Micro-lens array manufacturing by using an inkjet printing technology allows for the manufacturing of large area arrays on lithographically structured substrates that contain oleophobic and oleophilic surface patterns. An inkjet printing process deposits the high performance, hybrid polymer ORMOCER on the oleophilic pattern. The material forms by means of surface tension and wetting boundaries a lens shape, while the inkjet printing process itself enables for a highly parallel manufacturing of many lenses at the same time. A typical geometrical deviation <2% of the radius of curvature for lenses with diameters of <1 mm, ROC’s of ca. <2 mm and sag heights of <100 microns was achieved. Also a specific lithography processing regime was derived that combines wetting patterns with optical apertures to enable advanced illumination setups like multi-aperture projection.
While lab-on-a-chip systems have become more and more widely used in many fields in diagnostics, analytical and life sciences, most of the systems still have to be considered as stationary, typically desktop-sized instruments. While the actual microfluidic cartridge often is comparatively compact, the associated instrument to operate this cartridge remains large, limiting the use of such systems in applications outside of a laboratory environment. Two main aspects contribute to this situation: Detection systems, especially sensitive optical (e.g. fluorescence) detection systems remain relatively large. The fluidic control elements, especially when reagents have to be delivered from a reservoir in the instrument to the cartridge, also contribute to the system size and weight. We have tried to circumvent these problems by integrating both the detection system as well as all required liquid reagents into the disposable microfluidic cartridge. The technology used for the realization of the detection system is the multilayer inkjet-printing of organic semiconductor materials (PEDOT:PSS) in order to create light sources and photodetector elements directly on the cartridge. This printing technology can be seamlessly integrated into the manufacturing workflow of the cartridge fabrication. All liquid reagents (currently 6) for an exemplary immunoassay on this platform are integrated using blisters which can be easily actuated either manually or by a simple linear actuator. Data readout as well as system control are planned to be executed using a smartphone, thereby further reducing the complexity and size of the instrument.
Inkjet printing is a digital printing technique that is capable of depositing not only inks, but functional materials onto different substrates in an additive way. In this paper, applications of inkjet printed structures for microfluidic lab-on-chip systems are discussed. Such systems are promising for different chemical or biochemical analysis tasks carried out at the Point-of-Care level and therefore due to cost reasons are often fabricated from polymers. The paper discusses inkjetprinted wiring structures and electroactive polymer (EAP) actuators for use in microfluidic lab-on-chip systems. Silver and gold wirings are shown that are fabricated by printing metal nanoparticle inks onto polymer substrates. After printing the structures are sintered using argon plasma sintering, a low-temperature sintering process that is compatible with polymer substrates. The wirings consist of several electrode like structures and contact pads and feature minimum structure sizes of approximately 70 μm. They can be used for electrodes, fluid presence detectors and localized ohmic heaters in lab-on-chip systems. Based on that an all inkjet-printed EAP actuator then is discussed. Membrane-type bending actuators generate deflections of approximately 5 μm when being driven at a resonance frequency of 1.8 kHz with 110 V. Derived from that and assuming passive valves on-chip pumping rates in the range of 0.5 ml/min can be estimated.