Aims: Recent advancements in sensing technology and wireless communications have accelerated the development of the Internet of Things (IoT) which promote the usage of wearable sensors. An emerging trend is to develop self-sustainable wearable devices, thus eliminating the necessity of the user to carry bulky batteries. In this work, the development of a flexible piezoelectric energy harvester that is capable of harvesting energy from low frequency vibrations is presented. The target application of this energy harvester is for usage in smart shoes. Objectives: The objectives of this research is to design, fabricate and test an energy harvester on PET substrate using Aluminum Zinc Oxide as its piezoelectric layer. Methods: The energy harvester was designed as a cantilever structure using PET/AZO/Ag layers in d33 mode which can generate large output voltages with small displacements. The electrodes were designed as an interdigitated structure in which two significant design parameters were chosen, namely the effect of gap between electrodes, g and number of interdigital electrodes (IDE) pairs, N to the output voltage and resonant frequency. Results: The sputtered AZO on PET showed c-axis orientation at 002 peak with 2 values of 34.45° which indicates piezoelectric behaviour. The silver IDE pairs were screen-printed on the AZO thin film. Functionality of the device as an energy harvester was demonstrated by testing it using a shaker. The energy harvester was capable of generating 0.867 Vrms output voltage when actuated at 49.6 Hz vibrations. Conclusion: This indicates that the AZO thin films with printed silver electrodes can be used as flexible, d33 energy harvesters.

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In this paper, a compact wearable antipodal Vivaldi antenna resonating at 3.5 GHz is proposed for 5G n77 and n78 bands. It is designed on a flexible polyester substrate with a dielectric constant (ɛr) of 2 and loss tangent (tan δ) of 0.005. The antenna parameters were optimized via parametric analyses using CST software with a size of 33 × 33 mm 2 (length × width). The antenna is evaluated in terms of reflection coefficient (S11), gain, efficiency, radiation pattern and surface current density and itsreflection coefficient is verified with measurement. This antenna attained a maximum simulated gain of 4.17 dBi and an efficiency of 98.18 % in the resonating band.

In this paper, a dual band wearable antenna for 5G applications that resonates at 3.63 GHz and 4.95 GHz covering sub-6 GHz 5G-NR bands such as n48, n77, n78, and n79 is presented. The antenna consists of slotted circular ring patch as radiating element, polyester as wearable substrate, and a partial ground plane on the bottom. The designed antenna is sized at 55×46×0.4 mm 3 , achieving a bandwidth of 300 MHz from 3.50 to 3.80 GHz and a bandwidth of 160 MHz from 4.86 to 5.02 GHz. Besides, the antenna shows realized gain of 4.2 dBi at 3.63 GHz and 5.78 dBi at 4.95 GHz whereas efficiency is found 90.5 % and 82.3 % respectively.

Zinc batteries are a more sustainable alternative to lithium-ion batteries due to its components being highly recyclable. With the improvements in the screen printing technology, high quality devices can be printed with at high throughput and precision at a lower cost compared to those manufactured using lithographic techniques. In this paper we describe the fabrication and characterization of printed zinc batteries. Different binder materials such as polyvinyl pyrrolidone (PVP) and polyvinyl butyral (PVB), were used to fabricate the electrodes. The electrodes were first evaluated using three-electrode cyclic voltammetry, x-ray diffraction (XRD), and scanning electron microscopy before being fully assembled and tested using charge-discharge test and two-electrode cyclic voltammetry. The results show that the printed ZnO electrode with PVB as binder performed better than PVP-based ZnO. The XRD data prove that the electro-active materials were successfully transferred to the sample. However, based on the evaluation, the results show that the cathode electrode was dominated by the silver instead of Ni(OH)2, which leads the sample to behave like a silver-zinc battery instead of a nickel-zinc battery. Nevertheless, the printed zinc battery electrodes were successfully evaluated, and more current collector materials for cathode should be explored for printed nickel-zinc batteries.