Waterproof Electronic-Bandage with Tunable Sensitivity for

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Waterproof electronic-bandage with tunable sensitivity for wearable strain sensors Jun-Young Jeon, and Tae-Jun Ha ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.5b12201 • Publication Date (Web): 11 Jan 2016 Downloaded from http://pubs.acs.org on January 19, 2016

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ACS Applied Materials & Interfaces

Waterproof electronic-bandage with tunable sensitivity for wearable strain sensors Jun-Young Jeon, Tae-Jun Ha* Department of Electronic Materials Engineering, Kwangwoon University, Seoul 139-701, Republic of Korea *Corresponding author: [email protected]

Abstract Keyword: E-bandage, carbon nanotube, conducting nanoparticle, PDMS, human-interactive sensor

We demonstrate high-performance wearable electronic-bandage (E-bandage) based on carbon nanotube (CNT)/silver nanoparticle (AgNP) composites covered with a flexible media of fluoropolymer-coated polydimethylsiloxane (PDMS) films. The E-bandage can be used for motion-related sensors by directly attaching them to human skin, which achieves a fast and accurate electric response with a high sensitivity according to bending and stretching movements that induce changes in the conductivity. This advance in the E-bandage is realized as a result of the sensitivity that can be achieved by controlling the concentration of AgNPs in CNTs and by modifying the device architecture. The fluoropolymer encapsulation with hydrophobic surface characteristics allows for the E-bandage to operate in water and protects them from physical and chemical contact with the daily-life conditions of the human skin. The reliability and scalability of the E-bandage as well as the compatibility with conventional micro-fabrication

allow

new

possibilities

to

integrate

flexible

human-interactive

nanoelectronics into mobile health-care monitoring systems combined with internet of things (IoTs) .

ACS Paragon Plus Environment


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Introduction Flexible electronics that rely on the flexible properties of conventional and/or advanced materials have been extensively explored in order to overcome the limitations inherent to conventional substrates, including space.1-5 A promising approach to obtain functional flexible interfaces is to apply wearable motion-related sensors on humans and animals.6-8 Such sensors can be realized by employing active materials with the corresponding device architecture to perceive the change in the electrical characteristics according to the bending and pressure.9-13 In contrast to other electronic applications, humaninterface sensors must be 1) directly attached to the human skin to allow convenient mounting/dismounting, 2) guarantee safe and reliable electrical operation, 3) integrate an encapsulation scheme that protects the sensor from undesirable environmental effects, and 4) exclude risking the user’s health. The key to satisfy all of these conditions is to develop a optimized device configuration combined with novel materials which exhibit excellent electrical and mechanical characteristics, and thus to enable the wide-spread adoption of flexible on-skin human-interface sensors. Carbon nanotube (CNT) based nano-electronics have been of great scientific and technological interest due to their low-cost solution-process with large-area fabrication, chemical and mechanical stability and compatibility with flexible substrates including polydimethylsiloxane (PDMS) and polyimide (PI).14-17 CNT networks with functional properties can be obtained by producing composites with electrically conductive nanoparticles, such as silver nanopaticle (AgNP).18-20 We observed that conductive nanoparticle films that are not being embedded into CNT network exhibit irreversible cracks or even breakage beyond a certain strain value, which leads to the immediate sensor failure and is not suitable for the resistive type of strain sensors. Instead, we blended AgNPs and CNT paste to form CNT/AgNP composites, as Takei et al., reported previously19 and


