Page 113 - IJB-9-4

International Journal of Bioprinting An inkjet-printed bendable antenna for wearable electronics

for wireless communication systems based on antenna substrate. The radiating properties of the antenna were
structures and small sensors [11,12] . The development of investigated. The simulated and measured reflection
electronic devices is trending toward miniaturization, coefficients are ∼−31 dB and ∼−23 dB, respectively.
portability, and intelligence, especially in the field of Meanwhile, the −10 dB bandwidth is ∼530 MHz and
wearable electronics [13,14] . Therefore, in order to meet the the obtained VSWR is ∼1.3. Radiating properties were
developing needs of communication and information characterized and agreed well with the simulation results .
[21]
technology, researches on mobile and flexible antennas Hettak et al. investigated an inkjet-printed millimeter-wave
have been gaining interest. The recent research on flexible antenna on polyethylene terephthalate (PET) substrate.
antenna mainly focuses on the antenna structure design The 60 GHz CPW-fed monopole antenna was printed with
and the methods of manufacturing flexible antenna. a DMP-2800 series inkjet printing system. The measured
impedance bandwidth of the printed antenna, defined by
For antennal structure design, it is required to meet return loss of less than −10 dB, is from 60 to 65 GHz .
[22]
the requirements of compact, multiband and broadband However, in the structural design, it is not possible to
structure design simultaneously to adapt to the trend obtain UWB features while avoiding large dielectric layer
of modern communication system integration and thickness and volume at the same time. In addition, the
wearability. In particular, the wideband flexible antennas, effect of the simulation and experiment on the bending of
which have wider impedance bandwidth, can achieve these previous works has not been studied yet, especially
higher data transmission rates and enable vast applications. under different bending curvatures.
Sahnoun et al. designed an ultra-wideband (UWB)
flexible monopole antenna integrated with a narrow-band This paper proposes a bendable antenna based
rectangular slot . The results showed that the monopole on inkjet printing silver nanoparticles. The bendable
[15]
antenna covers an UWB from 2 to 12 GHz with S less antenna is designed with a center frequency at 2.45 GHz
11
than −10 dB. Hasan et al. proposed a coplanar waveguide and presented a CPW structure with a small size of 30 ×
3
(CPW)-fed flexible antenna with a circular patch , which 30 × 0.05 mm , making it convenient to integrate with
[16]
has UWB performance and a bandwidth ratio of 188.5%. flexible wearable electronics and detect the real-time
Jayshri Kulkarni et al. fabricated a wideband CPW-fed and efficient transmission of epidermis information. By
monopole antenna for Wi-Fi5 and Wi-Fi6 applications . contrasting performance results based on electromagnetic
[17]
The measured wideband operation of 34.5% (5.15– field simulations using Ansys high-frequency structure
7.29 GHz) is obtained by a single resonance at 6.2 GHz, simulator (HFSS), the prototype of the flexible low-profile
conforming to the bandwidth requirement of Wi-Fi5 antenna was obtained. Furthermore, the bendable antenna
and Wi-Fi6. However, these papers did not consider the was fabricated by inkjet printing on flexible polyimide
influence of bending on the antennas. substrate, and its stability was verified using various
measurement setups and performance tests.
There are two common ways to manufacture flexible
antennas. One of the methods is to use flexible fabric as the 2. Materials and methods
substrate and use bonding or embroidery to make flexible 2.1. Antenna structure and models
antennas, while the other is printing technology used to A planar structure is helpful to improve the stability of
prepare flexible antennas on a flexible substrate. The latter the antenna and enlarge the scope of effective work. The
has a mature production mode and excellent antenna resonant frequency of the antenna depends on the electrical
performance, and allows for easy mass production. Printing length of the antenna. The larger the electrical length,
technology includes screen printing , 3D printing , and the lower the resonant frequency. The single-frequency
[18]
[19]
inkjet printing . Inkjet printing has the merit of direct and multifrequency characteristics of the antenna are
[20]
writing and involving no mask, which is widely used in the determined by the symmetry of the antenna vibrator, and
manufacturing of flexible antennas. Jilani et al. proposed the vibrator branches with different lengths can produce
an inkjet-printed millimeter-wave flexible antenna based different resonance frequencies. The designed low-profile
on a polyethylene terephthalate substrate for 5G wireless flexible antenna with a center frequency of 2.45 GHz
applications . The prototype exhibited an impedance determines the complete symmetry of the two arms of
[20]
bandwidth of 26–40 GHz, a consistent omnidirectional the dipolar oscillator. The input impedance of the antenna
radiation pattern, and a peak gain of 7.44 dBi at 39 GHz. depends on its length, width, structure layout, feeding
On the other hand, inkjet-printed CPW-fed bendable position, and mode, while the return loss depends on the
antenna has also been explored through research. Guo et matching degree of the antenna impedance, that is, the
al. demonstrated a fully printed CPW-fed antenna based pure resistance of the input impedance and the proximity
on silver-nanoparticles on the polyethylene terephthalate to the characteristic impedance of the transmission line.

Volume 9 Issue 4 (2023) 105 https://doi.org/10.18063/ijb.722