An inkjet-printed bendable antenna for wearable electronics
Flexible antennas, which can conform to the skin and transfer signals to terminals, are particularly useful for wearable electronics. Bending, which frequently occurs to flexible devices, significantly affects the performance of flexible antennas. Inkjet printing has been used as an additive manufacturing technology for fabricating flexible antenna in recent years. However, there is little research on the bending performance of inkjet printing antenna in both simulation and experiment. This paper proposes a bendable coplanar waveguide antenna with a small size of 30 × 30 × 0.05 mm3 by combining the advantages of fractal antenna and serpentine antenna, which realizes the ultra-wideband feature and avoids the problems of large dielectric layer thickness (greater than 1 mm) and large volume of traditional microstrip antenna at the same time. The structure of the antenna was optimized by simulation using the Ansys high-frequency structure simulator, and the antenna was fabricated on a flexible polyimide substrate by inkjet printing. The experimental characterization results show that the central frequency of the antenna is 2.5 GHz, the return loss is −32 dB, and the absolute bandwidth is 850 MHz, which is consistent with the simulation results. The results demonstrate that the antenna has antiinterference capability and can meet the ultra-wideband characteristics. When the traverse and longitudinal bending radius are greater than 30 mm and skin proximity greater than 1 mm, the resonance frequency offsets are mostly within 360 MHz, and return losses of the bendable antenna are within the −14 dB compared with the no bending condition. The results exhibit that the proposed inkjet-printed flexible antenna is bendable and promising for wearable applications.
1.Kim Y, Oh JH, 2020, Recent progress in pressure sensors for wearable electronics: From design to applications. Appl Sci
Basel, 10(18):6403.
2. Spanu A, Casula G, Cosseddu P, et al., 2021, Flexible and wearable monitoring systems for biomedical applications in organic flexible electronics: Fundamentals, devices, and applications, in Organic Flexible Electronics, Elsevier, 599–625.
3. Wang L, Xu T, Fan C, et al., 2021, Wearable strain sensor for real-time sweat volume monitoring. iScience, 24(1):102028.
4. Wang LR, Xu TL, Zhang XJ, 2021, Multifunctional conductive hydrogel-based flexible wearable sensors. TracTrends Anal Chem, 134:116130.
5. Pu Z, Zhang X, Yu H, et al., 2021, A thermal activated and differential self-calibrated flexible epidermal biomicrofluidic device for wearable accurate blood glucose monitoring. Sci Adv, 7(5):eabd0199.
6. Liu W, Xie RJ, Zhu JY, et al., 2022, A temperature responsive adhesive hydrogel for fabrication of flexible electronic sensors. NPJ Flex Electron, 6(1):68.
7. Gharbi El, Fernandez-Garcia MR, Ahyoud S, et al., 2020, A review of flexible wearable antenna sensors: Design, fabrication methods, and applications. Materials (Basel),13(17):3781.
8. Nappi S, Miozzi C, Mazzaracchio V, et al., 2021, A plug&play flexible skin sensor for the wireless monitoring of pandemics, in 2021 IEEE International Conference on Flexible and Printable Sensors and Systems (FLEPS), IEEE.
9. Bolaños-Torres MÁ, Torrealba-Meléndez R, MuñozPacheco JM, et al., 2018, Multiband flexible antenna for wearable personal communications. Wirel Pers Commun,100(4):1753–1764.
10. Ramos-Silva JN, Ramírez-García E, Alcántara-Gavilan BA,et al., 2019, Design of a compact ultra wide band flexibleantenna for personal mobile communications, in 2019 IEEE International Fall Meeting on Communications and Computing (ROC&C), IEEE.
11. Alharbi S, Shubair RM, Kiourti A, 2018, Flexible antennas for wearable applications: Recent advances and design challenges, in AP-S International Symposium (Digest) (IEEE Antennas and Propagation Society).
12. Zhang J, Song R, Zhao X, et al., 2020, Flexible grapheneassembled film-based antenna for wireless wearable sensor with miniaturized size and high sensitivity. ACS Omega,5(22):12937–12943.
13. Lou Z, Wang LL, Shen GZ, 2018, Recent advances in smart wearable sensing systems.Adv Mater Technol, 3(12):1800444.
14. Ometov A, Shubina V, Klus L, et al., 2021, A survey on wearable technology: History, state-of-the-art and current challenges. Comput Netw, 93:108074.
15. Sahnoun N, Messaoudene I, Denidni T, et al., 2015, Integrated flexible UWB/NB antenna conformed on a cylindrical surface. Prog Electromagn Res Lett, 55:121–128.
16. Hasan MR, Riheen MA, Sekhar P, et al., 2020, Compact CPW-fed circular patch flexible antenna for super-wideband applications. Iet Microw Antennas Propag, 14(10):1069–1073.
17. Kulkarni J, 2021, Wideband CPW-fed oval-shaped monopole antenna for wi-fi5 and wi-fi6 applications. Prog Electromagn Res C, 107:173–182.
18. Zhong T, Jin N, Yuan W, et al., 2019, Printable stretchable silver ink and application to printed RFID tags for wearable electronics. Materials (Basel), 12(18):3036.
19. Mirzaee M, Noghanian S, Wiest L, et al., 2015, Developing flexible 3D printed antenna using conductive ABS materials, in 2015
IEEE International Symposium on Antennas and Propagation & USNC/URSI National Radio Science Meeting, IEEE.
20. Jilani SF, Abbasi QH, Alomainy A, 2018, Inkjet-printed millimetre-wave PET-based flexible antenna for 5G wireless applications, in 2018 IEEE MTT-S International Microwave Workshop Series on 5G Hardware and System Technologies (IMWS-5G), IEEE.
21. Guo X, Hang Y, Xie Z, et al., 2017, Flexible and wearable 2.45 GHz CPW-fed antenna using inkjet-printing of silver nanoparticles on pet substrate. Microw Optical Technol Lett,59(1):204–208.
22. Hettak K, Ross T, James R, et al., 2013, Flexible polyethylene terephthalate-based inkjet printed CPW-fed monopole antenna for 60 GHz ISM applications, in 2013 European Microwave Conference.
23. Wagih M, Wei Y, Beeby S, 2018, Flexible 2.4 GHz node for body area networks with a compact high-gain planar antenna. IEEE Antennas Wirel Propag Lett, 18(1):49–53.
24. Du ZM, Wong SW, Chen RS, et al., 2022, Wide bandwidth ratio of 10-to-1 CPW-fed whip antenna with improved radiation patterns, in IEEE Transactions on Antennas and Propagation, IEEE.
25. Zou Q, Jiang S, 2021, A compact flexible fractal ultra‐wideband antenna with band notch characteristic. Microw Optical Technol Lett, 63(3):895–901.
26. Yin B, Ye M, Yu Y, 2021, A novel compact wearable antenna design for ISM band. Prog Electromag Res C, 107:97–111.
27. Mattsson V, Ackermans L, Mandal B, et al., 2021, MAS: Standalone microwave resonator to assess muscle quality.Sensors (Basel), 21(16):5485.
28. Ashoke Raman K, 2018, Dynamics of simultaneously impinging drops on a dry surface: Role of inhomogeneous wettability and impact shape. J Colloid Interface Sci,516:232–247.
29. Pu Z, Wang R, Wu J, et al., 2016, A flexible electrochemical glucose sensor with composite nanostructured surface of the working electrode. Sens Actuators B Chem, 230:801–809.