High dielectric constant and low dielectric loss are desirable electrical properties for next-generation polymer dielectrics that show promise for applications in pulsed power, power electronics, and printable electronics. Unfortunately, the dielectric constant of polymers is often limited to 2–5, much lower than that of inorganic dielectrics, because of the nature of hydrocarbon covalent bonds for electronic and atomic polarizations. It is essential to understand the fundamental physics of different types of polarization and the associated loss mechanisms in polymers. In this Perspective, we discuss the characteristics of each polarization and explain how to enhance the polarization using rational molecular designs without causing significant dielectric losses. Among various approaches for high dielectric constant and low loss polymers, the multilayer film technology is of particular interest because a multilayer film is a unique one-dimensional system with tailored material choices, layer thicknesses, a...

50th Anniversary Perspective: Dielectric Phenomena in Polymers and Multilayered Dielectric Films

The effect of particle size, charge, and composition on the loading characteristics of an electrically active fibrous filter material

Electrically active fibrous filters, that is fibrous filters whose fibers carry a permanent electric charge, are a popular alternative to conventional fibrous filters in applications where low pressure drop and high collection efficiencies are critical. The advantage of these materials is the additional collection efficiency, due to electrostatic mechanisms, that can be achieved without pressure drop increase. Although the efficiency of these materials is always superior to that of a conventional material of similar structure, the efficiency of these materials can fall as they are loaded with particles, so it is necessary that a proper account be taken of this process during use. Significant advances have been made in understanding the mechanisms responsible for this reduction in efficiency in a recent experimental study of the loading behavior of a mixed fiber type electrically active material. This study has identified a number of parameters that cause the filtration efficiency to be reduced, a...

Parameters Affecting the Loading Behavior and Degradation of Electrically Active Filter Materials

Importance Smoke generated during surgical procedures has long been thought to be hazardous to hospital personnel; however, the degree of danger has yet to be determined. Observations The dangers of surgical smoke are associated with the composition of the plume. Small-particulate matter is found in the smoke that is easily inhaled. Particulates deposit in the lungs, circulatory system, and other organs, which may cause numerous health problems. The smoke also contains many gaseous compounds known to cause cancer. The type of tissue and the form of cautery have been shown to alter the composition of the surgical smoke. Well-cited articles have asserted that daily inhaled surgical smoke could be equivalent to smoking dozens of cigarettes. Unsafe levels of cancer-causing compounds have been found in the smoke. However, there is no firm evidence that operating room personnel show increased cancer rates compared with the general population. Data implicating other forms of passively inhaled smoke, such as fumes associated with cooking and wood burning, are likely comparable to the smoke issued during surgical procedures. Most operating rooms do not require smoke evacuation, and the elimination techniques are variable. Most systems rely on dispersion and, possibly, mechanical evacuation and filtration. Newer electric filters show promise but require more development. Conclusions and Relevance Surgical smoke is dangerous, but the severity of the risk has yet to be determined. Therefore, no safe level is known at this point. Efforts should be made to reduce and possibly eliminate smoke from the operating room. Research into cost-effective forms of smoke evacuation is necessary. Studies of respiratory and cancer sequelae of exposure to operating room smoke in personnel who have had long-term exposure to surgical smoke is also needed.

https://jamanetwork.com/journals/jamasurgery/articlepdf/2748067/jamasurgery_limchantra_2019_rv_190004.pdf

Surgical Smoke Exposure in Operating Room Personnel: A Review

The collection performance of electret filters in the particle size range 10 nm-10 μm

A new type of air filter in which the dust particles are captured very effectively by electrostatic forces is presented. This is accomplished by making the filter from polymer fibers that carry a permanent positive and negative charge. A method is outlined for producing such filters on a large scale and results are given of tests in which the filters are challenged with various aerosols. The advantage of the new filters is that they combine a high capturing efficiency with a low resistance to air flow. Among the numerous applications, personal protective face masks for people working in dusty environments are especially valuable.

Leonard M. Van Rossen

Papers

Electret Filters for High-Efficiency and High-Flow Air Cleaning

Electret Filters forHigh-Efficiency andHigh-Flow AirCleaning