Anapole-enabled RFID security against far-field attacks

Radio frequency identification (RFID) is a widely used wireless technology for contactless data exchange. Owing to international standardization and one-way security nature of the communication protocol, RFID tags, holding sensitive information, may be a subject to theft. One of the major security loopholes is the so-called far-field attack, where unauthorized interrogation is performed from a distance, bypassing the user’s verification. This loophole is a penalty of using a dipole-like RFID tag antenna, leaking wireless information to the far-field. Here we introduce a new concept of anapole-enabled security, prohibiting far-field attacks by utilizing fundamental laws of physics. Our design is based on radiationless electromagnetic states (anapoles), which have high near-field concentration and theoretically nulling far-field scattering. The first property enables performing data readout from several centimeters (near-field), while the second prevents attacks from a distance, regardless an eavesdropper’s radiated power and antenna gain. Our realization is based on a compact 3 cm high-index ceramic core–shell structure, functionalized with a thin metal wire and an integrated circuit to control the tag. Switching scheme was designed to provide a modulation between two radiation-less anapole states, blocking both up and down links for a far-field access. The anapole tag demonstrates more than 20 dB suppression of far-field interrogation distance in respect with a standard commercial tag, while keeping the near-field performance at the same level. The proposed concept might significantly enhance the RFID communication channel in cases, where information security prevails over cost constrains.

Intermetallic Coating Using a 3-Dimensional Micro Welder

The authors have studied a new method of intermetallic coating using a small TIG welder. This method is based on a reaction between small liquid beads produced from very thin metal wire and the substrate metal surface. The authors designed a computer-aided 3-dimensional micro welder (3DMW) for a previous study on freeform fabrication of intermetallics, and have applied it to this study on intermetallic coating. In this study, a predetermined length of thin aluminum wire was fed onto the titanium substrate surface, and a spark was stricken from a thin electrode of a W-Ce2O3 alloy to make a small aluminum liquid bead on the titanium substrate surface and to simultaneously melt a small area of the substrate surface beneath the liquid bead. All process conditions had been programmed beforehand, including the length of the wire feeding per spark, the position of the electrode, electric power, movement of the stage holding the substrate, etc. The liquid bead containing aluminum and titanium rapidly solidified on the titanium substrate surface producing titanium aluminides on it. Repetition of the aluminum wire feeding, the electrode positioning and the spark striking produced a coating layer consisting of sub-layers of TiAl3, TiAl and Ti3Al from the surface side to the substrate side. Vickers hardness and wear resistance of the coated sample were remarkably improved.

Development of Freeform Fabrication of Metals by Three Diminsional Micro-Welding

A newly developed freeform fabrication process named 3D Micro-Welding, which is a combined system of a micro-TIG welding and a layered manufacturing method, is demonstrated. Various refractory alloys such as Inconel, stainless steel, and Invar can be freeformed besides elemental metals like titanium. Small metal beads of ~1mm in diameter are formed by emitting micro arc to the top of a thin metal wire of 0.2mm diameter. A fused bead is welded to a metal substrate or previously formed beads. By continuing this process and building up beads layer by layer under the control of CAD/CAM system, 3D objects were produced. In this study, optimization of micro-welding parameters such as the waveform of pulsed arc current and electrode materials were investigated and simple 3D objects of Inconel 600, SUS 304, Invar 42 were formed. The interfaces between adjacent beads were joined well and no crack or pore existed in the formed objects. The density and Vickers hardness of Inconel 600 objects showed comparable values to the commercial Inconel alloy, however the yield strength and Young’s modulus was about 80% and 70% of that alloy, respectively.

Artificial Plasmonic Metamaterial Fabricated by Micro-Stereolithography

Micro-structured materials, which contain engineered subwavelength components, can be designed to have positive or negative ε and μ at desired frequency. In this paper, we demonstrate a high pass Terahertz (THz) filter which utilizes the lowered plasma frequency of thin metal wire structures. This high pass filter may have applications in the THz imaging systems. The filter is formed by two-dimensional cubic lattice of thin metal wires. The diameter of the wire is 30 μm, the lattice constant is 120 μm, and the length of the wire is 1mm. Micro-stereolithography technique is applied to fabricate this high aspect ratio cylinders. The reflection property of the filter is characterized by Fourier transform infrared (FTIR) spectroscopy, and a plasma frequency at 0.7 THz is observed, which agrees with the approximate theory.

Failure Estimation of Semiconductor Chip During Wire Bonding Process

Wire bonding, a process of the connection between a semiconductor chip and a lead frame by a thin metal wire, is one of the important processes of electronic packaging. This paper presents failure estimation of a silicon chip and a GaAS chip during a gold wire bonding process. The gold wire bonding process is carried out by pressing a gold ball made at a tip of the gold wire on a semiconductor chip and vibrating it by ultrasonic. High contact pressure is useful for shortening the process cycle, but it sometimes causes failure of the semiconductor chip. Elastic-plastic large deformation contact analyses are performed and the distributions of the stresses in these semiconductor chips are investigated. The possibility of failure of a semiconductor chip under usual wire bonding pressure is pointed out only for a GaAs chip.