The triboelectric sensor is based on a single electrode TENG (STENG), as shown in Figure 1a. The top part is a kind of functional film that is made up of polydimethylsiloxane (PDMS) and

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organo-montmorillonite-cetyltrimethylammonium bromide (OMMT-CTAB). The films were prepared by solution intercalation technique. The CTAB was intercalated into OMMT layers forming OMMT-CTAB (modified OMMT) (Figure 1b). Four silver nanowires with a diameter of 200 nm and

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a length of 25 μm (Figure 1c) as electrodes were placed on the surface of the hybrid elastomer film. The copper film was directly contacted with silver nanowires forming composite electrodes. A grid of ZnO NWs (Figure 1d) was fabricated to produce a device that patterned substrate was positioned over the film. Using the stretchable of elastomer, the device is also ultra-stretchable. To test the mechanical properties of the PDMS/OMMT-CTAB-STENG (PO-STENG), a uniaxial stretching test was performed as described in Figure 1e by an ESM301/Mark-10 system. The initial state of PO-STENG as shown in Figure 1e (λ=L/L0=1, L0 is the initial state, and L is the stretched state), the length of the 4

ACCEPTED MANUSCRIPT device increased with the force increased when an outside force was applied to it. Figure 1f exhibits the picture of the PO-STENG when λ=5.8 to show the good tensile property of the triboelectric sensor. When released the tensile force, the PO-STENG could almost completely recover its original shape. Therefore, it can be considered that the stretchability and strength of the PO-STENG are

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tunable by selecting the appropriate proportion of OMMT-CTAB and PDMS. It is inferred that the PDMS macromolecular chain in the filled film is inserted between the montmorillonite silicates and cross linked by vulcanization, which makes the montmorillonite silicates and the polymer matrix form an indivisible whole. When the polymer matrix is subjected to external force, the silicate layer

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can transfer and share the stress and hinder the further development of the craze, so as to realize the

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reinforcement of the film.

Figure 1. .Structural design of the PO-STENG. (a) Schematic diagram of the PO-STENG. (b) SEM image of the morphology of the elastomer, the inset shows the photograph of the PO-STENG. (c) SEM image of the Ag nanowires. (d) SEM image of the ZnO nanowires. (e) Uniaxial tensile test 5

ACCEPTED MANUSCRIPT of the PO-STENG. (f) The stretched state (stretch λ=5.8) of the PO-STENG. The proportion of OMMT-CTAB produces an effect on the output performance of the PO-STENG, as well as the tensile strength and elongation at break of the film. The output performance of the devices with different weight ratios of OMMT-CTAB was explored under a

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frequency of 2 Hz by a linear motor as shown in Figure 2a. Eight groups of samples were compared the output voltage and current of the PO-STENG device with the same area of 4 cm×4 cm under the coincident applied force. It can be clearly seen that the output performances of PDMS-STENG (without OMMT-CTAB) are obviously lower than the PO-STENG with different ratios of

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OMMT-CTAB (lower than 12%). The short circuit current increases from nearly 4.0 μA to 14.2 μA

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and voltage increases from 55 V to 160 V. After surface organic modification, montmorillonite is easily dispersed uniformly in the polymer, and the hydrophobicity of the film surface is also significantly improved (Figure 2a insets). But when the amount of OMMT-CTAB is excess (higher than 12%), the homogeneity of the film is destroyed because of the aggregation of the OMMT in the membrane, which leads to the relative decrease of the output signal of the PO-STENG. Therefore, 4

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wt% of the OMMT-CTAB is the best mass ratio to reach the maximum output signal. Based on this

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proportion, OMMT-CTAB was mixed in the PDMS, fabricated a composite film.

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Figure 2. . Electrical output of the PO-STENG. (a) The output of the PO-STENG with different OMMT-CTAB concentration. Insets show the change of water droplet profile. (b) Transferred charges of as-prepared PO-STENG. (c) Open circuit voltage of the PO-STENG. (d) Short circuit

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current of the PO-STENG. (e) Short circuit current of the PO-STENG with different size of area. (f) The relationship between the short circuit current of PO-STENG and the applied pressure.

