PATTERNING OF POLYSTYRENE BY UV-LASER RADIATION FOR THE FABRICATION OF DEVICES FOR PATCH CLAMPING

摘要

Two types of laser patterning are of interest for application in microsystem technology: direct ablation of polymer material for the generation of two or three dimensional shapes such as microfluidic channels, curved shapes or micro-holes and alternatively photo-induced change of chemical or physical properties. An appropriate choice of laser and process parameters enables new approaches for the fabrication of lab-on-chip devices with integrated functionalities. We will present our current research results in laser-assisted ablation and modification of polystyrene (PS) with respect to the fabrication of polymer devices for high throughput planar patch clamping. Patch clamping is a highly sensitive technique used to measure the electrical activity of a cell. It is used in applications which include drug screening where there is demand for high throughput systems (HTS). While there are a few commercially available HTS patch clamping systems on the market using traditional patch clamping materials, there are no systems on the market using novel materials, or for dealing with cell networks - a physiologically important consideration for the developing fields of tissue engineering and understanding cell to cell interactions. This paper presents potential design approaches and processes for producing a polymer based automated patch clamping system. For this purpose laser micro-drilling of PS and subsequent surface functionalization was investigated as function of laser and process parameters. A high power ArF-excimer laser radiation source with pulse length of 20 ns (repetition rate up to 40 Hz) as well as high repetition ArF- and KrF-excimer laser sources with pulse lengths of 4-6 ns (repetition rates up to 500 Hz) were used in order to study the influence of laser pulse length on laser drilling and laser-induced surface modification. Micro-drilling of PS with diameters down to 1.5 μm were demonstrated. Furthermore the localized formation of chemical structures suitable for improved adhesion of single cells and cell networks was achieved on PS surfaces. A photolytic activation of specific areas of the polymer surface and subsequent oxidization in oxygen or ambient air leads to a chemically modified polymer surface bearing carboxylic acid groups well-suited for controlled competitive protein adsorption or protein immobilization. Finally, distinct areas for cell growth and adhesion are obtained. The combination of laser ablation and modification will be discussed for the laser-assisted fabrication of polymer devices for patch clamping.