Laser microfabrication in life sciences
Optical lithography is a process of microfabrication to pattern parts of a thin film or the bulk of a substrate. It uses light to transfer a geometric pattern from a photomask to a light-sensitive chemical photoresist on the substrate. During femtosecond laser lithography, the liquid photoresists are converted into solid phase when exposed to femtosecond laser. Creation of the photonic crystals for visible wavelength biosensors and optical-wavelength metamaterials with negative refraction is an example of the applications that require sub 100-nm resolution. The resolution of this level is not achievable with traditional femtosecond laser microfabrication. The objective of the EU-funded FEMTOLITHO (Ultrahigh resolution femtosecond laser lithography for applications in life sciences and display technologies) project was the analysis of different strategies to improve the resolution of femtosecond laser lithography. The main experimental approach to achieve the project objective was to advance two photon polymerisation (2PP) using focused femtosecond laser pulses to form 3D micro and nanostructures in photoresists. This development required automation of experimental variables and motion control. The project group has developed a femtosecond laser system with automated power, polarisation and focus plane control in addition to motion control of the high resolution stages. This enabled better reproducibility and a much higher efficiency in experiments. The 2PP laser system developed by the project group is particularly important as it allows creation of a 3D structure of arbitrary geometry. This enables flexibility in fabrication of novel and complex 3D structures for future application.
Keywords
Laser, microfabrication, lithography, light-sensitive, photoresist, FEMTOLITHO, two photon polymerisation