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observed very robust and sensitive device performance. Furthermore, the conductivity of such CNT/AgNP composites increased by a factor of 1000 relative to that of CNT networks without AgNPs. There have been reports to demonstrate highly stretchable sensors that detect the strain up to 50% by using silver nanowires and over 900% by using CNT fibers, which can be achieved through the proposed structures and materials.13,21 In this work, we have focused on high performance wearable CNT-based strain sensors with tunable sensitivity. To date, a number of studies have presented CNT-based sensors that make use of intramolecular interactions with chemicals.22-23 However, very few of these have focused on the electrical engineering aspect of producing CNT-based composites that have a tunable conductivity for use with wearable sensor electronics that are intended to be waterproof with electrical isolation. In this paper, we demonstrate the use of waterproof electronic-bandage (E-bandage) based on CNT/AgNP composites embedded in a fluoropolymer-coated PDMS sandwich structure for wearable strain sensors. Theses sensors satisfy all of the above key requirements for human-interactive electronics to detect movement of joints and muscles where we utilize CNT/AgNP composites with a high sensitivity in the electrical resistance. We also demonstrate the applications of the E-bandage for the mobile health monitoring system directly attached to the human skin of wrist, face and leg. With optimized device configuration, the E-bandage exhibited the robust stability in water and 0.5 mol/L sodium chloride solutions in order to ensure stable operation in a daily-life environment. Our results contribute to the field of CNT-based nano-electronics by advancing knowledge of promising sensor applications in bio-electronics. We noted that papers which contain similar methods and materials have been published elsewhere. However, to the best of our knowledge, it is the first paper to demonstrate the stable operation of CNT-based human-interactive electronics directly attached to the human skin against the environmental contacts.



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Experiments The device architecture of the E-bandage for wearable strain sensors is based on a sandwich structure consisting of a 40 µm-thick CNT/AgNP composite as the sensing component embedded into a 300 µm-thick PDMS as a flexible substrate, as shown in Figure 1 (a). Both sides of the CNT/AgNP composite are covered by the fluoropolymer-coated PDMS films which possess hydrophobic surface and dielectric characteristics.24-25 For this reason, the E-bandage is properly protected from physical and chemical contact, and at the same time, an electric current does not flow through human skin during the sensor operation due to the non-wettability and electrical isolation. To avoid a decrease in the sensitivity of the CNT/AgNP composite as a sensor, we employed an asymmetric thicknesses for the PDMS films which are 300 µm-thick for a bottom substrate film and 500 µm-thick for a top encapsulation film because the bending leads to tension in one film and compression in the other film at the same time. If the thickness of the top film is same as that of the bottom film, the neutral point is placed at the center where the CNT/AgNP composite film is located.19 The fabrication of the E-bandage starts with PDMS (Ellsworth; Dow Corning Sylgard 184 Silicone Encapsulant 0.5kg Kit Clear) as a flexible substrate. PMDS was de-gassed in a vacuum for 1 hour to remove air bubbles, deposited via spin-coating onto a silicon handing wafer that was previously treated with trichloro(1H,1H,2H,2H-perfluorooctyl)silane (Sigma Aldrich Co.) and then cured at 80 °C for 1 hour in air. In order to enhance the adhesion between a PDMS film and CNT/AgNP composites, the PDMS film was pre-treated with UV ozone at the wavelength of 253 nm and the power density of 28 mW/cm2 for 25 minutes. Asreceived AgNP ink (Paru Co. Ltd.; PG-007, 82 wt% in Ethylene glycol, the size of 20 ~100 nm, the resistance of 2~3 ohm) and CNT paste (SWeNT Inc.; ~ 50wt % CNT in a polymer binder) were blended to form CNT/AgNP composites in the ratio of weight percentage.19 The concentration of AgNP in the CNT paste is controlled to tune the conductivity because the


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charge transport through the AgNPs becomes dominant rather than that through the CNTs. The CNT/AgNP composite was subsequently patterned into lines with a width of 0.3 cm and a length of 1.6 cm and was then annealed at 70 °C for 15 minutes in air to remove residual solvents from the polymer binder in the CNT paste. Finally, the samples were encapsulated with PDMS films surface-coated by amorphous fluoropolymer, Teflon-AF(Poly[4,5-difluoro2,2-bis(trifluoromethyl)-1,3-dioxole-co-tetrafluoroethylene]; Dupont co. 400S2-100-1: 1% solution) which possesses strong hydrophobic surface (see Figure S1 in the supporting information).26-27 The E-bandage was connected with the wire and the resistance meter to measure the resistance value. The electrical contact was carefully secured to avoid affecting the change in resistance of E-bandage. Figure 1 (b) shows the optical image of the E-bandage for wearable strain sensor directly attached to human skin where the sensor was mounted on the joint of a finger. The proposed device configuration enables to easily mount the CNT/AgNP composite film on any area of the human skin without producing major discomfort and health risk. In addition, the device is very robust and reliable on the human skin until disposal. We also fabricated an E-bandage with a micro-scale feature size that possesses a high sensitivity by using a SU-8 mold. The dimension of the E-bandage were defined by a patterned micro-channel of 200 µm (see Figure S2 in the supporting information). The E-bandage for wearable strain sensors can be compatible with conventional micro-fabrication processes to ensure scalability and uniformity.

