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Lyon, France

Kahouli A.,Joseph Fourier University | Kahouli A.,Laboratory for Materials | Sylvestre A.,Joseph Fourier University | Jomni F.,Laboratory for Materials | And 2 more authors.
Applied Physics A: Materials Science and Processing | Year: 2012

45% semi-crystalline parylene-C (-H 2C-C 6H 3Cl-CH 2-) n thin films (5.8 μm) polymers have been investigated by broadband dielectric spectroscopy for temperatures above the glass transition (T g =90°C). Good insulating properties of parylene-C were obtained until operating temperatures as high as 200°C. Thus, low-frequency conductivities from 10 -15 to 10 -12 S/cm were obtained for temperatures varying from 90 to 185°C, respectively. This conductivity is at the origin of a significant increase in the dielectric constant at low frequency and at high temperature. As a consequence, Maxwell-Wagner-Sillars (MWS) polarization at the amorphous/crystalline interfaces is put in evidence with activation energy of 1.5 eV. Coupled TGA (Thermogravimetric analysis) and DTA (differential thermal analysis) revealed that the material is stable up to 400°C. This is particularly interesting to integrate this material for new applications as organic field effect transistors (OFETs). Electric conductivity measured at temperatures up to 200°C obeys to the well-known Jonscher law. The plateau observed in the low frequency part of this conductivity is temperature-dependent and follows Arrhenius behavior with activation energy of 0.97 eV (deep traps). © 2011 Springer-Verlag. Source


Kahouli A.,Joseph Fourier University | Kahouli A.,Tunis el Manar University | Jomni F.,Tunis el Manar University | Sylvestre A.,Joseph Fourier University | And 2 more authors.
Journal of Physics D: Applied Physics | Year: 2011

Measurements under both transient and steady-state conditions on parylene C (H 2CC 6H 3ClCH 2) n, also called PPX C, were made for different electric fields ranging from 8.33 to 33.33MVm 1. The transient current behaviour is hyperbolic in nature up to 125°C. Above, the current is transient free and becomes constant reflecting the presence of the steady state. The decay rate of the transient current increases with increasing temperature and field. The transient current is attributed mainly to the dipolar relaxation due to the polarization of the CCl dipole. The J1/T characteristic reflects the change in the conduction regime occurring at a critical temperature associated with the glass transition temperature of the materials. The JE measurements show that hopping conduction is the possible mechanism below and above T g of parylene C. The activation energy is determined to be 0.13eV, independent of the electric fields below T g and varies from 0.65 to 0.94eV above T g, indicating the presence of more than one type of trapping centres in parylene C. The ionic jump distance a is estimated to be 5.606.68 below T g and 8.3626.58 above T g. © 2011 IOP Publishing Ltd. Source


Schultz A.,University of Cincinnati | Chevalliot S.,University of Cincinnati | Chevalliot S.,Varioptic | Kuiper S.,Optilux Inc. | Heikenfeld J.,University of Cincinnati
Thin Solid Films | Year: 2013

Low-voltage electrowetting requires a thin dielectric capacitor and field strengths approaching 1 MV/cm. Unlike traditional metal/dielectric/metal capacitors, the conducting electrowetted liquid can electrically propagate through the smallest dielectric defects or pores, even for the best barrier polymers such as Parylenes, leading to catastrophic failure such as electrolysis. A detailed analysis of double layer dielectric systems is shown to provide > 100 times reduction in defect density, with > 10 cm2 area exhibiting no dielectric failure at > 2 times the required electrowetting voltage. An anodized-Al2O3/Parylene-HT stack provides electrowetting contact angle modulation down to saturation at 70 at < 15 V with breakdown protection to > 3 times that voltage. These results build on previous findings on the effect of ion type, liquid type, polymer dielectric choice, electrode material, and provide a next major advance in electrowetting reliability. © 2013 Elsevier B.V. Source


News Article | June 25, 2008
Site: techcrunch.com

For the “extremely small camera” sector, this could be a real boon. These liquid lenses are fixed in place within the camera, manipulated using electricity, and — well, I’ll let Varioptic explain it: It works much like the human eye, using electricity to alter the shape of two drops of liquid, to bend light, alter focus, and produce a miniature, yet powerful (multi-megapixel) lens for a variety of applications Yes, that sounds exactly like the human eye. But joking aside, this is a really cool idea and considering the continual need to shrink lenses and how crappy most tiny fixed lenses are, it may actually find some real traction. That they can make it work in a fast autofocus situation like a webcam is promising. It always takes some doing to displace a product on the market (especially one with as much inertia as the glass lens) but it’s always worthwhile to try. I hope I get to see one of these little things perform soon.


News Article | June 9, 2011
Site: www.cnet.com

In 2004, we covered Varioptic's liquid lens technology, reporting that by 2005 consumers could expect to see liquid lens cameraphones on store shelves. It's 2011, and we still don't have those products. But we're getting closer. As a refresher, liquid lenses use two liquids--a refractive liquid (an oil), and a conductive, non-refractive liquid--together in a tiny sandwich, with the conductive liquid touching tiny electrodes. A current is applied to the electrodes to pull the liquid to them, and surface tension between the liquids changes the shape of the refractive material, and thus the optical characteristics of the lens package. Simple liquid lenses have variable focal length, so they can focus. If you put four electrodes around the circumference of the lens, you can also change the axis of the lens, enabling image stabilization. The liquid lenses are faster to focus than current-tech voice-coil focusing lenses, and they take a fraction of the power, too. To make a liquid lens zoomable, you need a stack of three liquid lens components; that's in development. The technology is proven, and has been in industrial and security products for years, but the big manufacturer of liquid lenses, Varioptic, doesn't have the manufacturing capacity to turn out hundreds of millions of components required for the consumer cameraphone. In 2010, a new CEO of Varioptic, Hamid Farzaneh, sold the company to Parrot and spun out a new liquid lens company, Optilux, to focus on the consumer market. Optilux is an American company; Varioptic and Parrot are both French. Farzaneh has an exclusive license to use the Varioptic technology in consumer products, and funding to develop a manufacturing process to scale up to consumer product run-rates (Varioptic can ship about 100,000 lenses a month, a far cry from the millions that Farzaneh thinks the market will want). That's what he came in to talk to me about this week. He's hoping to set up both R&D and manufacturing in the U.S. Over time, as the new company digs into the consumer market, Optilux technology will diverge from Varioptic. Farzaneh said that having manufacturing next door to U.S. engineers will keep development moving faster. It also increases the control the company can maintain of its intellectual property. Finally, he says, he needs an automated system for high-volume production, and automated plants are easier to set up next to U.S.-based engineers, compared with the current liquid lens construction techniques, which are based on hand-assembled lenses that benefit from lower (overseas) labor costs. The timing of all this: We should, Farzaneh says, finally start seeing Optilux liquid lenses in cameras in 2013. These will be the auto-focusing and image-stabilized lenses. The zoom packages could show up in consumer products in 2014.

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