Flexible Organic Tribotronic Transistor for Pressure ... - ACS Publications

Nov 3, 2017 - School of Material Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, United States. •S Supporting Info...
0 downloads 16 Views 1MB Size
Subscriber access provided by READING UNIV

Article

Flexible Organic Tribotronic Transistor for Pressure and Magnetic Sensing Junqing Zhao, Hang Guo, Yao Kun Pang, Fengben Xi, Zhi Wei Yang, Guoxu Liu, Tong Guo, Guifang Dong, Chi Zhang, and Zhong Lin Wang ACS Nano, Just Accepted Manuscript • DOI: 10.1021/acsnano.7b06480 • Publication Date (Web): 03 Nov 2017 Downloaded from http://pubs.acs.org on November 5, 2017

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

ACS Nano is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 22

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Nano

Flexible Organic Tribotronic Transistor for Pressure and Magnetic Sensing Junqing Zhao†,§,⊥,▲, Hang Guo‡,▲, Yao Kun Pang†,§,⊥, Fengben Xi †,§,⊥, Zhi Wei Yang †,§, ⊥

, Guoxu Liu†,§,⊥, Tong Guo †,§,⊥, Guifang Dong ‡, *, Chi Zhang †,§,⊥,*, Zhong Lin Wang†,§,

⊥,ǁ,*

† Beijing Institute of Nanoenergy and Nanosystems, Chinese Academy of Sciences, Beijing 100083, China ‡ Key Laboratory of Organic Optoelectronics and Molecular Engineering of Ministry of Education, Chemistry Department, Tsinghua University, Beijing 100084, PR China § CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology (NCNST), Beijing, 100190, China; ⊥ University of Chinese Academy of Sciences, Beijing 100049, China ǁ School of Material Science and Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA

ACS Paragon Plus Environment

1

ACS Nano

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 2 of 22

ABSTRACT Flexible electronics has attracted enormous interests in wearable electronics and human-machine interfacing. Here, a flexible organic tribotronic transistor (FOTT) without top gate electrode has been demonstrated. The FOTT is fabricated on a flexible polyethylene terephthalate (PET) film using the p-type pentacene and polymethyl methacrylate/Cytop (PMMA/Cytop) composites as conductive channel and dielectric layer, respectively. The charge carriers can be modulated by the contact electrification between the dielectric layer and a mobile triboelectric layer. Based on the fabricated FOTT, pressure and magnetic sensors have been developed, respectively, which exhibit great sensitivity, fast response time and excellent stability. The FOTT in this simple structure shows bright potentials of tribotronics in human-machine interaction, electronic skins, wearable electronics, intelligent sensing, and so on.

KEYWORDS: organic tribotronic transistor, triboelectric nanogenerator, tribotronics, pressure sensor, magnetic sensor

ACS Paragon Plus Environment

2

Page 3 of 22

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Nano

ToC figure

Over the past decades, flexible electronics has attracted enormous interests in wearable devices, smart skins and human-machine interfacing.1-4 As one of the key technologies for flexible electronics, organic thin film transistor (OTFT), which possesses combined advantages of low cost, low temperature and large area, has been widely studied.5-8 However, most OTFT-based sensors are usually modulated by electrical signals, which are in shortage of active and direct interaction with the environment. Therefore, seeking for an active sensing mechanism that can bridge the gap between the ambient and sensors and develop direct human-machine interaction is highly desirable. Recently, triboelectric nanogenerator (TENG), which is based on the coupling of triboelectrification and electrostatic induction, has three major application fields of the micro/nano energy,9-13 self-powered systems,14-21 and blue energy. 22-24 Furthermore, tribotronics has been proposed by coupling with triboelectricity and semiconductor, which can be used for information sensing,25, 26 and active control.27 So far, plenty of tribotronic devices which have been demonstrated including electro-mechanical coupled logic circuits,28 contact-gated lightemitting LED,29 organic touch memory,30 adjustable phototransistor,31, 32 smart tactile switch,33

ACS Paragon Plus Environment

3

ACS Nano

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 4 of 22

electronic skins,34 tactile sensing array,35 flexible transparent transistor,36 tribotronic tuning diode37 and force pad.38, 39 All of these applications demonstrate the huge potentials of the tribotronics in flexible and active interaction electronics, offering a prospective strategy to design smart sensors with advantages of low cost, simple mechanism, and excellent flexibility. Here, we developed a flexible organic tribotronic transistor (FOTT) without the top gate electrode. With a pentacene conductive channel and a polymethyl methacrylate/Cytop (PMMA/Cytop) composites dielectric layer fabricated on a flexible polyethylene terephthalate (PET) substrate, the FOTT can be greatly modulated by contact electrification between the dielectric layer and a mobile triboelectric layer. Furthermore, the FOTT displays great sensing ability in pressure and magnetic detection with great sensitivity, fast response time and excellent stability. The FOTT without top gate electrode as a simple tribotronic device in this work shows great potential in human-machine interaction, electronic skins, wearable electronics, intelligent sensing, and so on.