Results and Discussion Figure 2 (a) shows scanning electron microscope (SEM) images of as-deposited and stretched (20%) CNT/AgNP composites on a PDMS film. Whereas densely packed AgNPs in the CNT network were observed on an as-deposited sample, a smaller numbers of sparse AgNPs including some cracks were observed when the strain was applied. The tunneling



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distance between the nanoparticles that create the current path increases, which results in a decrease in conductance. The increase in electric resistance from 2.3 Ω to 2 kΩ is in good qualitative agreement with the change in morphology in the CNT/AgNP composite on PDMS film as measured by SEM, as shown in Figure 2 (a). As the applied strain increased up to 30% from the 10%, the crack became conspicuous with bigger size. (See Figure S3 in the supporting information). It must be noted that such electric functionality was not achieved in the composites which we employed other conducting nanoparticles such as gold and graphene into. When we utilize such electrical characteristics in CNT/AgNP composites as a sensing component, the sensitivity is the key to realize high performance strain sensors. Figure 2 (b) shows the sensitivity (defined as the difference in resistance between the initial and final divided by the initial resistance: ∆R/Ro) as a function of bending strain (below 4%) on the E-bandage with different concentration of AgNP in the CNT paste. Within the bending strain of 3.2%, the sensitivity of the E-bandage reached up to 2.5. It must be noted that the sensitivity of E-bandage was changed very dramatically beyond the certain level of the applied strain. (See Figure S4 in the supporting information). A similar observation was reported in Ref. [13]. An increase in the concentration of AgNPs from 10 wt% to 50 wt% in the CNT paste enhanced the sensitivity of the sensor, which means that we are able to control the sensitivity of the strain sensor by changing the concentration ratio of the AgNPs in the CNT paste. Figure 2 (c) shows the morphology of CNT/AgNP composite films with different concentrations on PDMS substrates, which was obtained by atomic force microscopy (AFM) measurements. A more dense distribution of the AgNPs in 50 wt% CNT paste with larger domains was observed, which can lead to the improvement in tunneling for charge transport.28-29 Furthermore, the film roughness increases from 115 to 223 nm by a factor of two as the concentration of AgNPs increases from 10 wt% to 50 wt% in the CNT paste. When the deformation was applied on the E-bandage, the strain profile in the local position of


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CNT/AgNP composite film can be affected by the film roughness thereby influencing the sensitivity for strain sensors. Figure 2 (d) shows the 3 dimensional morphology of CNT/AgNP (50 wt%) composite films with different substrates of PDMS and PI. The film roughness of it on PDMS substrate is 172 nm where that on PI substrate is 79 nm. It is in good agreement with that the change in conductance of CNT/AgNP composite film on a PI substrate is much suppressed compared to that on a PDMS substrate when the bending strain was applied.

Next, we investigated the effect of device configuration on the electrical sensitivity of the E-bandage by changing the dimension of width and length, as shown in figure 3 (a) and (b). The sensitivity of E-bandage increased when a length increased at the width of 0.3 cm and a width decreased at the length of 1.6 cm. The results support that the strain profile can be affected by the device configuration where the electrical sensitivity of E-bandage can be tuned with the optimized device design. In order to characterize the electrical properties of CNT/AgNP composite films as a strain sensor in terms of the real-time response and the repeatability, we also conducted the time-domain strain measurement on the E-bandage.30-32 The strain was loaded on the E-bandage at 1 second. After the holding time for 4 second, the E-bandage was released. Figure 3 (c) shows that the E-bandage exhibited good repeatability during loading (10%) and unloading (0%) cycles with a simultaneous time response for 1 hour. The E-bandage can be employed as a wearable motion sensor on human skin by recharacterizing the electrical characteristics according to the joint bending angle. As shown in figure 3 (d), the measurement circuit using a simple switching method was used to characterize the E-bandage as a human-interactive sensor. The input voltage from the power supply was applied to the E-bandage connected to the simple circuit consisting of the resistance and the capacitance which were modulated by the change in resistance of the E-



