Parylene HT is a good insulator with low dissipation factor (D = 0.0002 at 60 Hz and D = 0.002 at 1 kHz), with a surface energy of about 31 mN/m + 1 mN/m, and has a low polar surface energy component (< 2 mN/m).
Parylene HT films presenting a thickness d comprised between about 0.5 μm and about 10 μm, have a relative dielectric constant εr ranging from about 2.2 to about 2.4
Parylene HT is a transparent polymer in visible wavelength, and may advantageously be used also as hydrophobic layer coated on the window of an optical electrowetting device, especially an optical lens driven by electrowetting.
Considering optical properties of Parylene HT, one important point is that this fluorinated parylene is very stable under UV wavelength light, compare to classical parylenes (such as Parylene N, C and D) which are very sensible to UV wavelength light. Moreover, Parylene HT , show high reliable dielectric properties in time and at high temperature (85°C) in contact with both the conductive and non conductive fluids. Parylene HT is also a very low polar polymer with a very low water (moisture) absorption (less to about < 0.01%, after 24h in contact with water at 23°C, according to ASTM D570) and is therefore most advantageously used for applications as dielectric layer in contact with water.
Additionally, Parylene HT films have shown high resistance to most chemicals, especially to most non conductive fluids (like chlorinated aromatic alkanes and alkenes or more general halogenated aromatic alkanes that can be used in liquid formulation for electrowetting applications). If need be, the adhesion of Parylene HT on the lower plate, or on the substrate, of the electrowetting device may be controlled by an adhesion promoter between the lower plate (or the substrate) and the Parylene HT layer. The adhesion promoter can be a fluorinated silane or a non fluorinated silane.

The use of Parylene HT allows the formation of a layer having the required dielectric and hydrophobic properties in the same material, for example in a one CVD (chemical vapour deposition) coating step process.
An optical electrowetting device comprising a conductive fluid and a non-conductive fluid, said fluids being non miscible, and an insulating substrate on which both fluids are in contact and form a triple interface, wherein insulating substrate comprises Parylene HT polymer is new and forms another object of the present invention.

In particular, Parylene HT has shown to be a very good solution for low voltage application.
Indeed, in the field of electrowetting devices and especially in the field of optical liquid lens controlled by electrowetting phenomena, one important issue is to obtain a device working at the lowest voltage possible.

The stability of an electrowetting system is dependent upon the choice of liquids, the dielectric material and the operating voltage.Substantial progress is reported herein on use of 300 nm thick poly-tetrafluoro-para-xylylene) (Parylene HT) films for almost 100° of reliable electrowetting modulation at only 15 V. Not only does Parylene HT exhibit improved resistance to dielectric failure as compared to poly(2-chloro-para-xylylene) (Parylene C), but Parylene HT is shown to sustain continuous DC electrowetting to <70° for > 6 hours. Furthermore, Parylene HT has a surface energy such that when electrowetting in an alkane oil ambient, a Young’s angle of about 170° can beachieved without the traditional fluoropolymer top-coat. Also presented is a new and simple model for calculating electric field enhancement when electrowetting in an oil bath. It is shown that Parylene HT is a promising candidate for low-voltage and large-area electrowetting devices such as displays and lab-on-chip

Parylene HT is deposited by vapor-phase-deposition and polymerization of tetrafluoro-p-xylylene. HT films have a dielectric constant of 2.24 at 1 MHz and show less than 2% weight loss in 2 hours at 450°C by isothermal thermal gravimetric analysis. While developing the deposition process of HT films it was found that the film surface morphology showed a dependence on deposition conditions. A systematic study of the surface roughness, refractive index, weight and thickness loss and FTIR of films deposited using different deposition conditions was done to determine the cause of the surface morphology variation




If you don't find what you're looking for, Contact Us. We may have a suitable product that's not listed, or we may be able to develop a material to fit your specific needs. Tel : (02)2217-3442 / Fax : (02)2704-4070