RESULTS AND DISCUSSION Structure of the FOTT. As shown in Figure 1(a), the FOTT is fabricated on a flexible PET film substrate, consisting of a mobile triboelectric layer and an OTFT without top gate electrode. First, a 300 nm Ta2O5 film is sputtered on the PET surface. Then, the conductive channel, 45 nm thick pentacene film, is deposited by thermal evaporation. Subsequently, two parallel Au drain/source electrodes are deposited on the pentacene film through shadow masks and the thickness is controlled to about 45 nm. Thereafter, PMMA and Cytop are spin-coated as the dielectric layer, respectively. Figure 1(b) shows the optical graph of the as-fabricated FOTT in

ACS Paragon Plus Environment

4

Page 5 of 22

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Nano

top view. As shown in the graph, the conductive channel of the FOTT is 60 µm in length and 1000 µm in width, respectively. Figure 1(c) presents the equivalent circuit of the FOTT. The electrical potential difference, acting as the gate voltage, is generated from the movement of TENG by the external pressure, which can modulate the IDS.

Working mechanism and performance of the FOTT. The FOTT, in a simple structure without top gate electrode, presents a totally different working principle from the conventional OTFT configuration. The enhancement mode of the device is shown in Figure 2. As demonstrated in Figure 2(a), the copper (Cu) film is purposely chosen as the mobile triboelectric layer. The drain electrode of the FOTT is connected with a voltage source while the source electrode is grounded. When the Cu film fully contacts with the PMMA/Cytop dielectric, positive charges are induced on the surface of the Cu film while negative charges are formed on PMMA/Cytop surface according to their triboelectric series. At this moment, there is no electrical potential difference and no charge carrier concentration changes in the pentacene film because the negative and positive charges on the two surfaces are fully balanced. As a result, no obvious change can be observed in the IDS. Once the Cu film gradually separates from the PMMA/Cytop surface, the negative charges on the PMMA/Cytop film surface will induce an inner charge polarization, leading to establishment of an inner electric field across the pentacene conductive channel and the PMMA/Cytop surface. This process results in the holes accumulating to the interface of the pentacene and the PMMA/Cytop layers to achieve an enhancement zone in the pentacene conductive channel and an increase in the IDS is observed. When the Cu film continues the separation movement, the inner electric field gradually increases and IDS is enhanced. After that, the Cu film begins to approach the PMMA/Cytop surface, and the

ACS Paragon Plus Environment

5

ACS Nano

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 6 of 22

enhancement zone will be depressed owing to the accumulative hole carriers being diffused away from the interface of the pentacene and the PMMA/Cytop layers. Accordingly, the IDS will decrease. When the Cu film returns to its originally full contact state, the IDS recovers to the original value. Illustrated in Figure S1 are the theoretically calculated results (performed by the software Comsol Multi-physics) of the potential difference generated from contact and separation cycle between the mobile triboelectric layer and the PMMA/Cytop surface, indicating that this triboelectric potential varies with the separation distance of the mobile triboelectric layer. Apart from the working principle mentioned above, the relationship between the IDS and the separation distance of the Cu film is systematically studied. The separation distance of the Cu film can be accurately controlled and measured using a linear motor. Figure 2(b) plots the output characteristic of the FOTT device without external gate voltage in the enhancement mode. As shown in the graph, the IDS rises up as the separation distance increasing within a VDS of 0~-10 V. The IDS change as a function of separation distance at a constant VDS of -10 V is also studied as shown in Figure 2(c). The inset image presents the transfer characteristics of the FOTT device. When the separation distance of Cu film varies from 0 to 700 µm, the IDS increases from -2.84 µA to -3.25 µA, which is in good accordance with the working principle elucidated in Figure 2(a). The on/off value, defended as the ratio of the IDS generated at the two separation distance (0 and 700 µm, respectively) can be reached at 1.14. Besides in the enhancement, the depletion mode of the FOTT device is also analyzed in Figure 3. Different from the structure in the enhancement mode, the Fluorinated ethylene propylene (FEP) film acts as the mobile triboelectric layer. Figure 3(a) demonstrates the working mechanism of the FOTT in the depletion mode. Negative charges are induced on the surface of