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bandage at the attached position. When the strain was applied (the finger was bent), the resistance in the E-bandage increased and the output voltage was connected to the ground. When the strain was released, the resistance in the E-bandage decreased and the output voltage was connected to the input voltage. By using DAQ board with MATLAB programmed, the output voltage was in real-time displayed on a screen. A strain profile for the sensitivity as a function of the bending angle provides additional information to consider the design margin of sensitivity with the actual degree of strain. The region with the highest amount of strain (up to a strain of 15%) was confined within a strain profile of 5 mm from the bending point. Since the overall resistance of the E-bandage consists of the sum of that of local regions, the sensitivity can be dominated by the increase in resistance of the E-bandage at the highest strained region. For this reason, we can realize a highly sensitive wearable strain sensor with the E-bandage based on CNT/AgNP composite films, which can successfully operate even at the strain of below 4% on the finger joint directly, as shown in figure 3 (e). Such a functionality for the E-bandage as a motion sensor has been demonstrated by using a simple electric circuit that consists of a light-emitting diode (LED), a power supply (1–2V) and electric wires. It must be noted that an electric current does not flow through human skin because the E-bandage is fully encapsulated with dielectric films in both sides. The LED light turns from “on” to “off” according to the increase in electrical resistance of the 50 wt% CNT/AgNP composite when the E-bandage has been bent. Figure 3 (f) shows the successful operation of the E-bandage for wearable motion sensors on finger joints. Each sensor operates independently but simultaneously, which provides detailed information of finger movement. We further observed a continuous variation in the electrical characteristics of the E-bandage under gradual changes in the joint bending angle.

Various sensor applications can be realized by making use of the electrical


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functionality of the E-bandage to interact with human. For example, we can control the spin speed of a fan connected to the E-bandage by changing the resistance caused by the bending movement, which is visibly demonstrated by the position of paper placed directly over the fan (see Figure S5 in the supporting information). To successfully operate the E-bandage for human-interactive sensors, it is critical for the electrical characteristic of the CNT/AgNP composites in each position to not be affected by others. We investigated the feasibility of using the E-bandage attached to the human finger-wrist-elbow to realize multi-functional sensors. Figure 4 (a) shows that multi-sensing operation was successfully demonstrated by tracking the electrical characteristics of E-bandage in each position of finger, wrist and elbow independently. Based on multi-functional operations, we extended the use in the E-bandage to detect the unexpected movement of muscles caused by nystagmus and convulsion on the face. Figure 4 (b) show that the E-bandage successfully responded to the sensitive movements on the muscle of human face in the weak strain regiem. By using the E-bandage integrated into the internet of things, the mobile health-care monitoring system and the electronic security system can be realized to process the data of balance maintenance (including calorie consumption) and voice recognition. Figure 4 (c) and 4 (d) show that the fast and accurate response of the E-bandage as a wearable human-interactive sensor corresponding to the movement of the knee joint and the larynx was observed when the muscles were activated during the walking and the speaking. It must be noted that highly sensitive detection (the applied strain of below 4%) in the E-bandage to sense the clenching/unclenching can be achieved by employing our proposed combination of optimized material synthesis and engineered device configuration. (see Figure S4 in the supporting information)

Wearable sensors attached to human skin may be negatively affected by physical and/or chemical contact with daily-life conditions (water, sweat, dirt, etc.) during the



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operation.33 For this reason, it is essential to secure the stability of the E-bandage by preventing from physical and/or chemical interaction with contamination from outside environment. Figure 5 (a) shows that the E-bandage in water and in 0.5 mol/L sodium chloride solutions (0.03~0.08 mol/L correspond to sweat on human skin) operate without signs of degradation for 100 hours. A fully encapsulated E-bandage with hydrophobic fluoropolymer can be a very promising candidate for human-interface sensors to aim at reallife conditions wet with sweat, water and other liquids. Figure 5 (b) demonstrates the waterproof characteristics of the E-bandage by successfully operating the bending sensor in water. The E-bandage includes electric connections with a power supply and an LED light fully immersed in water. During the entire cycle of movement in a finger, the LED light responded to each state according to the changes in resistance of the E-bandage.

