Martin F. Jensen

Microstructure fabrication with a CO2 laser system: characterization and fabrication of cavities produced by raster scanning of the laser beam

In this paper we describe the use of a CO(2) laser for production of cavities and microstructures in poly(methyl methacrylate) (PMMA) by moving the laser beam over the PMMA surface in a raster pattern. The topography of the cavities thus produced is studied using stylus and optical profilometry and scanning electron microscopy (SEM). The microstructures display artifacts from the laser ablation process and we describe how the laser ablation parameters can be optimized in order to minimize these artifacts. Using this technique it is possible to generate structures with a depth from 50 microm and a minimum width of approximately 200 microm up to depth and widths of several mm, governed by the beam size and the laser settings.

Rapid prototyping of polymer microsystems via excimer laser ablation of polymeric moulds

This study presents a novel method for rapid prototyping of polymer microsystems. The method is based on excimer laser ablation of a thermally and mechanically stable polymer, such as PEEK (poly-ether-ether-ketone). A negative of the desired microsystem is laser machined in PEEK, which can then be used directly for hot embossing or injection moulding of a series of prototypes. This approach is very rapid and considerably cheaper than more traditional approaches to toolmaking, while still performing well in terms of reproduction of tool dimensions. The reduction in time and cost for a master tool using this method opens up new possibilities for testing small series in the R&D phase of a microsystem. Finally, two particular applications of the technique are presented.

Refractive microlenses produced by excimer laser irradiation of poly (methyl methacrylate)

A method has been developed whereby refractive microlenses can be produced in poly (methyl methacrylate) by excimer laser irradiation at λ = 248 nm. The lenses are formed by a combined photochemical and thermal process. The lenses are formed as depressions in the substrate material (negative focal length), which makes replication necessary in order to obtain lenses with a positive focal length. The method allows for considerable flexibility with respect to the pattern of lenses and the properties of the individual lenses. In this investigation it was possible to vary the diameter of the lenses between 30 and 500 µm and the focal lengths between 300 µm and several mm.

Polymer-microstructures - are they applicable as optical components?

We present a new method to manufacture arrays of microlenses with varying diameter and/or varying focal length on the same substrate material. The method combines direct laser machining with a casting method and is based on the exposure of poly-methylmethacrylate (PMMA) to an UV Excimer Laser (248 nm). A following thermal treatment of the PMMA results in spherical caps in the PMMA which subsequently serves as a mould to replicate inverse structures in poly-dimethylsiloxane (PDMS) by casting. Lenses with a focal length of 300 µm to 4,000 µm have been realized in a PDMS replicate from the PMMA, however, this method is not limited to these materials if the soft embossing technology is applied where an elastomer such as PDMS serves as the mould.

Combined laser texturing and molecular vapor deposition for wetting angle control

In this paper we will discuss various aspects of surface engineering. This is a broad term, and we choose to focus on two aspects thereof, namely surface texturing on the micron scale using laser micromachining, and chemical modification of the surface using molecular vapour deposition (MVD). First, we will discuss the basics of laser texturing, followed by a brief review of contact angle theory. We will then demonstrate how to obtain superhydrophobic surfaces on any kind of material using a combined laser and MVD process. Finally, we will present a few recent industrial cases.

Laser micromachining at the Danish Technological Institute

The laser micromachining activities at the DTI have been going on since 2002. Here, we provide a review of the development of our laser laboratory including our recent investment in a femtosecond laser facility. In-depth information about the capabilities of this facility compared to the other lasers will be given. Finally, several industrially relevant case stories will be presented.