ABSTRACT
Visualization of training effectiveness is critical to patients' confidence and eventual rehabilitation. Here, an innovative magnetoinductive pressure sensor is proposed for monitoring hand rehabilitation in stroke hemiplegic patients. It couples the giant magneto and stress-impedance effects of a square spiral amorphous wire with the giant magnetoelastic effect of a polymer magnet (NdFeB@PDMS). The addition of the magnetoelastic layer results in a sensitivity improvement of 178%, a wide sensing range (up to 1 MPa), fast response/recovery times (40 ms), and excellent mechanical robustness (over 15 000 cycles). Further integration with an LC oscillation circuit enables frequency adjustment into the MHz range resulting in a sensitivity of 6.6% kPa-1 and outstanding linearity (R2 = â 0.99717) over a stress range of up to 100 kPa. When attached to a commercial split-fingerboard, the sensor is capable of dynamically monitoring the force in each finger, providing a reading of the rehabilitation process. Unlike conventional inductive sensors, the sensor is based on an inductive force-responsive material (amorphous wire), which significantly boosts the sensitivity. The approach also demonstrates the potential of magnetoelasticity in static pressure sensing, which is highly sensitive to dynamic pressure only through electromagnetic induction. This makes it more suitable for long-term and continuous human health monitoring.
ABSTRACT
In this paper, carbon-encapsulated nanoparticles of iron and iron nitride were synthesized using ferrocene by reactive radio-frequency thermal plasma. The properties of the prepared nano-powders were investigated by TEM, XRD, Raman spectroscopy and VSM. The samples obtained with zero-nitrogen plasma, contains the carbon-encapsulated iron nanoparticles. There cores mainly composed of ferromagnetic α-Fe and paramagnetic γ-Fe, with carbon shell thicknesses of about 5 nm. The samples synthesized by the plasma with varying nitrogen flow rates, mainly consists of iron nitride and oxide having spherical and irregular shape with deteriorated and disappearing carbon shell. Particle size in all samples were 20-90 nm. Synthesized sample at zero-nitrogen condition showed a room-temperature saturation magnetization of 19.65 emu/g, with a coercivity of 375.1 Oe. The sample prepared with optimal nitrogen flow rate had a saturation magnetization of 35.25 emu/g at room temperature, with a coercivity and remanence of 49.1 Oe and 0.56 emu/g, respectively.
ABSTRACT
The objective of this study was to deposit thin films on PET polymer substrate and examine the functional properties systematically. Their properties have been studied as a function of the N2-Ar flow rates, deposition time span and Cu doping. Iron nitride film deposited on both sides exhibits ferromagnetic phases, γ'-Fe4N and ε-Fe3N co-existed, shows negligible magnetic anisotropy. Other samples show the evolution of N-rich (FeN, Fe2N) and N-poor (Fe16N2, Fe3N, Fe4N) phases under different deposition time conditions. XPS analysis and free energy calculations confirmed that co-sputtered Fe-Cu thin films are more stable than layer deposited counterparts. From VSM results it is evident that the dominant phase, changes steadily from the ferromagnetic α-Fe (N) to the paramagnetic ξ-Fe2N with the increase of nitrogen flow rates and the ordering of the nitrogen atoms. Binding energy increases steadily from 733 eV to 740 eV with the increasing thickness of thin films from 74 nm to 94 nm. It was observed that surface energy decreases as the contact angle of glycol increases and changes the thin film surface from polar to nonpolar. TEM images indicate that cubic γ'-Fe4N and ε-Fe3N nano particles oriented in preferred directions dispersed uniformly in the amorphous iron nitride matrix.