Conclusion In summary, we have successfully demonstrated the waterproof E-bandage consisting of CNT-based composites sandwiched with fluoropolymer-coated PDMS films for wearable strain sensors with tunable sensitivity. Comprehensive applications of the E-bandage on different positions of the human skin, such as the finger, wrist, elbow, face, and leg to detect the sensitive movement (the applied strain of below 4%) in joint and muscle have been investigated. Our results support the E-bandage exhibits good performance with selective sensitivity as well as excellent stability against physical and chemical contact for wearable human-interactive sensors. Such advances can be realized for a wide range of applications by controlling the concentration of AgNPs in the CNT paste and by designing the appropriate device architecture. Our work suggests good reliability and scalability of the E-bandage platform and thus opens up new routes to integrate nanoelectronics into flexible health monitoring IoTs at the system level.


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Supporting information The Supporting information is available free of charge on the ACS Publications website at http://pubs.acs.org The contact angle of fluoropolymer measured by the optical microscope, the E-bandage with a micro-scale feature size by using a SU-8 mold, the change in morphology in the CNT/AgNP composite on PDMS film under different strains as measured by SEM, the sensitivity as a function of bending strain on the E-bandage with different concentration of AgNP in the CNT paste, the application of the electrical functionality in the E-bandage to interact with human visibly demonstrated by the position of paper placed directly over the fan, and the sensor application for highly sensitive detection in the E-bandage to sense the clenching/unclenching

AUTHOR INFORMATION Corresponding Author [email protected]

Acknowledgement The work was supported by the Research Grant of Kwangwoon University and by the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT and Future Planning.(2014R1A2A1A12067505) The author thanks Prof. Cheolsoo Park, Prof. Wi Hyoung Lee, and Prof. Ali Javey for supporting this work.

Reference 1. Nathan, A.; Ahnood, A.; Cole, M. T.; Sungsik, L.; Suzuki, Y.; Hiralal, P.; Bonaccorso, F.;



