Recent years have seen the development of spintronic devices and their applications in biomedical areas. Spintronic devices rely on detecting or manipulating a magnetic field, a field to which biological matter is relatively transparent. The recent use of spintronic devices in biomedical areas has included diagnosing diseases such as cancer and cirrhosis, genotyping DNA, point-of-care devices, and flexible electronics. Up to date, most of the spintronic devices in biomedical applications fall into three mainstream types: anisotropic, giant, and tunneling magnetoresistance devices. Each of these has its advantages and drawbacks, which this review explores and discusses. The advent of spintronics gives us a new low-power, low-cost, ease-of-manufacture alternative to standard CMOS sensors. The sensitivity of spintronic biosensors has been progressing steadily, expected to increase tremendously in the next few years.

In this paper, we introduce a novel design of a metamaterial unit cell absorber, which is based on a metal/insulator/metal sandwich structure. The design is subjected to comprehensive finite element method (FEM) computational analysis to ensure accurate and reliable results. The proposed metamaterial sandwich structure demonstrates exceptional absorption performance, achieving a nearly perfect absorption rate of 99.996% at the resonance infrared frequency of 39.8 THz. To provide a detailed theoretical explanation of nearly perfect absorption, we employ the effective medium theory, impedance matching, and field distribution analysis. Additionally, we have optimized the structural parameters of the sensor to maximize its absorption peak. This includes optimizing the thickness of the gold (Au) layer (from 0.03 to 0.28 μm), the distance between the L shape corners (from 0.60 to 0.90 μm), and the thickness of SiC dielectric spacer (from 0.20 to 0.45 μm). Furthermore, we showcase the remarkable sensitivity of the proposed metamaterial unit cell in detecting subtle changes in the refractive index through the implementation of a sensing medium setup in our model. Remarkably, we achieve a frequency shift sensitivity of 3.74 THz/RIU, along with a quality factor (Q-factor) of 10.33, for a wide range of refractive indices (1.0 - 2.0). Moreover, for cancer detection, we attain a sensitivity of 3.5 THz/RIU. These findings highlight the exceptional performance of our approach in accurately detecting changes in refractive index, making it a promising candidate for various sensing applications. The novelty of our work lies in the design of a metamaterial unit cell structure. This configuration exhibits several noteworthy features, including wide incident angle (θ) coverage up to 60o, polarization insensitivity, exceptional frequency shift sensitivity, high absorption peaks across a wide range of refractive indices, and the ability to distinguish cancer cells from healthy ones.

Since its first report in 2006, magnetic particle spectroscopy (MPS)-based biosensors have flourished over the past decade. Currently, MPS are used for a wide range of applications, such as disease diagnosis, foodborne pathogen detection, etc. In this work, different MPS platforms, such as dual-frequency and mono-frequency driving field designs, were reviewed. MPS combined with multi-functional magnetic nanoparticles (MNPs) have been extensively reported as a versatile platform for the detection of a long list of biomarkers. The surface-functionalized MNPs serve as nanoprobes that specifically bind and label target analytes from liquid samples. Herein, an analysis of the theories and mechanisms that underlie different MPS platforms, which enable the implementation of bioassays based on either volume or surface, was carried out. Furthermore, this review draws attention to some significant MPS platform applications in the biomedical and biological fields. In recent years, different kinds of MPS point-of-care (POC) devices have been reported independently by several groups in the world. Due to the high detection sensitivity, simple assay procedures and low cost per run, the MPS POC devices are expected to become more widespread in the future. In addition, the growth of telemedicine and remote monitoring has created a greater demand for POC devices, as patients are able to receive health assessments and obtain results from the comfort of their own homes. At the end of this review, we comment on the opportunities and challenges for POC devices as well as MPS devices regarding the intensely growing demand for rapid, affordable, high-sensitivity and user-friendly devices.

Flexible magnetic field nanosensors hold immense potential for wearable electronics, offering a range of advantages such as comfort, real-time health monitoring, motion sensing, durability, and seamless integration with other sensors. They are expected to revolutionize wearable technologies and drive innovation in various domains, enhancing the overall user experience. In this review, we provide an overview of recent advances in flexible magnetic field nanosensors, including flexible Hall sensors, flexible magnetoresistive (MR) sensors such as giant magnetoresistance (GMR), magnetic tunnel junction (MTJ), and anisotropic magnetoresistance (AMR) sensors, flexible fluxgate sensors, and flexible giant magnetoimpedance (GMI) sensors. We discuss different fabrication methods and real-life applications for each type of sensor as well as the technical challenges faced by these sensors. The use of these flexible nanosensors opens more possibilities for human−computer interaction and presents exciting opportunities for wearable technology in diverse fields. The robustness of these sensors along with the trend to reduce energy consumption will continue to be important research areas. Future trends in flexible magnetic field nanosensors include energy harvesting from the body, miniaturization and lower power consumption, improved durability and reliability, and reduced cost. These advancements have the potential to drive the widespread adoption of flexible magnetic field nanosensors in wearable devices, enabling innovative applications and enhancing the overall user experience.

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