Environmentally resilient antimicrobial coatings are becoming increasingly required for a wide range of applications. For this purpose, nanocomposite thin films of poly(vinylidene fluoride) (PVDF) filled with several types of functionalized nanodiamonds (NDs) were processed by solvent casting. The effects of ND inclusion and functionalization in their morphological, structural, optical, thermal, and electrical properties were evaluated taking into account the type of the nanofiller and a concentration up to 2 wt %. The morphology, structure, and thermal features of the polymer matrix are governed by the processing conditions, and no noticeable changes occurred due to the presence of the ND fillers. The polymer crystallized mainly in the α phase with a crystallinity of ≈60%. In turn, the optical transmittance from 200 to 800 nm and the dielectric constant effectively depended on the ND type and content. The inclusion of the ND particles effectively provided antimicrobial properties to the films, which depended on the ND functionalization. This study thus shows that the incorporation of functionalized NDs into PVDF allows the development of antimicrobial coatings with tailorable optical and dielectric properties, which could be of great importance to face nowadays pandemic crisis scenario.

Rapid technological developments in biomedicine, sensors, actuators and energy areas are taken place in the context of the global digital transformation, supported by the “Industry 4.0″ and “Internet of Things” (IoT) concepts. Those developments must include circular economy considerations in the scope of the 2030 sustainable developments goals to ensure easy access to affordable, sustainable, reliable, and modern services for all. To fulfil these advances, materials with high-performance based on biopolymers with tailored dielectric, magnetic and conducting properties are needed for improving devices performance while reducing environmental impact. Within this scope, bio-based resources are considered as next-generation materials for a broader range of applications. In this context, we present on the molecular structure, organization, main physical-chemical and functional properties of the most promising biopolymers. Further, the various possible modifications and processing methods are discussed to reach specific morphological, structural and/or functional characteristics. Finally, bio polymers-based blends and composites are discussed, alongside with their main application areas, opportunities, and challenges.

With the evolution of the digital society, the demand for miniaturized multifunctional devices has been increasing, particularly for sensors and actuators. These technological translators allow successful interaction between the physical and digital worlds. In particular, the development of smart materials with magnetoelectric (ME) properties, capable of wirelessly generating electrical signals in response to external magnetic fields, represents a suitable approach for the development of magnetic field sensors and actuators due to their ME coupling, flexibility, robustness and easy fabrication, compatible with additive manufacturing technologies. This work demonstrates the suitability of magnetoelectric (ME) responsive materials based on the magnetic ionic liquid (MIL) 1-butyl-3-methylimidazolium tetrachloroferrate ([Bmim][FeCl4]) and the polymer poly(vinylidene fluoride-co-trifluoroethylene) (P(VDF-TrFE) for magnetic sensing and actuation device development. The developed sensor works in the AC magnetic field and has frequency-dependent sensitivity. The materials show voltage responses in the mV range, suitable for the development of magnetic field sensors with a highest sensitivity (s) of 76 mV·Oe−1. The high ME response (maximum ME voltage coefficient of 15 V·cm−1·Oe−1) and magnetic bending actuation (2.1 mm) capability are explained by the magnetoionic (MI) interaction and the morphology of the composites.

A naturally derived polymer based on iota carrageenan and different ammonium and imidazolium based ionic liquids (ILs) are used for the development of environmentally friendly soft actuators. The influence of IL content and type and solvent evaporation temperature on the morphological and physico-chemical properties of the materials was evaluated, together with the effect on actuator functional response. Independently of the IL content and type, and the solvent evaporation temperature, a non-porous structure is obtained. The incorporation of the IL within the polymer matrix does not affect the thermal stability but leads to a decrease in the Young modulus for the different IL/carrageenan samples. The highest influence was observed by using the [Ch][DHP] IL at a filler content of 40% w/w with a decrease in the Young modulus from 748 MPa for the neat polymer to 145 MPa for the [Ch][DHP]/carrageenan sample. Furthermore, the ionic conductivity of the samples increases with increasing IL content, with the highest values being 2.9 × 10-6 S cm-1 and 1.2 × 10-6 S cm-1 for the samples with 40% w/w of [Bmim][FeCl4] and [Ch][DHP], respectively. Regarding the soft actuator performance, the maximum displacement was obtained for the [Ch][DHP]/carrageenan sample with an IL content of 40% w/w, showing a maximum displacement of 5.8 mm at a DC applied voltage of 9 V.

Humidity sensors are required in different fields, including industry (e.g., food processing and textiles), environment monitoring, biomedicine, pharmaceuticals, and agriculture, since their design is intrinsically associated with the specific application. Due to their great advantages, polymer-based materials have been strongly employed in the development of humidity sensors for a large variety of applications. For this purpose, both natural and synthetic polymers have been combined with different fillers (e.g., carbon nanotubes, nanoparticles, metal oxides, and ionic liquids), aiming at the development and design of humidity sensing devices. This chapter focuses on different polymer-based humidity sensors and their potential for the development of a new generation of flexible, portable, and wearable systems. The current state of the art and main trends regarding humidity sensor development are presented, based on performance parameters, polymer matrix types, and active fillers.

Polymer composites comprising the ionic liquid (IL) [Bmim][FeCl4] and poly(vinylidene fluoride) (PVDF) have been developed for humidity sensing applications. Different IL contents (5, 10, and 20 wt %) were incorporated into the PVDF matrix and the morphological, physical–chemical and electrical properties of the composites evaluated, together with their humidity sensitivity response. Higher IL contents (20 wt %) induce a porous morphology in the composites. Further, IL incorporation leads to the crystallization of PVDF in the electroactive β phase, which content increases with the incorporation of IL into the polymer. The thermal stability of the composites decreases with increasing IL content. The humidity sensing response of the composites was evaluated with relative humidity variations from 35 to 90%. It is shown that all composites exhibit a linear resistance variation with the relative humidity, the sensitivity to humidity variations increasing linearly with the IL content. The developed materials show a strong potentiality for printable humidity sensors.