ACS Paragon Plus Environment

6

Page 7 of 22

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Nano

FEP film while positive charges are generated on PMMA/Cytop surface when the two surfaces are in contact. Likewise, the channel carrier concentration is still not influenced at this moment. As the FEP film slowly moves away from the PMMA/Cytop surface, an inner electric field is generated, causing the holes being repelled away from the interface of the pentacene and the PMMA/Cytop, and thus creating a depletion zone in the pentacene conductive channel. Similarly, the depletion zone will be enlarged and the IDS will continually drops until a maximum separation distance of FEP film is reached. When the FEP film is approaching the surface of PMMA/Cytop to the full contact state, the hole carriers move back to the interface of the pentacene and the PMMA/Cytop layers. In this stage, the inner charge polarization is depressed, which decreases the inner electric field and the depletion zone and yet restores holes carrier concentration in the interface and the IDS. Figure 3(b) shows the output characteristic of the FOTT at different separation distance of the FEP film without external gate voltage. Clearly shown in the graph is the increasing trend of the IDS as the separation distance. The relationship between the IDS (VDS maintains -10 V) and the separation distance of the FEP film is provided in Figure 3(c), and the inset image is the corresponding transfer characteristics of the FOTT device. A separation distance increased from 0 to 600 µm results in the IDS changing from -2.91 µA to -1.69 µA, where an on/off ratio as high as 1.72 can be realized in the depletion mode.

Application of the FOTT for pressure sensing. On the basis of the above experimental results, the IDS can be modulated by contact electrification between a mobile triboelectric layer and the PMMA/Cytop dielectric layer. Here, if the mobile triboelectric layer moves and contacts

ACS Paragon Plus Environment

7

ACS Nano

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 8 of 22

with the dielectric layer by applying an external pressure, the IDS can be used for sensing the external pressure. With this principle, we have developed a pressure sensor based on the FOTT. The structure and sensing process of the pressure sensor are displayed in Figure 4(a). As shown in the figure, the FEP film, working as mobile triboelectric layer, is fixed on the FOTT through two polyimide (PI) tapes. The FEP film is separated from the PMMA/Cytop surface initially and can contact with it by the external pressure. Due to the contact electrification, negative charges are generated on the surface of FEP film while positive charges are generated on the PMMA/Cytop surface. At the initial state, because of the inner charge polarization by the positive charges on the PMMA/Cytop surface, the hole carriers move away from the interface of the pentacene and the PMMA/Cytop layers, and a depletion zone is created in the pentacene conductive channel. When the pressure is applied, the FEP film is deformed to approach the PMMA/Cytop surface, which depresses the inner charge polarization and the depletion zone, and yet restores holes carrier concentration in the interface to increase the IDS. When the pressure gradually increases until the FEP film and the PMMA/Cytop completely contact with each other, the IDS value increases to the maximum level. Therefore, the IDS change can be determined by the applied pressure. Figure 4(b) reveals the IDS change of the FOTT during press-release processes. Consistent with the analysis above is the IDS increase/decrease when the FEP film is pressed /released. In order to visualize the IDS change under the modulation of the external force, the sensor is utilized as the switch through an amplifier circuit to an LED light for illumination. The LED is turned on when the sensor is in pressed state while turned off in released state. Dynamic demonstrations can be found in Video S1. An interesting phenomenon is that the FEP film thickness will affect the performance of the sensor. The IDS shown in Figure 4(c) reduces obviously with the increased FEP film thickness

ACS Paragon Plus Environment

8

Page 9 of 22

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Nano

under the same external pressure. It may be ascribed to the reduced distortion of the FEP film in large thickness, which has diminished the modulation effect on the IDS. In this work, 100 µm thick FEP film has been selected to fabricate a pressure sensor and the pressure sensing properties are illustrated in Figure 4(d). The sensor exhibits good sensing performance with a high linear correlation coefficient about 0.980 within the pressure range of 20~1000 Pa. The sensitivity of this pressure sensor is defined as S = (∆I/I0)/ ∆P, where ∆I represents the relative change in current, I0 is the current of the sensor without pressure loading, and ∆P is the relative change in the applied pressure. By taking advantage of the distinct response of the device as a function of the applied pressure, a maximum sensitivity of 21% Pa-1 is calculated. The temporal response of the pressure sensor during a quick press-release process shows a fast response time of 110 ms and a recovery time of 120 ms, as depicted in Figure S2. Moreover, the persistence and repeatability experiment of the pressure sensor is depicted in Figure S3. As a consequence, the FOTT as a pressure sensor has shown promising prospects in wearable electronics and intelligent sensing.