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The transferred charges and open voltage of the PO-STENG (4%, 4 cm×4 cm) are shown in Figure 2b, c. The charges are up to 45 nC while the open voltage is 160 V and the short circuit current is 12.4 μA (Figure 2d). A test that research the effect of contact area on device performance has also been done. As the contact area increases, the short circuit current also increases (Figure 2e). The short circuit curent of the device, which is 1 cm×1 cm, is 3.5 μA while it is 20 μA of the 6 cm× 6 cm one. The reason for this phenomenon is that devices with large areas have more opportunities to contact with the rough structure on the surface of the film. At the same time, the ZnO nanowires in the middle of the film and the film will create friction at the nanoscale to generate charges. This will 7

ACCEPTED MANUSCRIPT increase the current output of the device. Similarly, a test that research the effect of applied pressure on the output performance of PO-STENG was done. Figure 2f shows that as the applied pressure increases, the output current of the device increases linearly. When the applied pressure increases from 16 KPa to 64 KPa, the output current increases from less than 1 µA to 2.9 µA. This proves that

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the device has a good linear pressure sensing function with a sensitivity of 0.04 µA/KPa. Next, the effect of working frequency on the output performance of PO-STENG was studied by using a linear motor to control the speed of the object. As we can see from the Figure S1 and S2, in the working frequency range from 1 Hz to 5 Hz, the short circuit current peak value of the device increases

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linearly and the number of peaks also increases within the same time, the output current value increases from 5 µA to 20.2 µA. By the method of linear fitting, the correlation coefficient of the

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calculated data exceeds 0.99, and the sensitivity is 3.79 µA/Hz. This phenomenon can be explained by Eq (1), I is the short circuit current, Q is the amount of transfer charge and t is the time of one cycle of contact between the object and PO-STENG. Therefore, when the amount of charge accumulated on the PDMS/OMMT-CTAM is constant, the shorter the cycle time is, that is, the higher the working frequency is, the higher output current of PO-STENG is. (1)

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I = Q/t

Experiment with temperature as a single variable was done to explore the temperature sensing performance of the triboelectric sensor. The working temperature was controlled by a heating device,

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and the surface temperature of the PO-STENG was measured in real time by an infrared temperature detector. Figure 3a illustrates its temperature sensing performance, when the working temperature increased from 19.4 ℃ to 34.9 ℃ , which is the temperature range of human daily life, the output

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current of the PO-STENG increased from 7.2 µA to 16.4 µA. This shows that it is a good performance temperature sensor with a sensitivity of 0.59 µA/℃. PO-STENG, as an intelligent sensor, also has the bionic function of recognizing the different materials which it contacts with. A test which used a linear motor to drive different types of materials with the same area to contact with PO-STENG was done to test its output current. Six typical materials, including polyethylene terephthalate (PET), sponge, terylene, polymethyl methacrylate (PMMA), copper (Cu) and aluminum (Al), were chosen to test. Figure 3b exhibits that six different materials produce six different current signals. PET generated the minimum current while Cu generated the maximum 8

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detectable and sensitive to Cu.

Figure 3. . Applications of the PO-STENG as a triboelectric sensor. (a) Short circuit current of the PO-STENG under different working temperature. (b) Short circuit current of the PO-STENG

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contacted with different materials. (c) Short circuit current of the PO-STENG contacted with soft and hard materials. (d) Shape of current peak of the PO-STENG contacted with soft and hard materials.

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Insets show the working mechanism.