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

Hasan, T.; Garcia-Gancedo, L.; Dyadyusha, A.; Haque, S.; Andrew, p.; Hofmann, S.; Moultrie, J.; Chu, D.; Flewitt, A.; Ferrari, A.; Kelly, M.; Robertson, J.; Amaratunga, G.; Milne, W. Flexible Electronics: The Next Ubiquitous Platform. Proc. IEEE 2012, 100, 1486– 1517. 2. Han, J.-W.; Kim, B.; Li, J.; Meyyappan, M. Carbon Nanotube Based Humidity Sensor on Cellulose Paper. J. Phys. Chem. C 2012, 116, 22094–22097. 3. Zardetto, V.; Brown, T.M.; Reale, A.; Di Carlo, A. Substrates for Flexible Electronics: a Practical Investigation on the Electrical, Film Flexibility, Optical, Temperature, and Solvent Resistance Proper. J. Polym. Sci. PART B 2011, 49, 638–648. 4. Bauer, S. Flexible Electronics: Sophisticated Skin. Nat. Mater. 2013, 12, 871–872. 5. Siegel, A. C; Phillips, S. T.; Dickey, M. D.; Lu, N.; Suo, Z.; Whitesides, G. M. Foldable Printed Circuit Boards on Paper Substrates. Adv. Funct. Mater. 2010, 20, 28-35. 6. Benight, J.; Wang, C.; Tok, J. B.; Bao, Z. Stretchable and Self-Healing Polymers and Devices for Electronic Skin. Pro. Polym. Phys. 2013, 38, 1961-1977. 7. Segev-Bar, M.; Haick, H. Flexible Sensors Based on Nanoparticles. ACS Nano 2013, 7, 8366−8378. 8. Jeong, J. W.; Yeo, W. H.; Akhtar, A.; Norton, J. J.; Kwack, Y. J.; Li, S.; Jung, S.Y.; Su, Y.; Lee, W.; Xia, J.; Cheng, H.; Huang, Y.; Choi, W.S.; Bretl,Y.; Rogers, J. A. Materials and Optimized Designs for Human-Machine Interfaces via Epidermal Electronics. Adv. Mater. 2013, 25, 6839-6846. 9. Pang, C.; Lee, G.-Y.; Kim, T. -I.; Kim, S. M.; Kim, H. N.; Ahn, S.-H.; Suh, K.-Y. A Flexible and Highly Sensitive Strain-Gauge Sensor Using Reversible Interlocking of Nanofibers. Nat. Mater. 2012, 11, 795-801. 10. Bae, S.-H.; Lee, Y.; Sharma, B. K.; Lee, H.-J.; Kim, J.-H.; Ahn, J.-H. Graphene-Based Transparent Strain Sensor. Carbon 2013, 51, 236-242. 11. Rogers, J. A.; Someya, T.; Huang, Y. Materials and Mechanics for Stretchable Electronics. Science 2010, 327, 1603-1607. 12. Park, M.; Im, J.; Shin, M.; Min, Y.; Park, J.; Cho, H.; Park, S.; Shim, M. -B.; Jeon, S.; Chung, D. -Y.; Bae, J.; Park, J.; Jeong, U.; Kim, K. Highly Stretchable Electric Circuits from a Composite Material of Silver Nanoparticles and Elastomeric Fibres, Nat. Nanotechnol. 2012, 7, 803-809. 13. Ryu, S.; Lee, P.; Chou, J. B.; Xu, R.; Zhao, R.; Hart, A. J.; Kim, S. -G. Extremely Elastic Wearable Carbon Nanotube Fiber Strain Sensor for Monitoring of Human Motion. ACS Nano, 2015, 9, 5929-5936. 14. Hu, B.; Chenb, W.; Zhoua, J. High Performance Flexible Sensor Based on Inorganic Nanomaterials. Sens. Actuators B: Chemical 2013, 176, 522–533. 15. Wang, Y.; Yang, R.; Shi, Z.; Zhang, L.; Shi, D.; Wang, E.; Zhang, G. Super-Elastic Graphene Ripples for Flexible Strain Sensors. ACS Nano 2011, 5, 3645-3650. 16. Chandra, B.; Park, H.; Maarouf, A.; Martyna, J.; Tulevski, S. Carbon Nanotube Thin Film Transistors on Flexible Substrates. Appl. Phys. Lett. 2011, 99, 072110. 17. Cai, L.; Song, L.; Luan, P.; Zhang, Q.; Zhang, N.; Gao, Q.; Zhao, D.; Zhang, X.; Tu, M.; Yang, F.; Zhou, W.; Fan, Q.; Luo, j.; Zhou, W.; Ajayan, P.; Xie, S. Superstretchable, Transparent Carbon Nanotube-Based Capacitive Strain Sensors for Human Motion Detection. Sci. Rep. 2013, 3, 3048. 18. Chen, K. -Y.; Oh, Y.; Rho, J.; Ahn, J. -H.; Kim, Y. -J.; Choi, H. R.; Baik, S. Highly Conductive, Printable and Stretchable Composite Films of Carbon Nanotubes and Silver. Nat. Nanotechnol. 2010, 5, 853-857. 19. Takei, K.; Yu, Z.; Zheng, M.; Ota, H.; Takahashi, T.; Javey, A. Highly Sensitive Electronic Whiskers Based on Patterned Carbon Nanotube and Silver Nanoparticle