Application of the FOTT for magnetic sensing. Besides as the contact pressure sensor, another intriguing application of the FOTT is the non-contact magnetic sensing. By further adding magnetic composites into the triboelectric layer, a magnetic sensor is developed. Figure 5(a) presents the structure and sensing process of the magnetic sensor. To begin with, the Fe3O4/PDMS magnetic composites, spin-coated on the top surface of the FEP film, are fixed on the FOTT. Figure 5(b) illustrates the Atomic Force Microscope (AFM) image of the PDMS/Fe3O4 composites. Figure S4 reveals the detail fabrication process. The Fe3O4/PDMS magnetic composites will deform and get close to the PMMA/Cytop dielectric layer by magnetic

ACS Paragon Plus Environment

9

ACS Nano

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 10 of 22

force when a magnet touches the bottom surface, which is equal to narrow the depletion zone in the pentacene conductive channel. This will increase the IDS. However, when the magnet is taken away, the Fe3O4/PDMS magnetic composites will recover to the initial state and the depletion zone will increase, leading to the decrement of the IDS. A sensing device with excellent flexibility is shown in Figure 5(c). Moreover, the IDS changes of the sensor with a 200 mT magnetic field on and off are shown in Figure 5(d) (the device operates under a constant VDS of -10 V). When no magnetic field is loaded, the IDS maintains unchanged and no obvious current modulation is observed. Once a magnetic field is introduced, the IDS increases obviously, which indicates a good potential in magnetic sensing. A demonstration about IDS change by switching an LED light through an amplifier circuit is shown in Video S2. Notably, the IDS is related to Fe3O4/PDMS magnetic composites thickness, with corresponding experiment results shown in Figure 5(e). A rising trend of the IDS before the magnetic film thickness reaches about 250 µm is observed, and after that, it begins to decrease. This can be explained as the multi-effects of magnetic particles content and the thickness. Commonly, the magnetic particles content increases with the thickness increasing, as well as the magnetic force. However, the increasing thickness also hinders the distortion process. Accordingly, 250 µm is selected as the optimal thickness for PDMS/Fe3O4 magnetic composites. With these magnetic composites, a flexible FOTT magnetic sensor has been developed with characteristics as shown in Figure 5(f). From the figure, the current is dramatically risen from 2.44 µA to -2.83 µA as the magnetic field increases within the range of 1~150 mT. Furthermore, the linear correlation coefficient between the magnetic field and the IDS is 0.983. The sensitivity of our magnetic sensor is defined as S = (∆I/I0)/ ∆B, where ∆I denotes the relative change in current, I0 is the current of the sensor without magnetic loading, and ∆B is the relative change in

ACS Paragon Plus Environment

10

Page 11 of 22

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Nano

the applied magnetic field. By calculation, we obtained a maximum sensitivity of 16% mT-1. In order to further assess the sensing performance of the FOTT-based magnetic sensor, we investigate the magnetic field-dependent current change response, which exhibits a fast response and recovery time (seen in Figure S5). Compared with previous magnetic sensors, 40, 41 which exhibits the response time of 130 ms to 2.85 s, the FOTT-based magnetic sensor exhibits a faster response time of 120 ms. Furthermore, previous reported magnetic sensors exhibit sensitivity of 0.093% to 2.5% mT−1 in a magnetic field of several hundreds of mT, 42-44 which demonstrated that the sensitivity of our device is obviously higher than that of previous reports. Moreover, the measurements for about ten thousand cycles are carried out to validate the stability and repeatability of the device, as shown in Figure 5(g). Even after ten thousands of times test cycles, the changes in the IDS amount to less than 5%, showing its little hysteresis and excellent reproducibility. One important cause of the excellent stability is that there is no traditional top gate electrode in the FOTT, which can avoid the device performance degradation caused by electrode damage in the device bending process as well as simplify the preparation process. All these results may promise a bright future of this magnetic sensor in intelligent sensing and control.

CONCLUSIONS In summary, a flexible organic tribotronic transistor without top gate electrode has been developed by using the p-type pentacene and PMMA/Cytop composites as the conductive channel and the dielectric layer, respectively. By making the mobile triboelectric layer contact with and separate from the PMMA/Cytop dielectric surface, the IDS will increase in the

