The effect of bending on laser-cut electro-textile inductors and capacitors attached on denim as wearable structures

In this paper we present the design, fabrication and characterization of electro-textile inductor and capacitor patterns on denim fabric as a basis for the development of wearable e-textiles. Planar coil inductors have been harnessed as antenna structures for the development of Near Field Communication (NFC) tags with temperature sensing capability, while interdigitated electrode (IDE) capacitors have been used as humidity sensors for wearable applications. The effect of bending in the electrical performance of such structures was evaluated, showing variations below 5% in both inductance and capacitance values for bending angles in the range of interest, i.e. those fitting to human limbs. In the case of the fabricated NFC tags, a shift in the resonance frequency below 1.7% was found, meaning that the e-textile tag would still be readable by an NFC- enabled smartphone. In respect of the capacitive humidity sensor, we obtained a minimum capacitance variation of 40% for a relative humidity range from 10% to 90%. Measured thermal shift was below 5% in the range from 10 to 40oC. When compared to the 4% variation due to bending, it can be concluded that this capacitive structure can be harnessed as humidity sensor even under bending strain conditions and moderate temperature variations. The development and characterization of such structures on denim fabrics, which is one of the most popular fabrics for everyday clothing, combined with the additional advantage of affordable and easy fabrication methodologies, means a further step towards the next generation of smart e-textile products

Electrical Impedance Measurements of DNA Molecules and Gold Nanoparticles at low Temperatures

Strand breaks occur naturally in the deoxyribonucleic acid (DNA) chain. Studies have shown that the amount of breaks increases with exposure to ultraviolet (UV) light. Additionally, it has been shown that low energy electrons, with energies below DNA’s ionization energy, are capable of also inducing strand breaks on DNA. These breaks alter the length of the DNA molecule which in turn alters its electrical impedance. As such, the amount of strand breaks can be indirectly measured through an impedance spectroscopy (IS). This work presents the construction of a cryogenic unit capable to hold an interdigitated sensor, with a sample of DNA or DNA with gold nanoparticles (AuNPs), allowing IS measurements to occur. This cryogenic unit is able to withstand temperatures in the range of 77 to 300 K, while monitoring the temperature at which its sample is. Liquid nitrogen was used as the cold source, allowing the low temperatures mentioned above to be reached. Since the heating process lasts around 8 h, depending on the amount of liquid nitrogen used, it becomes hard to manually start a measurement at the appropriate time. To counter this, a user interface was developed that monitors the temperature, automatically starting a measurement when a temperature defined by the user is reached. Overall, a cryogenic system was built which can be applied in the future for the study of DNA and DNA+AuNPs thin films

A novel multi-frequency trans-endothelial electrical resistance (MTEER) sensor array to monitor blood-brain barrier integrity

© 2021 Elsevier B.V. The blood-brain barrier (BBB) is a dynamic cellular barrier that regulates brain nutrient supply, waste efflux, and paracellular diffusion through specialized junctional complexes. Finding a system to mimic and monitor BBB integrity (i.e., to be able to assess the effect of certain compounds on opening or closing the barrier) is of vital importance in several pathologies. This work aims to overcome some limitations of current barrier integrity measuring techniques thanks to a multi-layer microfluidic platform with integrated electrodes and Multi-frequency Trans-Endothelial Electrical Resistance (MTEER) in synergy with machine learning algorithms. MTEER measurements are performed across the barrier in a range of frequencies up to 10 MHz highlighting the presence of information on different frequency ranges. Results show that the proposed platform can detect barrier formation, opening, and regeneration afterwards, correlating with the results obtained from immunostaining of junctional complexes. This model presents novel techniques for a future biological barrier in-vitro studies that could potentially help on elucidating barrier opening or sealing on treatments with different drugs

Novel gas sensors and electronic noses for optical, electrical and hybrid sensing: development, properties and applications

Smell is one of the most important senses of man. It is used in everyday life, influencing our behaviour. Evaluation of the quality of food and beverages or the production control in industries that require specialised personnel, are some examples of its use. The Electronic Nose mimics the human nose, through the transduction of a chemical interaction between a sensitive layer and the volatile compounds, generating a measurable signal. Conducting polymers, doped with dodecylbenzenesulfonic acid, employed in electrical gas sensors and in an electronic nose showed their applicability in monitoring the circadian emissions of fragrance by the plant Madagascar Jasmin and in the discrimination and classification of different samples of flaxseed, respectively. An innovative approach in the development of sensitive thin films based on organized liquid crystal micelles in an ionic liquid, encapsulated in a biopolymer matrix and used as sensitive layers for gas sensors, is the focus of this thesis. Liquid crystal micelles acting as sensitive elements that change reversibly their orientation in the presence of volatile compounds showed, as a proof of concept, their potential use in the classification of volatile solvents. They were also successfully tested for monitoring the quality of Tilapia fish. The combination of this optical system with the electrical system gave the so called "hybrid sensor" with dual response. Thus, a single sensor was efficient in the quantification of ethanol in gasoline. Polarized light microscopy, SEM and AFM techniques were used to study the morphology of these layers and have revealed that the formation of the micelles is closely influenced by the solvent where the liquid crystal molecules are arranged. QCM studies were conducted in order to learn more about the interaction of these films with volatile compounds, and to check the influence of parameters such as the exposure time, solvent nature, film composition and drying time, on the film. These biopolymer films were also used as immobilisation matrix for cytochrome c, forming electrochemical sensors having an additional optical response