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Abstract This paper presents a 35.0 × 35.0 × 2.7 mm3 compact, low-profile, and lightweight wearable antenna for on-body wireless power transfer. The proposed antenna can be easily printed on a piece of flexible tattoo paper and transformed onto a PDMS substrate, making the entire antenna structure conform to the human body for achieving a better user experience. Here, a layer of frequency selective surface (FSS) is inserted in between the antenna and human tissue, which has successfully reduced the loading effects of the tissue, with 13.8 dB improvement on the antenna gain. Also, the operating frequency of the rectenna is not affected much by deformation. To maximize the RF-DC conversion efficiency, a matching loop, a matching stub, and two coupled lines are integrated with the antenna for tuning the rectenna so that a wide bandwidth (~ 24%) can be achieved without the use of any external matching networks. Measurement results show that the proposed rectenna can achieve a maximum conversion efficiency of 59.0% with an input power of 5.75 μW/cm2 and can even exceed 40% for a low input power of 1.0 μW/cm2 with a 20 kΩ resistive load, while many other reported rectennas can only achieve a high PCE at a high power density level, which is not always practical for a wearable antenna.

Ionic polymer-metal composite (IPMC) is a promising biomimetic actuator that has received significant attention due to its remarkable high-strain electromechanical performances under low stimulated voltage. Most importantly, it is able to operate in aqueous environment. Nonetheless, the actuation force of the IPMC deteriorates when the applied strain gets too large, which has limited its applications practically. This work has introduced a novel approach that can be used to design crenellated structure on an IPMC actuator for improving its mechanical strength. Numerical simulation has been conducted to optimize the crenellate ratio for achieving larger blocking force and tip deflection. Experimental data has confirmed that the IPMC with the crenellate ratio of 2:3 can improve the blocking force as much as ∼70% and the tip deflection for at least 360%, being much better than the non-crenellated IPMC structure. Dynamic tests were performed at 1 Hz frequency to validate the actuator’s operation in water and air media. The newly proposed crenellated structure can improve the IPMC performances significantly, and it will surely broaden the range of possible applications of the IPMC actuator. [ABSTRACT FROM AUTHOR]

This paper reports a radio-frequency controlled ionic polymer metal composite (IPMC) actuator for aqueous environment. The actuator can be activated through magnetic resonant coupling when the frequency of an external field is tuned to match with the resonant frequency (∼13.6 MHz) of the antenna of the planar receiver. A polydimethylsiloxane based drug reservoir, which has an IPMC actuator integrated, is developed. Under wireless activation, the IPMC actuator unseals the reservoir to initiate drug releases to the aqueous surroundings. The concentration of the released solution was experimentally characterized using a fluorescent microscope well plate reader with the release of the fluorescein dye from a 0.072 ml reservoir by wirelessly activating the actuator with an RF power of 0.65 W. In vitro study was further performed by wireless releases of tetracycline hydrochloride to an Escherichia-coli (E. coli) suspension. The reduction of E. coli colony formation from 89 × 106 to 35 × 106 CFU ml−1 shows that proof of concept on wireless drug delivery was successfully demonstrated. [ABSTRACT FROM AUTHOR]