ACS Paragon Plus Environment

11

ACS Nano

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 12 of 22

enhancement mode while decrease dramatically in the depletion mode. This FOTT can be further used as a pressure sensor that exhibits a great sensitivity as high as 21% Pa-1 and fast response time of 110 ms in the pressure range of 20~1000 Pa. Moreover, this FOTT can also be used for magnetic sensing with sensitivity of 16% mT-1, fast response time of 120 ms and excellent stability for more than 10000 cycles when the sensor operates at 1~150 mT. The FOTT in the simple structure, with pressure-magnetic-sensing capability in this work, shows bright potentials of tribotronics in human-machine interaction, smart skins, wearable devices, intelligent sensing, and so on. METHODS Fabrication process of the FOTT. First, a 300 nm Ta2O5 film is sputtered on the surface a flexible PET substrate which is cleaned by ultrasonic in deionized water for 4 times. Then, a 45 nm pentacene (Sigma-Aldrich, >99%, used as received) film is thermally evaporated at a deposition rate of 0.01~0.02 nm s−1 under a 1×10−4 Pa vacuum. After that, 45 nm Au drain/source electrodes are deposited on two sides of the pentacene film through shadow masks. Finally, PMMA (Sigma-Aldrich) and Cytop are spin-coated (3000 rpm s-1, 1500 rpm s-1) as the dielectric layer, respectively. The final step is by annealing the device in a glove box at 100 ℃ for 1 h. Fabrication of the pressure sensor. The pressure sensor is proposed by attaching two polyimide (PI) tapes with 300 µm on the FOTT to fix the fluorinated ethylene propylene (FEP) as the mobile triboelectric layer. Fabrication of the magnetic sensor. The Fe3O4 nanoparticles (Aladdin, particle size: 300-500 nm) are added into poly (dimethylsiloxane) (PDMS) (Dow Corning 184) and then

ACS Paragon Plus Environment

12

Page 13 of 22

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Nano

stirring. Then, Fe3O4/PDMS composites are spin-coated (2000 rpm s-1) onto the FEP film and drying at 60 ℃. The sample is peeled off after 1 h. Finally, the Fe3O4/PDMS composites are fixed on the FOTT by two PI tapes. Thereby, the magnetic sensor is well-prepared. Electrical measurements of the FOTT. The I-V curves in Figure 2 and Figure 3 are measured using a Keysight B1500A semiconductor parameter analyzer. The other experiment data are measured by a DS 345 synthesized function generator in conjunction with a SR570 lownoise current amplifier (Stanford Research System). Different magnetic intensities are measured by a magnetometer through changing the distance between the magnet and the bottom surface of the PET substrate. ASSOCIATED CONTENT Supporting Information This Supporting Information is available free of charge via the Internet at http://pubs.acs.org. Figures S1−S5 (PDF) Tribotronic transistor for pressure sensing (Video S1) (AVI) Tribotronic transistor for magnetic sensing (Video S2) (AVI) AUTHOR INFORMATION Corresponding Authors *

E-mail: [email protected] (C. Zhang),

*

E-mail: [email protected] (G. Dong),

ACS Paragon Plus Environment

13

ACS Nano

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

*

Page 14 of 22

E-mail: [email protected] (Z. L. Wang).

Author Contributions ▲

These authors contributed equally to this work.

Conflict of Interest: The authors declare no competing financial interest.

ACKNOWLEDGEMENTS The authors thank the support of National Key Research and Development Program of China (2016YFA0202704), National Natural Science Foundation of China (No. 51475099), Beijing Nova Program (No. Z171100001117054), the Youth Innovation Promotion Association, CAS (No. 2014033), the "thousands talents" program for the pioneer researcher and his innovation team, China. The authors also thank Xianpeng Fu and Tianzhao Bu for their contributions in the whole experiment. REFERENCES (1) Rogers, J. A.; Someya, T.; Huang, Y. Materials and Mechanics for Stretchable Electronics. Science 2010, 327, 1603–1607. (2) Kim, D.-H.; Lu, N.; Ma, R.; Kim, Y.-S.; Kim, R.-H.; Wang, S.; Wu, J.; Won, S. M.; Tao, H.; Islam, A.; Yu, K. J.; Kim, T.-I.; Chowdhury, R.; Ying, M.; Xu, L.; Li, M.; Chung, H.-J.; Keum, H.; McCormick, M.; Liu, P.; Zhang, Y.-W.; Omenetto, F. G.; Huang, Y.; Coleman, T.; Rogers, J. A. Epidermal Electronics. Science 2011, 333, 838–843. (3) Chortos, A.; Bao, Z. Skin-Inspired Electronic Devices. Mater. Today 2014, 17, 321–331. (4) Hammock, M. L.; Chortos, A.; Tee, B. C. K.; Tok, J. B. H.; Bao, Z. 25th Anniversary Article: The Evolution of Electronic Skin (E-Skin): A Brief History, Design Considerations, and Recent Progress. Adv. Mater. 2013, 25, 5997–6038. (5) Sun, Q.; Kim, D. H.; Park, S. S.; Lee, N. Y.; Zhang, Y.; Lee, J. H.; Cho, K.; Cho, J. H. Transparent, Low-Power Pressure Sensor Matrix Based on Coplanar-Gate Graphene Transistors. Adv. Mater. 2014, 26, 4735–4740.

