Special Issue on Advances in Flexible Electronics toward Wearable Sensing

Flexible electronics enable the design of wearable sensors that truly conform to the body. The papers in this Special Issue address the latest advances in the field of materials and manufacturing through data analysis for wearable sensing.

Nyabadza et al. provided a comprehensive review of flexible sensors for physiological measurement that use 3D printing, novel nanomaterials, and responsive polymers [1]. The authors identified the most utilised polymers that provide features such as biocompatibility, stretchability, and self-healing ability to resist bending effects. The review gives an overview of both physical and chemical flexible sensors and discusses the requirements of various application areas, considering how current advances in manufacturing can meet these needs.

A study by Khan et al. investigated the impact of bending on the radiation characteristics of flexible antennas. The authors conducted an experimental approach to examine the bending capabilities of flexible antennas on several polymer substrates, including Polyethylene Terephthalate (PET), Polytetrafluoroethylene (PTFE) Teflon, and Polyvinylchloride (PVC), and examined the effect of a range of different frequencies [2]. This work assists in the design choices of polymer materials to ensure their radiation characteristics are not impacted by deformations in the structure due to bending. This is particularly relevant for developing flexible epidermal patches and smart textiles that integrate flexible antennas within the design.

A paper by Moradi et al. investigated a stop band filter implemented on a compact embroidered metamaterial e-textile [3]. The device featured a fully embroidered conductive thread transmission line based on a cotton substrate. The e-textile metamaterial provided a stop band between 2.7 GHz and 4.7 GHz, demonstrating the ability to reject undesired electromagnetic signals along an e-textile.

Nyabadza et al. demonstrated the potential of magnesium nanoparticle inks for creating conductive tracks in flexible electronics. These nanoparticles are produced by Pulsed laser ablation in liquid, whereby nanoparticles are produced from bulk material via the irradiation of the bulk material submerged in a liquid medium [4]. These materials can be printed on flexible substrates for thermal insulation, conductivity enhancement, antibacterial effects, or battery electrodes. The work by Nyabadza et al. investigated the effect of laser processing parameters on the nanoparticle size and colloidal density.

Smart garments have the potential to have a positive impact on population health, and in order to utilise the information gleaned from wearable sensors, robust data analytics are needed. The paper by Yhdego et al. presented a deep learning method for wearable sensor-based fall detection in a real-time setting [5]. This work presented a feasibility study using data from accelerometer and gyroscope data from sixteen body locations to determine the optimal sensor placement for fall detection methods. Falls are a major public health problem, and research in this field could significantly improve health outcomes, mobility, and independence for those at risk of falls.

This Special Issue focuses on works investigating suitable methods of integrating electronics within a textile substrate, including the investigation of materials along with integration methods and the evaluation of wearable properties in combination with electrical and mechanical characteristics. The papers in this Special Issue provide insight into the range of disciplines involved in the development of wearable sensor devices and highlight the opportunities for further development in this field, which has the potential to transform healthcare and promote well-being in many domains.