2008 NOV 24 - (VerticalNews.com) -- "Recently, micro power generation using electrets has attracted much attention due to its large power output at a low frequency range. Since the theoretical power output is proportional to the square of the surface charge density of the electret, the development of a high-performance electret is required," scientists in Kanagawa, Japan report.

  "In the present study, it is shown that the surface charge density of a CYTOP electret is significantly improved by the addition of terminal groups. Based on this fact, a novel high-performance polymer electret has been developed by doping a silane-coupling reagent into the polymer. A series of measurements of surface potential and TSD ( thermally stimulated discharge) spectra was made for various CYTOP films prepared with different silane-coupling reagent concentrations. It is found that the surface charge density, charge stability and thermal resistibility of electric charges are markedly improved by the doping. A surface charge density of 1.5 mC cm(-2), which is three times larger than that of Teflon AF, has been obtained on a 15 mu m thick film. In addition, the thermal stability of the CYTOP electret is superior to that of Teflon AF. Power generation experiment is also performed using the patterned CYTOP electret of 20 x 20 mm(2)," wrote Y. Sakane and colleagues, Asahi Glass Co., Ltd. ...read more

  2008 NOV 24 - (VerticalNews.com) -- According to a study from Rome, Italy, "A new micro-molding machine is described which is used to fabricate micro-parts made of a thermoplastic material. A single pellet is directly molded into a transparent mold by means of a diode laser source."

  "A very low holding pressure is applied and no mold heating system is required; therefore the size of the micro-machine is extremely small as well as the size of the mold. The micro-machine was used to mold three different materials: high-density polyethylene (HDPE), polystyrene (PS) and acrylonitrile-butadiene-styrene (ABS). A process map was initially defined for all the materials by changing the main process variables (i.e. laser power, molding time and focalization condition). In this phase, small disks, 3.5 mm in diameter, were molded and their diameter was measured to evaluate the dimensional accuracy of the process," wrote F. Quadrini and colleagues, Tor Vergata University ...read more

  2008 NOV 24 - (VerticalNews.com) -- According to a study from the United States, "An electret power generator is developed using a new electret made of a charged parylene HT (R) thin-film polymer. Here, parylene HT (R) is a room-temperature chemical-vapor-deposited thin-film polymer that is MEMS and CMOS compatible."

  "With corona charge implantation, the surface charge density of parylene HT (R) is measured as high as 3.69 mC m(-2). Moreover, it is found that, with annealing at 400. C for 1 h before charge implantation, both the long-term stability and the high-temperature reliability of the electret are improved. For the generator, a new design of the stator/rotor is also developed. The new micro electret generator does not require any sophisticated gap-controlling structure such as tethers. With the conformal coating capability of parylene HT (R), it is also feasible to have the electret on the rotors, which is made of either a piece of metal or an insulator. The maximum power output, 17.98 mu W, is obtained at 50 Hz with an external load of 80 M Omega," wrote H.W. Lo and colleagues, California Institute of Technology ...read more