ACS Paragon Plus Environment

14

Page 15 of 22

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Nano

(6) Sun, Q.; Seung, W.; Kim, B. J.; Seo, S.; Kim, S. W.; Cho, J. H. Active Matrix Electronic Skin Strain Sensor Based on Piezopotential-Powered Graphene Transistors. Adv. Mater. 2015, 27, 3411–3417. (7) Knopfmacher, O.; Hammock, M. L.; Appleton, A. L.; Schwartz, G.; Mei, J.; Lei, T.; Pei, J.; Bao, Z. Highly Stable Organic Polymer Field-Effect Transistor Sensor for Selective Detection in the Marine Environment. Nat. Commun. 2014, 5, 2954. (8) Chou, H.-H.; Nguyen, A.; Chortos, A.; To, J. W. F.; Lu, C.; Mei, J.; Kurosawa, T.; Bae, W.G.; Tok, J. B.-H.; Bao, Z. A Chameleon-Inspired Stretchable Electronic Skin with Interactive Colour Changing Controlled by Tactile Sensing. Nat. Commun. 2015, 6, 8011. (9) Zhang, C.; Zhou, T.; Tang, W.; Han, C.; Zhang, L.; Wang, Z. L. Rotating-Disk-Based DirectCurrent Triboelectric Nanogenerator. Adv. Energy Mater. 2014, 4, 1301798. (10) Zhang, C.; Tang, W.; Han, C.; Fan, F.; Wang, Z. L. Theoretical Comparison, Equivalent Transformation, and Conjunction Operations of Electromagnetic Induction Generator and Triboelectric Nanogenerator for Harvesting Mechanical Energy. Adv. Mater. 2014, 26, 3580– 3591. (11) Zhou, T.; Zhang, C.; Bao Han, C.; Ru Fan, F.; Tang, W.; Lin Wang, Z. Woven Structured Triboelectric Nanogenerator for Wearable Devices. ACS Appl. Mater. Interfaces 2014, 6, 14695– 14701. (12) Zhou, T.; Zhang, L.; Xue, F.; Tang, W.; Zhang, C.; Wang, Z. L. Multilayered Electret Films Based Triboelectric Nanogenerator. Nano Res. 2016, 9, 1442–1451. (13) Huang, L. B.; Bai, G.; Wong, M. C.; Yang, Z.; Xu, W.; Hao, J. Magnetic-Assisted Noncontact Triboelectric Nanogenerator Converting Mechanical Energy into Electricity and Light Emissions. Adv. Mater. 2016, 28, 2744–2751. (14) Bao Han, C.; Zhang, C.; Li, X. H.; Zhang, L.; Zhou, T.; Hu, W.; Lin Wang, Z. Self-Powered Velocity and Trajectory Tracking Sensor Array Made of Planar Triboelectric Nanogenerator Pixels. Nano Energy 2014, 9, 325–333. (15) Tang, W.; Zhou, T.; Zhang, C.; Ru Fan, F.; Bao Han, C.; Lin Wang, Z. A PowerTransformed-and-Managed Triboelectric Nanogenerator and Its Applications in a Self-Powered Wireless Sensing Node. Nanotechnology 2014, 25, 225402. (16) Zhang, L.; Xue, F.; Du, W.; Han, C.; Zhang, C.; Wang, Z. Transparent Paper-Based Triboelectric Nanogenerator as a Page Mark and Anti-Theft Sensor. Nano Res. 2014, 7, 1215– 1223. (17) Pang, Y. K.; Li, X. H.; Chen, M. X.; Han, C. B.; Zhang, C.; Wang, Z. L. Triboelectric Nanogenerators as a Self-Powered 3D Acceleration Sensor. ACS Appl. Mater. Interfaces 2015, 7, 19076–19082. (18) Lee, K. Y.; Yoon, H. J.; Jiang, T.; Wen, X.; Seung, W.; Kim, S. W.; Wang, Z. L. Fully Packaged Self-Powered Triboelectric Pressure Sensor Using Hemispheres-Array. Adv. Energy Mater. 2016, 6, 1502566. (19) Luo, J.; Tang, W.; Fan, F. R.; Liu, C.; Pang, Y.; Cao, G.; Wang, Z. L. Transparent and Flexible Self-Charging Power Film and Its Application in a Sliding Unlock System in Touchpad Technology. ACS Nano 2016, 10, 8078–8086. (20) Wang, X.; Zhang, H.; Dong, L.; Han, X.; Du, W.; Zhai, J.; Pan, C.; Wang, Z. L. SelfPowered High-Resolution and Pressure-Sensitive Triboelectric Sensor Matrix for Real-Time Tactile Mapping. Adv. Mater. 2016, 28, 2896–2903.

