The applications of ferrimagnetic oxides, or ferrites, in the last 10 years are reviewed, including thin films and nanoparticles. The general features of the three basic crystal systems and their magnetic structures are briefly discussed, followed by the most interesting applications in electronic circuits as inductors, in high-frequency systems, in power delivering devices, in electromagnetic interference suppression, and in biotechnology. As the field is considerably large, an effort has been made to include the original references discussing each particular application on a more detailed manner.

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Novel Applications of Ferrites

Epidermal electronic systems (EESs) are skin-like electronic systems, which can be used to measure several physiological parameters from the skin. This paper presents materials and a simple, straightforward fabrication process for skin-conformable inkjet-printed temperature sensors. Epidermal temperature sensors are already presented in some studies, but they are mainly fabricated using traditional photolithography processes. These traditional fabrication routes have several processing steps and they create a substantial amount of material waste. Hence utilizing printing processes, the EES may become attractive for disposable systems by decreasing the manufacturing costs and reducing the wasted materials. In this study, the sensors are fabricated with inkjet-printed graphene/PEDOT:PSS ink and the printing is done on top of a skin-conformable polyurethane plaster (adhesive bandage). Sensor characterization was conducted both in inert and ambient atmosphere and the graphene/PEDOT:PSS temperature sensors (thermistors) were able reach higher than 0.06% per degree Celsius sensitivity in an optimal environment exhibiting negative temperature dependence.

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Inkjet-Printed Graphene/PEDOT:PSS Temperature Sensors on a Skin-Conformable Polyurethane Substrate.

A review on MnZn ferrites: Synthesis, characterization and applications.

Inductor–capacitor ( $LC$ ) passive wireless sensors use a transformer with loose coupling between an external readout coil and an inductor that receives power through this inductive coupling. Changes in the sensor are wirelessly and remotely detected by the readout coil, which makes them highly useful in applications that require the sensor to be powered remotely and to occupy a small volume, such as harsh and sealed environments, where physical access to the sensor is difficult. Although the sensor to accomplish this function dates from the 1960’s, its rapid extension over the past decades has benefited from microelectromechanical systems. This paper provides an overview of the status and challenges in the $LC$ passive wireless sensor toward a wireless sensing platform. The basic sensing principles are first categorized into detecting changes of the sensor in response to the capacitance, resistance, inductance, or coupling distance due to the parameter of interest through monitoring the impedance magnitude and phase spectrum. The present state of the art in sensor applications for pressure, strain, temperature, humidity, biochemical, gas, and so on is then reviewed and compared. For emerging applications from many Internet of Things scenarios, geometrical constraints, such as small and non-invasive coils, reduce the magnetic coupling between the sensor and the readout coil, resulting in a limited interrogation distance. Furthermore, an increasing number of applications also require the simultaneous measurement of multiple parameters. Recent efforts to increase the interrogation distance and to extend the measurement of single parameter to multiple parameters are finally outlined. [2016-0093]

LC Passive Wireless Sensors Toward a Wireless Sensing Platform: Status, Prospects, and Challenges

https://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=1243&context=ameslab_manuscripts

Review of Fe-6.5 wt%Si high silicon steel—A promising soft magnetic material for sub-kHz application

This paper proposes a fully embedded resonant pressure sensor operating in the MHz range and realized in the standard low-temperature co-fired ceramics (LTCC) technology. Buried sensor design and usage of LTCC materials enable application of this sensor in high-temperature and chemically aggressive environments. Upgraded sensor and sensor-antenna models residing on an analytical concept are used for prediction of the system performance. Also, simulation results show that an increase of Young's modulus for the LTCC tape diminishes the sensor sensitivity. An experimental setup for wireless data retrieval is designed enabling precise measurement of the influence of pressure variation on the sensors resonant frequency. Experimentally attained results are compared with electrical characteristics determined by analytical calculations as well as those derived from electrical simulations.

A Wireless Embedded Resonant Pressure Sensor Fabricated in the Standard LTCC Technology

This paper describes the design and fabrication of low-cost coplanar waveguide (CPW) miniature meander inductors. Inductors are fabricated on a flexible plastic polyimide foil in ink-jet printed technology with silver nanoparticle ink in a single layer. For the first time, the detailed characterization and simulation of CPW inductors in this technology is reported. The inductors are developed with impressive measured self-resonance frequency up to 18.6 GHz. The 2.107-nH inductor measures only 1 mm × 1.7 mm × 0.075 mm and demonstrates a high level of miniaturization in ink-jet printing technology. The measured response characteristics are in excellent agreement with the predicted simulation response.

Low-Cost CPW Meander Inductors Utilizing Ink-Jet Printing on Flexible Substrate for High-Frequency Applications

In this paper design, modeling and characterization of single and double coils, which consist of conductive layer embedded in the soft ferrite material, are described. These surface-mount components, comprising of a cofired multilayered ferrite and coil, have been developed in the ceramic coprocessing technology. A simple analytical model of proposed structures is presented. This model is very suitable for circuit simulations and for prediction of frequency characteristics of considered inductors. The inductance and impedance of coils embedded in low permeability or high permeability ferrite material are calculated and compared. Also, these suppressors were experimentally tested in the frequency range 1 MHz-3 GHz using an Agilent 4287 A RF LCR meter. The calculated results were in good agreement with the measured ones.

Analysis, design, and characterization of ferrite EMI suppressors

The quality of modeling and analyzing of RF IC with planar inductors extremely depends on accuracy of expression for inductance. In this paper efficient methods for total inductance calculation of meander inductor are given. By using proposed algorithm, we are able to predict correctly all inductance variations introduced by varying geometry parameters. Our. developed program gives possibility for fast and accurate inductance calculation for meander inductor, while new expression in monomial form is useful for optimization of this inductor. The results validations, given by proposed software tool are conformed by comparison with measured data from literature.

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Compact Form of Expressions for Inductance Calculation of Meander Inductors

This paper presents a meander-type displacement inductive sensor, usable for the detection of small displacements (less than 0.5 mm) in the plane. It also describes design, realization, and the input inductance measurement of sensor. A displacement in two directions can be detected by using two sensor elements, each having a pair of meander coils. In each pair, one of the coils is fixed and between its terminals the input inductance was measured, while the other coil is short-circuited. If one coil is moved above the other, in directions of x - and z -axes, coupling between the coils will change, as well as the input inductance, which serves as a measure of displacement. In order to achieve better linearity of the sensor, longitudinal gaps are inserted in the middle of each conductive segment of one fixed coil. Four sets of inductive sensors were realized: without gap and with three different gaps. Planar, low-cost PCB technology was chosen for our prototype. In addition, an improved model of the inductive sensor is proposed. The input inductance of displacement sensor was calculated and compared with measured values. A good agreement was found.

Ljiljana Zivanov

Papers

A Wireless Embedded Resonant Pressure Sensor Fabricated in the Standard LTCC Technology

Low-Cost CPW Meander Inductors Utilizing Ink-Jet Printing on Flexible Substrate for High-Frequency Applications

Analysis, design, and characterization of ferrite EMI suppressors

Compact Form of Expressions for Inductance Calculation of Meander Inductors

A Novel Approach to Extending the Linearity Range of Displacement Inductive Sensor