Dušan Praslička

Possibilities of Measuring Stress and Health Monitoring in Materials Using Contact-Less Sensor Based on Magnetic Microwires

This paper deals with the possibilities of contactless stress measuring inside a material. Conventional strain gauge measuring methods cover surface stress measuring, however measuring inside in material is widely limited. Magnetic microwires give us the ability to create a build-in sensor inside the material without its structure violation. Moreover, sensor can measure several parameters simultaneously, what makes this technology very interesting for many applications.

Influence of Fixation on Magnetic Properties of Glass-Coated Magnetic Microwires for Biomedical Applications

The control of biomechanical processes in the tissue-implant interface and thermal changes created by friction or inflammatory processes in the implant and its environment represent the key validating processes of the postimplanting process. It is crucial for a patient and their health to minimize the invasiveness of the temperature measuring processes and the inner mechanical stress in the implant-tissue interface. For the purpose of these measurements, amorphous magnetic glass-coated microwires are the most suitable. Compared with other sensors, such as radio frequency identification sensors, the microwires have a significant advantage due to their dimensions (~2 cm × 50 μm) (because of which the sensor almost does not interfere with the inner implant structures), their production is relatively cheap, and only ~ 20 mm microwire is needed for the functional sensor. This paper is concerned with the testing of more types of microwire fixation in an implant and the impact of the fixation; it deals with necessary magnetic properties of a microwire and their dependence on the temperature. Microwire made of master alloy Fe78W5B17 was created and fixed in four ways: 1) on one end; 2) on two ends; 3) in the middle; and 4) along its full length. The results show that the optimal way of fixation is the one along the full length of a microwire; however, the final signal is influenced by both, the type and volume of the applied fixation material. The highest sensitivity of the designed microwire was in the range of 120-140 °C with no fixation and only with the full length fixation, this sensitivity decreased to 40-50 °C, which is a level close to the level required for biomedical applications (35-42 °C).

Melt-Spun Fe–Co–B–Cu Alloys With High Magnetic Flux Density for Relax-Type Magnetometers

Melt-spun Fe63 Co21 B15Cu ribbons were annealed at temperatures between 573 K and 623 K in longitudinal and transverse-magnetic field in order to prepare a representative set of relaxed amorphous and partially crystallized samples having uniaxial anisotropy. The optimal magnetic characteristics for the relaxation sensor were obtained after longitudinal field annealing for 1 h at 593 K, which corresponds to early crystallization stage in the heat treated amorphous material. The magnetic flux density after such heat treatment reaches 1.83 T and the value of coercive field is 4.2 A/m. The corresponding relaxation characteristics obtained by using ferroprobe designed as a flat, double-layer coil tightly surrounding the ribbon core with the dimensions of 60 × 3 mm show good prospects for the potential use of these alloys as core materials in the relax-type fluxgate magnetometers mainly due to the extending of their linear measuring range as compared to the currently used commercial materials while keeping the similar sensitivity.

Application of Magnetic Microwires in Titanium Implants - Conception of Intelligent Sensoric Implant

The idea of intelligent sensoric implant which enables to scan parameters from the human body wireless comes from analysis of studies descrbing reasons of implants rejection or loosening. Inflamations and incorrect biomechanical load are offen the reasons for surgery, where implant has to be removed or replaced. Presented study shows a concept of intelligent dental implant, where magnetic microwires are placed and fixed into titanium dental implant to get parameters from implant, tissue, or implant-tissue interaction. A part of the study shows preparation of magnetic microwires, measurement of physical quantities using bistabile magnetic microwires and realisation of the functional model of the sensor and experiments. Obtained results show, that utilization of magnetic microwires in implants for scanning of selected physiological or physical parameters is promising. The further researches in the field of fabrication technology, magnetic wires preparation and scanning processes to confirm an intelligent sensoric implant concept is necessary.

A relax type magnetic fluxgate sensor

Abstract This paper is a contribution to the special fluxgate sensors. It provides an additional mathematical model of a versio of a sensor already published (D. Praslicka, IEEE Trans. Magn., 30 (1994) 934). It is a sensor fearturing an amorphous ferromagnetic alloy core. As the output signal characteristics of rectangular waveform have a pulse width proportional to the intensity of the magnetic field, this belongs to the class of digital sensors. A magnetometer for digital analysis of magnetic field is presented as vector magnetic analyser VEMA. Some experimental results selected from a number of experiments to illustrate the wide range of applications are shown.

Magnetically Bistable Microwires: Properties and Applications for Magnetic Field, Temperature, and Stress Sensing

Amorphous glass-coated microwires with positive magnetostriction are characterized by the magnetic bistability where the switching between the two stable magnetic states appears at the switching field. The switching field is sensitive to the external parameters like magnetic field, temperature, mechanical stress, etc., which gives us possibility to employ the microwires as a miniaturized sensing elements for the mentioned parameters.

Possibile Applications of Magnetic Microwires in Aviation

Abstract Magnetic microwires have been rediscovered due to a number of the unusual magnetic properties and their potential applications. The paper concerns glass-coated magnetic microwires composed of a ferromagnetic metallic core with a diameter of 0.6 - 30 jj.m and of a glass coat with a thickness of 2 - 20 jj.m. The fabrication process and magnetic properties of these microwires are described. Due to their unique properties microwires can be used as a sensing element of sensors. Microwire-based sensors can be used in a wide range of aviation applications as magnetic field sensors, tensile stress sensors or temperature sensors. The main advantages of microwire-based sensors are associated with their small dimensions and weight, which play a very important role in aviation.

Advanced Magnetic Materials for Aeronautics

Abstract In the field of magnetic sensors, magnetic microwires with positive magnetostriction are the materials of the future. Their mechanical and magnetic properties render them ideal materials for applications in aeronautics. A single microwire with a 40 jj.m diameter and a length of 10 mm is capable of capturing information about tensile stresses, magnetic fields, temperature and distance. This information is carried by a parameter called the Switching Field, HSW, which is specific for different types of microwire. Numerous physical qualities affect the HSW and through sensing of HSW, these qualities may be quantified. (A number of physical qualities affecting HSW can be sensed and quantified by means of a contactless induction method.) What distinguishes the system developed by the present authors from other measuring systems based on magnetic microwires is the positioning of a microwire outside the coil system. Thanks to this improvement it is possible to use microwires embedded directly in the construction material. Small dimensions microwires do not damage the structure of the construction material. The absence of a galvanic connection makes this technology even more interesting compared with traditional forge gauges. Offering the possibility of the simultaneous measuring of four parameters, this technology can be used in a wide range of aviation applications. Measurements of an external magnetic field can be usedfor the navigation and stabilization of an aerial vehicle. Tensile stress and distance measuring can be helpful to understand some processes occurring under the surface of the construction material and also to perform fatigue monitoring or structure load monitoring. Another big advantage of magnetic microwires is the low price. Just 1 gram of base material is sufficient to prepare about 40 km of microwire. All these features combine to offer us a material ideal for Smart Sensors, possibly available for use in the near future.