Abstract: The present invention relates to an apparatus for producing electrospun polymer fibres with a modified surface, processes for producing a polymer fibre with a modified surface, non-woven polymer fibre mats or meshes comprising an electrospun polymer fibre, including multi-layered electrospun polymer fibre meshes, and a kit including a directional plasma device.

Abstract: A gas laser 10 has a gas-field enclosure 12 in which electrodes 14, 16 are operable to excite the gas within the enclosure to emit laser radiation. The region 20 between the electrodes 14, 16 contains a plasma which emits the laser radiation. At one end of the enclosure 12, there is a plasma-free region 22 undivided from the region 20. A microphone 24 is located in the plasma-free region 22. This detects pressure waves occurring in the plasma-free region when laser radiation is absorbed. The signal from the microphone is used to control a feedback circuit 26 to stabilize the frequency of the emitted laser radiation.