PO-STENG can recognize not only the type of object but also the hardness of the object. Figure 3c shows the current generated by Cu with different hardness to contact with PO-STENG. The soft Cu contacted with the device generated a larger current while the hard one produced a smaller current. The data and working mechanism diagram in Figure 3d can explain this phenomenon. When PO-STENG contacts hard Cu, the output current is low and the half peak width is small. On the contrary, when it comes into contact with soft Cu, the output current is higher and the half peak width is larger. The explanation for this phenomenon can be found in the working mechanism diagram. For soft objects, applying a small force can lead to obvious deformation of the 9

ACCEPTED MANUSCRIPT contact object, and friction is constantly generated in the process of deformation. At the same time, charge will be generated in the process of friction, the output current will increase with the accumulation of charge. On the contrary, for a hard object, applying a small force will not cause a large deformation of the object. Therefore, most of the current comes from the moment of contact, so,

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the output current is small. PO-STENG, as a kind of triboelectric sensor can recognize not only different kinds of materials but also the hardness of materials. This makes it has a broad application

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prospect in the field of bionic skin of intelligent robot.

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. Applications of the PO-STENG as a location detection system. (a) Working Figure 4. mechanism of location sensing. (b) Voltage distribution of the PO-STENG when contacted with different locations. (c) The current ratio of the PO-STENG with different locations. (d) Comparison

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between the testing point and the location result. In the intelligent sensing system of an intelligent robot, it is not only necessary to know the physical properties of the contact object, but also to know the exact contact position. Therefore, PO-STENG was designed as a location detection system. Four induced electrodes were placed on the four sides of the friction layer of PO-STENG (Figure 1a). The working mechanism of location detection is briefly described in Figure 4a. When the object came into contact with the friction layer (PDMS/OMMT-CTAB), charge exchange would occur with the surface of the object. As a result, excessive charge accumulation was generated on the PDMS/OMMT-CTAB. This led to a change in 10

ACCEPTED MANUSCRIPT the potential near the contact point, which induced a corresponding potential at the induction electrode. The voltage distribution at different contact points can be obtained by finite element analysis (Figure 4b). Through the corresponding data processing of this output electrical signals, the current distribution changes on the electrode induced at different contact points are obtained, and

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then the corresponding contact point position information can be obtained too. According to the simulation results, when the position of the contact point is changed, the current on each electrode will change. Specifically, the electrode near the contact point of PDMS/OMMT-CTAB is negatively charged due to the contact. The closer the electrode is to the contact point, the greater the influence

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of these negative charges will be. Using this property, the middle area of the electrode was divided into 25 small areas, and the current generated on the induced electrode after each point contact was

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measured. Figure 4c shows the relationship between the ratio of the current on the relative position electrode and the position was established. In order to verify the location detection function and explore the effect of ZnO on the accuracy of the location detection function, two samples, one was the PO-STENG with ZnO and the other one was the PO-STENG without ZnO, were tested. For the PO-STENG without ZnO, point (1.5, 3.0) was selected for testing. As we can see in the figure 4d

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when the testing point was (1.5, 3.0), the location result was (1.42, 2.25), and the deviation of the positioning system without ZnO is about 7.5 mm. Similarly, Point (2.5, 4.5) was selected for testing the accuracy of the PO-STENG with ZnO, Figure 4d shows that when the testing point was (2.5, 4.5),

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the point obtained by analyzing the current value was (2.38,4.35). This indicates that the deviation of the positioning system with ZnO is only 2 mm, and it has good accuracy. It is obvious that ZnO enhances the positioning accuracy of the PO-STENG. This is because the ZnO nanowires have a

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piezoelectric effect when the device subjected to external forces, the charges in the device are increased, thus enhancing the current sensitivity of each Ag electrode in the device. In order to further study the output characteristics of PO-STENG, the power of the device was measured by adding different load resistors to the external circuit. Eight load resistors were selected as external resistors to measure the current and voltage output performance of PO-STENG. Figure 5a shows the voltage and current of the device under different load resistors. On this basis, the power under different load resistors was calculated (P = UI) (Figure 5b). When the load resistance is 10.8 MΩ, the external load instantaneous power of PO-STENG reaches the peak of 1387 µW (0.087 11

ACCEPTED MANUSCRIPT mW/cm2). It’s worth mentioning that the endurance quality of this device is beyond compare. Under the condition of 2 Hz contact frequency and keep working for 10 min (1200 cycles), it can still maintain stable performance (Figure 5c). This ensures that when PO-STENG is used as a flexible electronic skin, it can effectively convert the mechanical energy in the environment into electrical

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energy. As illustrates in Figure 5d, when given an external force, PO-STENG can easily light up 34 LEDs. In addition, when a simple circuit is designed and a capacitor is connected in parallel to the PO-STENG (Figure 5e), it can power some small electronic products, such as watches (Figure 5f)

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and light shoes (Figure S3).

