Integrated photonic lab-on-chip systems for biomedical applications

Abstract

Currently, one may find a wide variety of approaches for integrated lab-on-chip systems developed for applications in the biomedical field. Our contributions within the area of polymer based photonic systems are presented here. We are utilizing mass production techniques and head for lab-on-a-chip systems with solely optical and fluidic interfaces, avoiding electrical interconnects. Fluidic structures are implemented in the chips mainly by using the same technologies, which are chosen to create the optical elements. While photonic structures may require dimensions in the sub-100 nm range, microfluidic channels are more than one order of magnitude above this regime. Nevertheless, our approach allows for a limited number of process steps by simultaneous multiscale fabrication. Organic semiconductor lasers are generated by evaporating a thin film of photoactive material on top of a distributed feedback (DFB) grating. Gratings are replicated by hot embossing into poly(methyl methacrylate) (PMMA) bulk material. The lasing wavelength in the visible light regime of the on-chip lasers is selected by altering the thickness of the vacuum deposited organic semiconductor active material or the DFB grating period. Waveguides are monolithically integrated in PMMA via photodegradation through deep ultraviolet irradiation. The coupling of laser light into these waveguides is optimized. Hence, laser light is guided to an interaction zone with a biological sample in the microfluidic channel on chip. Micro-optical cavities are designed and processed to be functionalized for detecting biological binding events in the channel. Surface functionalization, e.g. by Dip-Pen Nanolithography, is carried out for integrated label-free detection as well as for fluorescence excitation.