Philip W. T. Pong

A Polyferroplatinyne Precursor for the Rapid Fabrication of L1 0 -FePt-type Bit Patterned Media by Nanoimprint Lithography

A polyferroplatinyne polymer can be patterned on the surface of Si wafer in ordered nanoline or nanodot shapes with PDMS molds through nanoimprint lithography (NIL), and subsequent thermal treatment gives rise to the nanopatterned arrays of L1(0) -FePt nanoparticles with the same periodicities. The method offers excellent potential to be utilized in the simple and rapid fabrication of bit patterned media for magnetic data recording.

Liver cancer immunoassay with magnetic nanoparticles and MgO-based magnetic tunnel junction sensors

We have demonstrated the detection of alpha-fetoprotein (AFP) labeled with magnetic nanoparticles (MNPs) using MgO-based magnetic tunnel junction (MTJ) sensors. AFP is an important hepatic tumor biomarker and the detection of AFP has significant applications for clinical diagnostics and immunoassay for early-stage liver cancer indications. In this work, MgO-based MTJ sensors and 20-nm iron-oxide magnetic nanoparticles (MNPs) were used for detecting AFP antigens by a sandwich-assay configuration. The MTJ sensors with a sensing area of 4 × 2 μm2 possess tunneling magnetoresistance (TMR) of 122% and sensitivity of 0.95%/Oe at room temperature. The target AFP antigens of three concentrations were successfully detected, and the experimental data indicate that the resistance variations of the MTJ sensor increased with the AFP concentration ratios proportionally. These results demonstrate that MgO-based MTJ sensors together with MNPs are a promising biosensing platform for liver cancer immunoassay.

Review of Noise Sources in Magnetic Tunnel Junction Sensors

Noise problem limits the sensitivity of magnetic tunnel junction (MTJ) sensors for ultra-low magnetic field applications. Noise analysis not only helps in finding ways to eliminate noise disturbances but also essential for understanding the electronic and magnetic properties of MTJs. These approaches provide insight for optimizing the design of MTJ sensors before fabrication. This paper reviews the noise sources in MTJ sensors reported in recent years. Both the origins and mathematical derivations of the noise sources are presented, illustrating how different factors affecting the performance of MTJ sensors. A brief outlook of challenges in the future is also given.

On Wireless Sensors Communication for Overhead Transmission Line Monitoring in Power Delivery Systems

The transmission of energy is monitored in the smart grid through deploying sensors in all the components, including the overhead transmission lines. There are many poles/towers supporting a long overhead transmission line. Naturally, sensors are deployed on the location close to the poles/towers on each span. Due to the limited transmission range of the wireless transceiver module of a sensor, researchers generally assume that data generated by a sensor have to be delivered to the substation through a set of sensors in-between. This results in a linear network model. In this paper, we first analyze the performance of this model in handling the traffics extracted from an existing testbed. We realize that the linear network model may not be sufficient to support future smart grid applications which may have diversified requirements on data delivery. We then study a new network model in which sensor/relay nodes can also communicate with other nodes using a wide area network such as the cellular network. In this new model, the network formed can be reconfigured based on the application requirements to deliver information to the substations efficiently and effectively.

Investigation of pyrolysis temperature in the one-step synthesis of L10 FePt nanoparticles from a FePt-containing metallopolymer

Ferromagnetic (L10 phase) FePt alloy nanoparticles (NPs) with extremely high magnetocrystalline anisotropy are considered to be very promising candidates for the next generation of ultrahigh-density data storage systems. The question of how to generate L10 FePt NPs with high coercivity, controllable size, and a narrow size distribution is a challenge. We report here a single-step fabrication of L10 FePt NPs by employing one of the two new polyferroplatinyne bimetallic polymers as precursors. The influence of the pyrolysis temperature on the size and magnetic properties of the resulting FePt alloy NPs has been investigated in detail.