Figure 5. . Applications of the PO-STENG as a power source. (a) Outputs of the PO-STENG under different load resistances. (b) Power of the PO-STENG under different load resistances. (c) Stability of the PO-STENG working for 1200 cycles. (d) LEDs lighted by the PO-STENG. (e) Circuit diagram of the system that the electronics charged by PO-STENG with the capacitor. (f) Electronic watch powered by the PO-STENG with the capacitor. 12

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3. Conclusion In summary, a kind of inorganic modified composite film (PDMS/OMMT-CTAB) was used to

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construct a highly stretchable TENG-based triboelectric sensor (PO-STENG). The maximum output voltage of PO-STENG (4 cm×4 cm) is 160 V and the maximum output current is 12.4 µA. When the load resistance is 10.8 MΩ, the external load instantaneous power of PO-STENG reaches the peak of 1387 µW (0.087 mW/cm2). The PO-STENG can recognize not only the type of the object contacted

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with it but also the hardness of the object. The sensitivity of the pressure sensing component is up to 0.04 µA/KPa and the linear pressure detection range is from 16 KPa to 64 KPa with a correlation

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coefficient of 0.993. And the detection range of the temperature sensing is from 19.4 ℃ to 34.9 ℃ with a sensitivity of 0.59 µA/℃. In addition, a location detection based on PO-STENG was constructed, which can accurately track the position of the object with a deviation of only 2 mm. It has the functions as a power source and multifunctional sensor (Figure 6) which can be applied to

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many fields such as artificial intelligence, robotics, touch screen, and other electronic devices.

Figure 6. . Functions of the PO-STENG as a power source and multifunctional sensor.

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ACCEPTED MANUSCRIPT 4. Experimental Section 4.1. Fabrication of the composite structure film OMMT and hexane were mixed in the ratio of 1:9 (w/w). Then the dispersed suspension liquid was obtained by stirring for 20 hours. Elastomer and the cross-linker (Sylgard 184, Dow Corning)

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were prepared in the ratio of 10:1 (w/w). Then pour the mixed solution into PDMS and ultrasound for 30 minutes after stir for 15 minutes at high speed. The mixture was placed on the mold by the spin-coating method at 500 rpm for 120 s and was cured at room temperature for 24 h and the mold was removed carefully. Finally, the based on PDMS composite structure film was obtained.

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4.2. Fabrication of ZnO micro/nanowires

ZnO micro/nanowires were prepared by vapor−liquid−solid growth process. High-purity ZnO

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powders and carbon powders were mixed uniformly in the ratio of 1:1 (w/w). The cleaned silicon wafer which coated with 3 nm gold was placed on corundum crucible which was put in mixed powder. Then put the corundum crucible in the center of the furnace tube. The temperature of the furnace tube was raised from 200 ℃ to 980 ℃ at 30 ℃/min and the reaction system was filled with oxygen at the flow rate of 20 sccm. Then the system was naturally cooled after kept 980 ℃ for 1 h.

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Finally, the ZnO micro/nanowires were obtained. 4.3. Fabrication of Silver Nanowire Electrodes

The solution with the 200 nm diameter and 25 µm length of commercial Ag nanowire

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(XFNANO, China) was coated and formed four electrodes on the composite structure film surface after several times dilution. Then the Ag nanowires were coated with a copper electrode, and the copper wire was fixed to the electrode and elicited by silver gel. The ZnO nanowire was transferred