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Composite Films. Proc. Natl. Acad. Sci. 2014, 111, 1703–1707. 20. Harada, S.; Honda, W.; Arie, T.; Akita, S.; Takei, K. Fully Printed, Highly Sensitive Multifunctional Artificial Electronic Whisker Arrays Integrated with Strain and Temperature Sensors. ACS Nano 2014, 8, 3921–3927. 21. Yao, S.; Zhu, Y. Wearable Multifunctional Sensors Using Printed Stretchable Conductors Made of Silver Nanowires. Nanoscale 2014, 6, 2345-2352. 22. Wang, J. Carbon-Nanotube Based Electrochemical Biosensors: A Review. Electroanalysis. 2005, 17, 7-14. 23. Mao, S.; Lu, V; Chen, J. Nanocarbon-Based Gas Sensors: Progress and Challenges. J. Mater. Chem. A. 2014, 2, 5573–5579. 24. Ha, T. -J.; Lee, J.; Chowdhury, Sk. F.; Akinwande, D.; Rossky, P. J.; Dodabalapur, A. Transformation of the Electrical Characteristics of Graphene Field-Effect Transistors with Fluoropolymer. ACS Appl. Mater. Interfaces. 2013, 5, 16-20. 25. Ha, T.-J.; Kiriya, D.; Chen, K.; Javey, A. Highly Stable Hysteresis-Free Carbon Nanotube Thin-Film Transistors by Fluorocarbon Polymer Encapsulation. ACS Appl. Mater. Interfaces. 2014, 6, 8441–8446. 26. Wu, C.-W.; Gong, G.-C. Fabrication of PDMS-Based Nitrite Sensors Using Teflon AF Coating Microchannels. IEEE Sens. J. 2008, 8, 465-469. 27. Scharnberg, M; Zaporojtchenko, V.; Adelung, R.; Faupel, F.; Pannemann, C.; Diekmann, T.; Hilleringmann U. Tuning the Threshold Voltage of Organic Field-Effect Transistors by an Electret Encapsulating layer. Appl. Phys. Lett. 2007, 90, 013501. 28. Herrmann, J.; Müller, K.-H.; Reda, T.; Baxter,; Raguse, B.; de Groot, G.J.J.B.; Chai, R.; Roberts, M.; Wieczorek, L. Nanoparticle Films as Sensitive Strain Gauges. Appl. Phys. Lett. 2007, 91, 183105. 29. Hu, N.; Karube, Y.; Yan, C.; Masuda, Z.; Fukunaga, H. Tunneling Effect in a Polymer/Carbon Nanotube Nanocomposite Strain Sensor. Acta Materialia. 2008, 56. 2929– 2936. 30. Kang, I.; Schulz, M. J.; Kim, J. H.; Shanov, V.; Shi, D. A Carbon Nanotube Strain Sensor for Structural Health Monitoring. Smart Mater. Struct. 2006, 15, 737-748. 31. Lipomi, D. J.; Vosgueritchian,M.; Tee, B. C-K.; Hellstrom, S. L.; Lee, J. A.; Fox, C. H.; Bao, Z. Skin-Like Pressure and Strain Sensors Based on Transparent Elastic Films of Carbon Nanotubes. Nat. Nanotechnol. 2011, 6, 788-792. 32. Yamada, T.; Hayamizu, Y.; Yamamoto, Y.; Yomogida, Y.; Izadi-Najafabadi, A.; Futaba, D. N.; Hata, K. A Stretchable Carbon Nanotube Strain Sensor for Human-Motion Detection. Nat. Nanotechnol. 2011, 6, 296-301. 33. Kim, R. -H.; Kim, D. -H.; Xiao, J.; Kim, B. H.; Park, S. -I.; Panilaitis, B.; Ghaffari, R.; Yao, J.; Li, M.; Liu, Z.; Malyarchuk, V.; Kim, D. G.; Le, A. -P.; Nuzzo, R. G.; Kaplan, D. L.; Omenetto, F. G.; Huang, Y.; Kang, Z.; Rogers, J. A. Waterproof AlInGaP Optoelectronics on Stretchable Substrates with Applications in Biomedicine and Robotics. Nat. Mater. 2010, 9, 929-937.



