Direct Laser Interference Patterning

Modification of polymer surfaces is used to improve biocompatibility or to provide medico-functionality of blood- and tissue-contacting medical devices. Yu et used Direct Laser Interference Patterning (DLIP) to prepare periodic micropatterns in polymers for study of contact guidance of mammalian cells. 

Lasagni A, Acevedo D, Barbero C, Mticklich F. (2006) One-step production of oiganized surface architectures on polymeric materials by direct laser interference patterning. Ado Eng Mater 99-103. 

Acevedo DF, Lasagni A, Barbero CA, Miicklich F. (2008) Micro/nano fabrication of surface architectures on polymers and copolymers using direct laser interference patterning. Proc Mat Res Soc Symp 1054 FF01-FF07. 

Commercial polymer films can be easily microstructured using Laser Interference Patterning. In that way, the scope of the technique is increased since materials having well-known bulk and surface properties can be microstructured, allowing direct application, for example, in biomedical devices poly(etheretherketone) resists sterilization by radiation or heat treatment and it has been used to produce kidney dialysis machine components poly(etherimide) is used in harmonic scalpels polycarbonate (PC) is used in electrophysiology cathethers and poly(imide) (PI) is used in off pump coronary artery bypass devices.Moreover, the surface of already fabricated systems could be modified using this technique since it can be applied in air without altering the shape of the samples. 

Interference lithography makes use of the interference pattern which is formed when two or more coherent light waves are superposed. In a t3q>ical optical set-up, a laser is used as a source for UV radiation. The laser beam is spht into two beams. Each of the beams is directed by mirrors towards a substrate coated with photoresist where the beams are superposed after being expanded. Two interfering beams produce a ID grating with a sinusoidal intensity distribution. To this intensity pattern the UV-sensitive photoresist is exposed. After exposure the photoresist plate is developed where exposed or unexposed. Photoresist is removed depending on the type of photoresist. As the intensity profile is sinusoidal continuous microstructure profiles will result in general. 

Two-wave laser interference (Fig. 20(a)) may be used to record periodic elements with subwavelength features (A 100 nm). The UV laser (for example helium cadmium, argon-ion, or excimer laser) beam is focused down with an objective lens and passed through a matching pinhole to spatially filter the beam. The central part of the emerging spherical wave, which has nearly planar phase fronts, illuminates the sample directly. A part of the wave is reflected towards the sample as shown. These two waves interfere to produce a standing, periodic intensity pattern with period... 

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