Research Article: Triboelectric‐Based Transparent Secret Code

Date Published: February 04, 2018

Publisher: John Wiley and Sons Inc.

Author(s): Zuqing Yuan, Xinyu Du, Nianwu Li, Yingying Yin, Ran Cao, Xiuling Zhang, Shuyu Zhao, Huidan Niu, Tao Jiang, Weihua Xu, Zhong Lin Wang, Congju Li.


Private and security information for personal identification requires an encrypted tool to extend communication channels between human and machine through a convenient and secure method. Here, a triboelectric‐based transparent secret code (TSC) that enables self‐powered sensing and information identification simultaneously in a rapid process method is reported. The transparent and hydrophobic TSC can be conformed to any cambered surface due to its high flexibility, which extends the application scenarios greatly. Independent of the power source, the TSC can induce obvious electric signals only by surface contact. This TSC is velocity‐dependent and capable of achieving a peak voltage of ≈4 V at a resistance load of 10 MΩ and a sliding speed of 0.1 m s−1, according to a 2 mm × 20 mm rectangular stripe. The fabricated TSC can maintain its performance after reciprocating rolling for about 5000 times. The applications of TSC as a self‐powered code device are demonstrated, and the ordered signals can be recognized through the height of the electric peaks, which can be further transferred into specific information by the processing program. The designed TSC has great potential in personal identification, commodity circulation, valuables management, and security defense applications.

Partial Text

Smart identification has witnessed the rapid development of signal analyzing, telecommunication, human–machine interaction, and defense system.1, 2, 3, 4 With the growing attention on the mobile payment, cell phones and other intelligent devices have been commonly technological means due to their convenience, portability, and systematical organization by the software.5 However, excessive use of these electronics may increase the burden on the data link system and the risk of information leakage.6, 7 In daily use, there are conditions that require different identification devices, for example, in bank, shop, bus, entrance check, and security system, most of which utilize the magnetic card. But magnetic stripe, the key component, is more likely to be scratched or demagnetized.

The structure of the TSC is illustrated in Figure1a. It was like a bar code with ITO stripes of different lengths. A layer of FEP film was sealed on the top of the polyethylene terephthalate (PET)‐ITO substrate. It can be seen in Figure 1b that the fabricated device was highly transparent to all visible colors on the background of a chromatic rectangle and even invisible when it lay on a black table board, where it is framed by the yellow dashed lines. The transmittance of the device is shown in Figure 1c. It was observed that the bare PET‐FEP piece possessed the highest transmittance which is nearly 93% in visible region, a little higher than the fully covered ITO‐PET substrate sealed by FEP, and the fabricated patterned device is intermediate of which is average 90%. A little decrease of the transmittance was found from 400 to 600 nm due to the absorbance of the ITO electrode.26, 27 The whole device is long and thin, easy to bend, and convenient to take along, which possesses excellent mechanical toughness and is satisfying for daily use. We bent and rolled the as‐fabricated as shown in Figure 1d,e. It recovered easily after removing the external force.

The paper presents a self‐powered sensor with highly recognizable information remained on a transparent and flexible thin film. The device is capable to conform to the shape or the curvature of external substrate for its excellent mechanics. It is the design of the ITO stripes of the device that works to distinguish the relative heights of the electric peaks. For the sliding or roll‐to‐roll motion from one side to the other, the length and interval of the stripes influence the output signals. This TSC is velocity‐dependent and we demonstrate their applications as a self‐powered bar code. The information was acquired by the monitor and processed to compile actual expressions. For practical applications, the cover film is modified to be hydrophobic and can be protected from the water contaminant. The designed TENG has great potential in personal identification, commodity circulation, valuables management, and security defense applications.

Fabrication of the TSC Device: A typical PET film was chosen as the substrate. A layer of ITO was deposited onto the PET (125 µm) substrate by magneton sputtering (PVD75 Kurt J. Lesker). The designed electrodes were molded by the UV photolithography (MA6 SUSS). Then the substrate was treated with etchant to generate the desired pattern, which were connected in series by a straight conductive trace. The FEP (50 µm) film was coated with a thin layer of Cu using the magneton sputtering before it was etched by the ICP plasma (Sentech SI 500). The gases of Ar, CF4, and O2 were inlet into the ICP chamber with flow ratios of 15.0, 30.0, and 10.0 sccm, respectively. The operation chamber pressure was lower than 2 Pa, and the plasma generated power and acceleration power was 200 W and 80 W, respectively. Then the nanostructured FEP film was adhered over the PET substrate.

The authors declare no conflict of interest.




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