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FIGURE CAPTIONS Figure 1 (a) The device architecture of the E-bandage for wearable strain sensors by employing a sandwich structure and (b) the optical image of the E-bandage directly attached to human skin Figure 2 (a) The SEM images of as-deposited and stretched (20%) CNT/AgNP composites on a PDMS film, (b) the sensitivity as a function of bending strain on the E-bandage with different concentration of AgNP in the CNT paste, (c) the morphology of CNT/AgNP composite films with different concentrations on PDMS substrates obtained by AFM measurements, and (d) the 3 dimensional morphology of CNT/AgNP (50 wt%) composite films with different substrates of PDMS and PI Figure 3 The sensitivity as a function of bending strain with different dimension of (a) length and (b) width, (c) the change in resistance of E-bandage during real-time strain (10%) and release (0%) cycles with a simultaneous time response for 1 hour, (d) the illustration of the measurement circuit using a simple switching method to characterize the E-bandage as a human-interactive sensor, and the operation of the E-bandage for wearable motion sensors on (e) one finger individually controlled and (f) four fingers independently controlled. Figure 4 The multi-sensing operation of the E-bandage attached to the (a) human fingerwrist-elbow and (b) human face and the response of the E-bandage corresponding to the movement of (c) the knee joint and (d) the larynx Figure 5 (a) the stability of E-bandage in water and in 0.5 mol/L sodium chloride solutions for 100 hours and (b) the waterproof characteristics of the E-bandage by successfully operating the bending sensor in water


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a)

b)

5mm

figure 1 ACS Paragon Plus Environment


a)

3.0

b)

Bending

No bending

CNT: AgNPs = 5:5 CNT: AgNPs = 7:3 CNT: AgNPs = 9:1

2.5 2.0 R/R0

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

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1.5 1.0 0.5

200 nm

c)

9:1

200 nm

7:3

0.0 5:5

d)

0

1

2 Strain (%)

3

4

um 0.8 0

um 0.4 -0.4

5

5

5

5 1um

1um

1um


0

PDMS

0

PI

b) 3.0

length of 1.6 cm length of 1.2 cm length of 0.8 cm

2.5

2.5 2.0 R/R0

2.0 1.5 1.0

width of 0.3 cm

0.0 0

1.0

1

2 strain(%)

3

Display

Power supply

0

4

1

e)

2 strain(%)

3

50 40

40 30 20 10

30

f)

8

0

0

DAQ board

Output voltage(v)

E- Bandage

2

2

3

4

Time (sec)

5

6

Time (sec)

1 finger

off

60

off

off Finger 2 bending

off

off

40

Finger 1 bending

2 finger 3 finger 4 finger

Finger 3 bending

Finger 4 bending

No bending

30 20 10

0

Switching circuit

1

70

No bending

4

0

600 1200 1800 2400 3000 3600

50 6

0

20

4

10

50

10

length of 1.6 cm

0.0

Output Voltage (v)

d)

1.5

0.5

0.5

60

c)

width of 0.3 cm width of 0.6 cm width of 0.9 cm

Resistance(ohm)

a) 3.0

R/R0

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


Resistance(ohm)

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0

5

10 time(sec)

15

20


0 0

2

4

6

8

10 12 14 16 18 20

Time(sec)


a)

60

1 point

50

3 point

2 point

1 point

2 point

1 point

2 point

Output voltage(v)

3 point

1 point

3 point

40

3 point

30 20 10 0

2 point

0

10

20

30

40

Time(sec)

60

b)

1 point 2 point 3 point 4 point

Output voltage(v)

50

1

2 3

4

40 30 20 10 0 0

c)10

5

10 15 20 Time(sec)

25

30

d)

10

8

8

Output voltage(v)

6 R/R0

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

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4 2 0

6 4 2 0

0

1

2 3 Time (sec)

4

5

0

2

4

6

Time(sec)


8

10

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4

a)

Water NaCl 0.5 mol/L

3 R/R0

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


2 1 0

b)

0

20

No bending

40 60 80 Time (hour) Bending

100

120

No bending

Water

on

off

on



3.0

CNT: AgNPs = 5:5 CNT: AgNPs = 7:3 CNT: AgNPs = 9:1

2.5 2.0 R/R 0

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

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1.5 1.0 0.5 0.0 0

1

2 Strain (%)

3


4

Waterproof Electronic-Bandage with Tunable Sensitivity for

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