Jozef Hudák

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).

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.