ACS Paragon Plus Environment

15

ACS Nano

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 16 of 22

(21) Sun, J. G.; Yang, T. N.; Kuo, I. S.; Wu, J. M.; Wang, C. Y.; Chen, L. J. A Leaf-Molded Transparent Triboelectric Nanogenerator for Smart Multifunctional Applications. Nano Energy 2017, 32, 180–186. (22) Zhang, L. M.; Han, C. B.; Jiang, T.; Zhou, T.; Li, X. H.; Zhang, C.; Wang, Z. L. Multilayer Wavy-Structured Robust Triboelectric Nanogenerator for Harvesting Water Wave Energy. Nano Energy 2016, 22, 87–94. (23) Wang, Z. L.; Jiang, T.; Xu, L. Toward the Blue Energy Dream by Triboelectric Nanogenerator Networks. Nano Energy 2017, 39, 9–23. (24) Huang, L. biao; Xu, W.; Bai, G.; Wong, M. C.; Yang, Z.; Hao, J. Wind Energy and Blue Energy Harvesting Based on Magnetic-Assisted Noncontact Triboelectric Nanogenerator. Nano Energy 2016, 30, 36–42. (25) Zhang, C.; Tang, W.; Zhang, L.; Han, C.; Wang, Z. L.; Academy, C.; Science, M.; States, U. Contact Electrification Field-Efect Transisitor. 2014, 8, 8702–8709. (26) Zhang, C.; Wang, Z. L. Tribotronics—A New Field by Coupling Triboelectricity and Semiconductor. Nano Today 2016, 11, 521–536. (27) Xi, F.; Pang, Y.; Li, W.; Jiang, T.; Zhang, L.; Guo, T.; Liu, G.; Zhang, C.; Wang, Z. L. Universal Power Management Strategy for Triboelectric Nanogenerator. Nano Energy 2017, 37, 168–176. (28) Zhang, C.; Zhang, L. M.; Tang, W.; Han, C. B.; Wang, Z. L. Tribotronic Logic Circuits and Basic Operations. Adv. Mater. 2015, 27, 3533–3540. (29) Zhang, C.; Li, J.; Han, C. B.; Zhang, L. M.; Chen, X. Y.; Wang, L. D.; Dong, G. F.; Wang, Z. L. Organic Tribotronic Transistor for Contact-Electrification-Gated Light-Emitting Diode. Adv. Funct. Mater. 2015, 25, 5625–5632. (30) Li, J.; Zhang, C.; Duan, L.; Zhang, L. M.; Wang, L. D.; Dong, G. F.; Wang, Z. L. Flexible Organic Tribotronic Transistor Memory for a Visible and Wearable Touch Monitoring System. Adv. Mater. 2016, 28, 106–110. (31) Zhang, C.; Zhang, Z. H.; Yang, X.; Zhou, T.; Han, C. B.; Wang, Z. L. Tribotronic Phototransistor for Enhanced Photodetection and Hybrid Energy Harvesting. Adv. Funct. Mater. 2016, 26, 2554–2560. (32) Pang, Y.; Xue, F.; Wang, L.; Chen, J.; Luo, J.; Jiang, T.; Zhang, C.; Wang, Z. L. Tribotronic Enhanced Photoresponsivity of a MoS2 Phototransistor. Adv. Sci. 2015, 3, 1500419. (33) Xue, F.; Chen, L.; Wang, L.; Pang, Y.; Chen, J.; Zhang, C.; Wang, Z. L. MoS2 Tribotronic Transistor for Smart Tactile Switch. Adv. Funct. Mater. 2016, 26, 2104–2109. (34) Khan, U.; Kim, T. H.; Ryu, H.; Seung, W.; Kim, S. W. Graphene Tribotronics for Electronic Skin and Touch Screen Applications. Adv. Mater. 2017, 29, 1603544. (35) Yang, Z. W.; Pang, Y.; Zhang, L.; Lu, C.; Chen, J.; Zhou, T.; Zhang, C.; Wang, Z. L. Tribotronic Transistor Array as an Active Tactile Sensing System. ACS Nano 2016, 10, 10912– 10920. (36) Pang, Y.; Li, J.; Zhou, T.; Yang, Z.; Luo, J.; Zhang, L.; Dong, G.; Zhang, C.; Wang, Z. L. Flexible Transparent Tribotronic Transistor for Active Modulation of Conventional Electronics. Nano Energy 2017, 31, 533–540. (37) Zhou, T.; Yang, Z. W.; Pang, Y.; Xu, L.; Zhang, C.; Wang, Z. L. Tribotronic Tuning Diode for Active Analog Signal Modulation. ACS Nano 2017, 11, 882–888. (38) Wu, J. M.; Lin, Y. H.; Yang, B. Z. Force-Pad Made from Contact-Electrification Poly(ethylene oxide)/InSb Field-Effect Transistor. Nano Energy 2016, 22, 468–474.

