Abstract

Interest in the development of sensors for the detection of magnetic field has never stopped growing, given the wide range of applications that can be addressed.

Surface acoustic waves (SAW) devices are key components in communication systems and have the advantage of being robust, small, passive, wireless and even package-less in specific configurations. To make it sensitive and selective for a physical magnitude while being insensitive to other environmental magnitudes, the judicious choice of the constituent materials is the key step preceding its realization. In our case we focus on the development of magnetic SAW sensors (MSAW) and we will use multilayer structure made of smart materials to meet different requirements. For sensitivity, we will use a layer of magnetoelastic material, micro-structured or not. For the transduction, we will use piezoelectric substrates and to eliminate the effects of temperature we will add dielectric layers which will ensure the compensation by considering the properties of the other constituent layers. Combined with magnetoelastic layer, SAW sensor could exhibits a controlled sensitivity to magnetic field intensity and direction.

In this lecture, an overview of general principle of the MSAW sensors in wired and wireless configurations and developments needed to implement this technology will be given. A review of recent works including from our group will be presented by positioning them with respect to the state of the art. The sensitivities, detection limits and range of detection will be specified for each structure and configuration considered. Finally, and depending on MSAW performances, examples of potential applications in the field of industry, biomedical, energy, transport, etc. will be proposed and analyzed together with an outlook of what MSAW technology can bring.

Keywords: Piezoelectric material, Magnetoelastic material, magnetostrictive material, magnetic sensor, SAW.

Abstract

Toward developing cyber-physical system, an interest for a molecular recognition electronics, which electrically detect and discriminate molecules, is rapidly increasing for collecting chemical information in our daily life. Among various sensor technology, artificial olfactory sensor targeting on chemical data of odor, i.e. volatile molecules, is growing research field due to its promise in wide applications for non-invasive medical diagnosis, environmental monitoring, factory automation, security, smart agriculture, etc. Odors are composed of multiple volatile molecules, so collecting, analyzing and learning digitized odor data through a long-term molecular sensing provide a new approach to clarify unknown complex phenomena, which cannot be understood only by physical information. For such perspective, technology to comprehensively detect and analyze volatile molecules is demanded.

In this talk, I present our odor digitization study and its promise. Starting from the feasibility study of machine-learning based odor molecular analysis in a gas chromatography-mass spectrometry, research is expanded to ones with artificial olfactory sensor array. As an example of value creation using odor information, breath odor sensing based biometric authentication is demonstrated. Also, challenging issues and our efforts towards practical application of artificial olfactory sensor are also introduced.

Keywords: chemiresistive sensor, artificial olfactory sensor, odor digitization

Abstract

The application of gas sensors is extremely extensive, so the interest in them is still thriving.

Among numerous gas sensing technologies, surface acoustic wave (SAW) technology exhibits unique advantages such as high sensitivity, fast response, wide range, and micro/nano scale, which has aroused widespread research interest. In fact, the development of SAW technology can be traced back to the study of seismic waves by British physicist Raleigh in the 1880s. But it was not until the mid-20th century that White et al. invented a interdigital transducer deposited on the surface of piezoelectric crystals, which successfully stimulated the propagation of SAW along the surface of piezoelectric crystals using the piezoelectric effect, and opened the door to the practical application of SAW technology.Until today, SAW devices remain an indispensable key signal processing component in fields such as mobile communication. In addition, due to the propagation of SAW along the crystal surface, they are extremely sensitive to surface disturbances. Based on this characteristic, the development of SAW sensing technology has flourished like mushrooms after rain, and is widely used for sensing temperature, mechanics, magnetic fields, and gases.

The typical structure of SAW gas sensors is composed of SAW devices patterned by delay-line or resonator, and sensing materials deposited along the acoustic propagation path. The reversible and selective adsorption toward target gas molecules in sensing materials modulates the SAW propagations, and induces the changes in SAW velocity or attenuation. By decoupling it, gas information can be obtained. This lecture will combine laboratory research results, starting from the principle of SAW gas sensing, and focus on introducing the response mechanism and design of gas sensing materials, modeling and analysis of SAW gas sensing mechanism based on the multiphysics coupling, optimization design and preparation of SAW sensing devices, and the application of SAW gas sensors in typical gases such as hydrogen and carbon dioxide.

Keywords: Gas sensor, multiphysics coupling, SAW, sensing materials, sensing device.