EUROSENSORS XVII : book of abstracts

Fundação Calouste Gulbenkien (FCG).Fundação para a Ciência e a Tecnologia (FCT)

Soft Materials for Wearable/Flexible Electrochemical Energy Conversion, Storage, and Biosensor Devices

none6Next-generation wearable technology needs portable flexible energy storage, conversion, and biosensor devices that can be worn on soft and curved surfaces. The conformal integration of these devices requires the use of soft, flexible, light materials, and substrates with similar mechanical properties as well as high performances. In this review, we have collected and discussed the remarkable research contributions of recent years, focusing the attention on the development and arrangement of soft and flexible materials (electrodes, electrolytes, substrates) that allowed traditional power sources and sensors to become viable and compatible with wearable electronics, preserving or improving their conventional performances.openBocchetta, P.; Frattini, D.; Ghosh, S.; Mohan, A.M.V.; Kumar, Y.; Kwon, Y.Bocchetta, P.; Frattini, D.; Ghosh, S.; Mohan, A. M. V.; Kumar, Y.; Kwon, Y

Developing new chemical-based sensors for the detection of volatile compounds

This research project aims to enhance the performance of a series of chemical-based sensor devices. In particular, metal oxide gas sensors. These materials are well known and primarily employed in several applications, thanks to their characteristic of interacting with volatile compounds, giving a response in terms of reversible change in the electrical resistance. Another exciting feature of metal oxide semiconductors, in particular rare earth-dope ones, is represented by their cataluminescence (a type of light emission when they interact with certain volatile compounds). We attempt to register simultaneously and combine the two different sensor responses (electrical resistance and light emission) to enhance sensor sensitivity and selectivity. This mode of operation can be defined as "dual-modality", and it represents a novel approach to sensor technology.For this purpose, the first part of the research project involved the synthesis and the characterisation of metal oxide nanoparticles to be employed in the sensing experiments. Afterwards, the materials obtained were used as sensing elements in in-house made equipment, recording the electrical resistance and the cataluminescence simultaneously. We tested each material under investigation with the following volatile compounds: acetone, ethanol, hydrogen peroxide, nitroglycerine, ethylene glycol dinitrate, 2,3-dimethyl-2,3-dinitrobutane, 2,4-dinitrotoluene and triacetone triperoxide. The experiments were repeated at different sensor temperatures in the range of 150-400°C. These ensured a full screening of the operating conditions and, consequently, the possibility of identifying the best parameters to ensure optimal sensor performance.The results obtained are encouraging in terms of sensor performances. In particular, the europium-doping of the zirconium oxide gas sensor allowed achieving a higher cataluminescence production, especially in the temperature range 250-275°C, and consequently a better sensor sensitivity. Recording the light emission simultaneously with the resistance response was shown to be very promising in terms of selectivity. If two given compounds showed a similar response in terms of resistance, discrimination is still possible thanks to their different cataluminescence response profiles.This thesis work showed for the first time and promisingly the possibility of combining more than one response from a single sensor to enhance its performance. We found out that the dual-modality can increase the sensor's possibility to distinguish among different volatiles. Especially the doping with rare earth metals, such as europium, increased the general response and consequently, they represent a promising material for the employment of dual-modality sensing

PHENOMENA AND MECHANISMS OF PHOTOVOLTAIC EFFECTS IN FERROELECTRIC BIFEO3 THIN FILMS

Ph.DDOCTOR OF PHILOSOPH

A hybrid piezoelectric and electrostatic energy harvester for scavenging arterial pulsations

Implantable and wearable biomedical devices suffer from a limited lifespan of on-board batteries which results in a requirement to change the battery or the device itself causing additional physical discomfort. In order to overcome this, various energy harvesters have been developed. The human body possesses several types of energy available for scavenging through appropriately designed energy harvesting devices, while cardiovascular system in particular represents a constant reliable source of mechanical energy from vibration. Most conventional energy harvesters exploit only a single phenomenon, such piezo- or triboelectricity, thus producing reduced power density. As an improvement, hybridisation of energy harvesters intends to negate this drawback by simultaneously scavenging energy by multiple harvesters. In the present work, the reverse electrowetting on dielectric (REWOD) phenomenon is combined with the piezoelectric effect in a proof-of-concept hybrid harvester for scavenging biomechanical energy from arterial or other type pulsations. A mathematical model of the harvester was developed, and a computational investigation using CFD, and fluid-structure interaction simulations were carried out using the COMSOL Multiphysics software. The effect of the materials of piezoelectric film and geometrical features of the harvester on parameters such as the displacement, the frequency of pulsations and the energy produced were studied. An experimental setup that could imitate the displacements caused from arterial pulsations was designed and the produced electrical energy characteristics were analysed. A comparison between experimental and computational data was carried out and demonstrated a good agreement. Dependencies between geometrical parameters and electrical output were obtained, recommendation on piezoelectric materials and design solutions were provided

Recent progress in piezotronic sensors based on one-dimensional zinc oxide nanostructures and its regularly ordered arrays: from design to application

Piezotronic sensors and self-powered gadgets are highly sought-after for flexible, wearable, and intelligent electronics for their applications in cutting-edge healthcare and human-machine interfaces. With the advantages of a well-known piezoelectric effect, excellent mechanical properties, and emerging nanotechnology applications, one-dimensional (1D) ZnO nanostructures organized in the form of a regular array have been regarded as one of the most promising inorganic active materials for piezotronics. This report intends to review the recent developments of 1D ZnO nanostructure arrays for multifunctional piezotronic sensors. Prior to discussing rational design and fabrication approaches for piezotronic devices in precisely controlled dimensions, well-established synthesis methods for high-quality and well-controlled 1D ZnO nanostructures are addressed. The challenges associated with the well-aligned, site-specific synthesis of 1D ZnO nanostructures, development trends of piezotronic devices, advantages of an ordered array of 1D ZnO in device performances, exploring new sensing mechanisms, incorporating new functionalities by constructing heterostructures, the development of novel flexible device integration technology, the deployment of novel synergistic strategies in piezotronic device performances, and potential multifunctional applications are covered. A brief evaluation of the end products, such as small-scale miniaturized unconventional power sources in sensors, high-resolution image sensors, and personalized healthcare medical devices, is also included. The paper is summarized towards the conclusion by outlining the present difficulties and promising future directions. This study will provide guidance for future research directions in 1D ZnO nanostructure-based piezotronics, which will hasten the development of multifunctional devices, sensors, chips for human-machine interfaces, displays, and self-powered systems