ACS Paragon Plus Environment

16

Page 17 of 22

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Nano

(39) Yang, B. Z.; Lin, Y. S.; Wu, J. M. Flexible Contact-Electrification Field-Effect Transistor Made from the P3HT:PCBM Conductive Polymer Thin Film. Appl. Mater. Today 2017, 9, 96– 103. (40) Wong, M. C.; Chen, L.; Tsang, M. K.; Zhang, Y.; Hao, J. Magnetic-Induced Luminescence from Flexible Composite Laminates by Coupling Magnetic Field to Piezophotonic Effect. Adv. Mater. 2015, 27, 4488–4495. (41) Yang, Y.; Lin, L.; Zhang, Y.; Jing, Q.; Hou, T. C.; Wang, Z. L. Self-Powered Magnetic Sensor Based on a Triboelectric Nanogenerator. ACS Nano 2012, 6, 10378–10383. (42) Karnaushenko, D.; Makarov, D.; Stöber, M.; Karnaushenko, D. D.; Baunack, S.; Schmidt, O. G. High-Performance Magnetic Sensorics for Printable and Flexible Electronics. Adv. Mater. 2015, 27, 880–885. (43) Melzer, M.; Lin, G.; Makarov, D.; Schmidt, O. G. Stretchable Spin Valves on Elastomer Membranes by Predetermined Periodic Fracture and Random Wrinkling. Adv. Mater. 2012, 24, 6468–6472. (44) Melzer, M.; Kaltenbrunner, M.; Makarov, D.; Karnaushenko, D.; Karnaushenko, D.; Sekitani, T.; Someya, T.; Schmidt, O. G. Imperceptible Magnetoelectronics. Nat. Commun. 2015, 6, 6080.

ACS Paragon Plus Environment

17

ACS Nano

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 18 of 22

Figure 1. Schematic illustration of the flexible organic tribotronic transistor (FOTT). (a) Structure of the FOTT without top-gate electrode. (b) Optical graph of the as-fabricated FOTT. (c) Equivalent circuit of the FOTT.

Figure 2. Characteristics of the FOTT in enhancement mode. (a) Schematic working principle of the FOTT in the enhancement mode using a Cu film as the mobile triboelectric layer. (b) Output characteristics of the FOTT with different separation distances. (c) IDS output characteristics at a constant drain voltage (VDS) of -10 V with different separation distances (the separation distance is defined as d). The inset is the IDS-d transfer characteristics of the FOTT in enhancement mode.

ACS Paragon Plus Environment

18

Page 19 of 22

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Nano

Figure 3. Characteristics of the FOTT in depletion mode. (a) Schematic working principle of the FOTT in the depletion mode using a FEP film as the mobile triboelectric layer. (b) Output characteristics with varying separation distances. (c) IDS output characteristics at a constant VDS of -10 V with different separation distances. The inset is the IDS-d transfer characteristics of the FOTT in depletion mode.

ACS Paragon Plus Environment

19

ACS Nano

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 20 of 22

Figure 4. Structures and performances of the FOTT for pressure sensing. (a) Schematic illustration of the device structure and the sensing process. (b) IDS changes of the sensor during periodical press-release processes. (c) IDS changes as a function of the FEP film thickness (the normal pressure remains 20 Pa during the whole process). (d) IDS output characteristics at a FEP film thickness of 100 µm with different input pressures. The inset is the fitted curves.

ACS Paragon Plus Environment

20

Page 21 of 22

ACS Nano

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 ACS Paragon Plus Environment

21

ACS Nano

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 22 of 22

Figure 5. Structures and performances of the FOTT for magnetic sensing. (a) Schematic illustration of the device structure and the sensing process. (b) Atomic Force Microscope (AFM) image of the PDMS/Fe3O4 composites. (c) Photograph of a flexible sensing device demonstrating its excellent flexibility. (d) IDS changes of the sensor with a magnetic field on and off. (e) IDS changes corresponding to a magnetic field of 200 mT with different PDMS/Fe3O4 composites thicknesses. (f) IDS output characteristics with different magnetic field. A fitted curve is displayed in the inset. (g) Stability test of the sensor. VDS maintains at -10 V during the whole experiment. A little hysteresis and good repeatbility are attained even after about 10000-cycle tests.

ACS Paragon Plus Environment

22