According to Edholm’s law, the demand for point-to-point bandwidth in wireless short-range communications has doubled every 18 months over the last 25 years. It can be predicted that data rates of around 5–10 Gb/s will be required in ten years. In order to achieve 10 Gb/s data rates, the carrier frequencies need to be increased beyond 100 GHz. Over the past ten years, several groups have considered the prospects of using sub-terahertz (THz) and THz waves (100–2000 GHz) as a means to transmit data wirelessly. Some of the reported advantages of THz communications links are inherently higher bandwidth compared to millimeter wave links, less susceptibility to scintillation effects than infrared wireless links, and the ability to use THz links for secure communications. Our goal of this paper is to provide a comprehensive review of wireless sub-THz and THz communications.

Electrospinning has become a widely implemented technique for the generation of nonwoven mats that are useful in tissue engineering and filter applications. The overriding factor that has contributed to the popularity of this method is the ease with which fibers with submicron diameters can be produced. Fibers on that size scale are comparable to protein filaments that are observed in the extracellular matrix. The apparatus and procedures for conducting electrospinning experiments are ostensibly simple. While it is rarely reported in the literature on this topic, any experience with this method of fiber spinning reveals substantial ambiguities in how the process can be controlled to generate reproducible results. The simplicity of the procedure belies the complexity of the physical processes that determine the electrospinning process dynamics. In this article, three process domains and the physical domain of charge interaction are identified as important in electrospinning: (a) creation of charge carriers, (b) charge transport, (c) residual charge. The initial event that enables electrospinning is the generation of region of excess charge in the fluid that is to be electrospun. The electrostatic forces that develop on this region of charged fluid in the presence of a high potential result in the ejection of a fluid jet that solidifies into the resulting fiber. The transport of charge from the charge solution to the grounded collection device produces some of the current which is observed. That transport can occur by the fluid jet and through the atmosphere surrounding the electrospinning apparatus. Charges that are created in the fluid that are not dissipated remain in the solidified fiber as residual charges. The physics of each of these domains in the electrospinning process is summarized in terms of the current understanding, and possible sources of ambiguity in the implementation of this technique are indicated. Directions for future research to further articulate the behavior of the electrospinning process are suggested.

We compare the use of free-space electro-optic sampling (FSEOS) with photoconducting antennas to detect terahertz (THz) radiation in the range of 0.1–3 THz. For the same average THz power and low-frequency modulation, signal-to-noise ratio and sensitivity are better with antenna detection at frequencies smaller than 3 THz. When the modulation frequency is increased to more than 1 MHz in FSEOS, both detection schemes have comparable performance. Using a singular-electric-field THz emitter, we demonstrate the feasibility of a THz imaging system using real-time delay scanning in FSEOS and only 20 mW of laser power.

We present new designs of more efficient terahertz (THz) radiation emitters and detectors enhanced by electric field singularities using sharp and laterally offset electrodes. We compare the performances of the terahertz emission and different polarization properties resulting from these structures. An average THz radiation power of 3 μW is achieved under 20 mW excitation, calibrated by free space electro-optic sampling. We also study the gap size dependence of the THz radiation, and find an absence of a positive electrode effect in the small gap limit.