Efficient Communication of Sensors Monitoring Overhead Transmission Lines

It is foreseen that a future smart grid has to handle more dynamic and distributed electricity supply and consumption. In that case, a robust automation system becomes essential. To monitor the status of the power system, a large amount of sensors are deployed in both the transmission grid and distribution grid. The sensors generate massive amount of data periodically for automation. This paper studies how the data measured on transmission lines can be delivered efficiently to substations. It has been demonstrated that the traditional way of data transmission is not sufficient and direct wireless links should be used to reduce the delay in information delivery. Furthermore, optimal placement of these direct wireless links is studied aiming at minimizing the delay in information delivery. The associated energy consumption in data transmission is also investigated.

Magnetics in Smart Grid

A revolution in power transmission and distribution, driven by environmental and economic considerations, is occurring all over the world. This revolution is spearheaded by the development of the smart grid. The smart grid is bringing profound change to both the power systems and many related industries. This paper reviews the development of the smart grid and its correlation with magnetics, including electromagnetic compatibility issue, magnetic-field-based measurement/monitoring, and magnetic energy storage/conversion. The challenge to the field of magnetics and the usage of the cutting edge magnetics technology in the development of the smart grid are discussed. This paper enables researchers in the magnetics community to be acquainted with the progress in the smart grid and inspires innovative applications of state-of-the-art magnetics technologies in the smart grid.

A Novel Approach for Fault Location of Overhead Transmission Line With Noncontact Magnetic-Field Measurement

Prompt and accurate location of faults in a large-scale transmission system can accelerate system restoration, reduce outage time, and improve system reliability. Traditional approaches are categorized into traveling-wave-based and impedance-based measurement techniques. The traveling-wave-based approach requires detection devices to connect to the high-voltage transmission line, making the solution complex and costly. And the impedance-measurement-based approach is highly dependent on the quality of the signal and affected by fault resistance, ground resistance and non-homogeneity in line configuration. Hence, these approaches may cause a location error that is unacceptable in certain operation cases. In this paper, a novel approach based on noncontact magnetic-field measurement is proposed. With the magnetic field measured along the transmission line by using highly sensitive, broadband, and a low-cost magnetoresistive magnetic sensor, the fault span can be located. The collected data can be further used for identifying the fault type and location within the fault span. The overall system was designed and numerical simulations were performed on typical tower configurations. The simulated results verify the validity of the proposed scheme.

Novel Application of Magnetoresistive Sensors for High-Voltage Transmission-Line Monitoring

High-voltage transmission lines are responsible for transmission of electric power. Their sag and electric current are important parameters for transmission-line monitoring. In this paper, a simple and promising method based on magnetoresistive sensors is proposed for transmission-line monitoring. This is a noncontact method and its installation is simple without the need for power cut. The method involves measuring emanated magnetic field from a line conductor at the ground level and, then, calculating the source position and current inversely. A proof-of-concept laboratory setup was constructed and a series of experiments were carried out for demonstration. This method can handle complicated transmission-line configuration by integrating the stochastic optimization approach into the inverse electromagnetic calculation. It was tested with the computational simulation of a 500 kV transmission-line configuration. The result shows the feasibility of using this transmission-line monitoring method in reality.

Design of superparamagnetic nanoparticles for magnetic particle imaging (MPI).

Magnetic particle imaging (MPI) is a promising medical imaging technique producing quantitative images of the distribution of tracer materials (superparamagnetic nanoparticles) without interference from the anatomical background of the imaging objects (either phantoms or lab animals). Theoretically, the MPI platform can image with relatively high temporal and spatial resolution and sensitivity. In practice, the quality of the MPI images hinges on both the applied magnetic field and the properties of the tracer nanoparticles. Langevin theory can model the performance of superparamagnetic nanoparticles and predict the crucial influence of nanoparticle core size on the MPI signal. In addition, the core size distribution, anisotropy of the magnetic core and surface modification of the superparamagnetic nanoparticles also determine the spatial resolution and sensitivity of the MPI images. As a result, through rational design of superparamagnetic nanoparticles, the performance of MPI could be effectively optimized. In this review, the performance of superparamagnetic nanoparticles in MPI is investigated. Rational synthesis and modification of superparamagnetic nanoparticles are discussed and summarized. The potential medical application areas for MPI, including cardiovascular system, oncology, stem cell tracking and immune related imaging are also analyzed and forecasted.