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to the middle position of the electrode and formed into a regular network structure. Then a layer of composite structure film was adhered onto the surface and cured. 4.4. Characterization and Measurements The surface morphology of the elastomer, the Ag nanowires, and the ZnO nanowires were characterized by Nova NanoSEM 450. For the measurement of output electric signals of the PO-STENG, a homemade motor system was used to supply the external mechanical force. The electrical outputs of the PO-STENG were measured, acquisited and analyzed by an electrometer (Keithley 6514, TEKTRONIX, INC) with computer measurement software written in LabVIEW. 14

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

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Acknowledgments We thank the financial support from the Beijing Municipal Science & Technology Commission, China (No.Z171100002017017), National key R and D project from Minister of Science and Technology, China (2016YFA0202702), the National Natural Science Foundation of China (NSFC

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No. 51873020, 21575009, 51432005 and Y4YR011001), the "Thousands Talents" program for pioneer researcher and his innovation team, China, the National Postdoctoral Program for Innovative

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Talents (No. BX20180081), and China Postdoctoral Science Foundation (No. 2019M650604).

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ACCEPTED MANUSCRIPT

Yu Cheng received his B.S. degree from Central South University in 2017. He is currently a master degree candidate at the Beijing Institute of Nanoenergy and Nanosystems, Chinese

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Academic of Sciences. His research interests include flexible electronic skin, micro/nano-energy

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devices and self-powered systems.

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Dan Wu received her master degree candidate of the Research Center for Bioengineering and Sensing Technology at the University of Science and Technology Beijing. Her

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research interests include electrochemical sensors and self-powered micro-nano-systems.

Saifei Hao received her B.S. degree from Nanjing Agricultural University in 2017.

She is currently a master degree candidate at the Beijing Institute of Nanoenergy and Nanosystems, Chinese Academic of Sciences. Her current research mainly focuses on material design and synthesis, energy harvesting and fabrication of devices.

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Yang Jie received his Ph.D degree from University of Science and Technology

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Beijing in 2018. He is currently a postdoctoral fellow at the Beijing Institute of Nanoenergy and Nanosystems, Chinese Academy of Sciences. His research interests include nanogenerators and

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self-powered micro-/nano-systems.

Xia Cao is currently a distinguished professor at University of Science and Technology Beijing, and a professor at Beijing Institute of Nanoenergy and Nanosystems, Chinese Her main

research

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Academy of Sciences.

interests

focus

on

the energy materials,

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nanoelectroanalytical chemistry, self-powered nano-biosensors and piezoelectric sensors.

Ning Wang is currently a Professor at University of Science and Technology Beijing.

His research interest is the application of energy conversion interface to smart devices and to understand fundamental mechanisms underlying experimentally observed phenomena with specific focus on biomimetic tactile sensors.

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Zhong Lin Wang received his Ph.D. from Arizona State University in physics. He

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now is the Hightower Chair in Materials Science and Engineering, Regents’ Professor, Engineering Distinguished Professor and Director, Center for Nanostructure Characterization, at Georgia Tech. Dr. Wang has made original and innovative contributions to the synthesis, discovery, characterization and understanding of fundamental physical properties of oxide nanobelts and nanowires, as well as

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applications of nanowires in energy sciences, electronics, optoelectronics and biological science. His discovery and breakthroughs in developing nanogenerators established the principle and

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technological road map for harvesting mechanical energy from environment and biological systems for powering personal electronics. His research on selfpowered nanosystems has inspired the worldwide effort in academia and industry for studying energy for micro-nano-systems, which is now a distinct disciplinary in energy research and future sensor networks. He coined and pioneered the field of piezotronics and piezo-phototronics by introducing piezoelectric potential gated charge

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transport process in fabricating new electronic and optoelectronic devices. Details can be found at:

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http://www.nanoscience.gatech.edu.

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ACCEPTED MANUSCRIPT Highlights

A TENG-based triboelectric sensor has been designed for electronic skin by a

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convenient inorganic modification method.

The triboelectric sensor is highly stretchable which can up to 580%.

The triboelectric sensor integrates dynamic force sensing, temperature sensing

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and hardness sensing.

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A location detection system based on the triboelectric sensor has been designed

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whose location detection sensitivity is 2 mm.