Juan Li1, Douglas Mair2, Harish Padmanabhan1, Nick R.Glass1, and Justin J. Cooper-White*1,3,4,5


1Australian Institute for Bioengineering and Nanotechnology, the University of Queensland, Brisbane, Australia.
2Australian National Fabrication Facility (QLD Node), Brisbane, Australia
3School of Chemical Engineering, the University of Queensland, Brisbane, Australia.
4 Manufacturing Flagship, CSIRO, Clayton, Victoria, Australia
5UQ Centre for Stem Cell Ageing and Regenerative Engineering (UQ-StemCARE), the University of Queensland, Brisbane, Australia
Building 75,Cnr College Rd & Cooper Rd, AIBN, Brisbane City QLD, Australia


Soft lithography, especially the micro-molding technique, has been used extensively to fabricate microfluidic devices(Xia and Whitesides 1998). Among mold fabrication techniques, photolithography plays a pivotal role due to its high throughput and simple execution. Standard multi-layered photolithography can only produce 3D-like structures in subsequent layers, which constrains device designs and therefore limits potential applications of microfluidic devices. To overcome this, various methods have been applied. One common approach is to reflow positive resist to form curved structures to achieve a valve function (Unger, Chou et al. 2000). This significantly extends the capability of microfluidic devices, although the integration of positive resist and negative resist (most commonly, SU8) is difficult to control and leads to the requirement of advanced fabrication skill and often leads to low yield of mold production(Fordyce, Diaz-Botia et al. 2012). In this work, we have developed and optimized a method by which we can fabricate arbitrarily shaped structures together with conventional features in a concise, explicit and high throughput manner. This is accomplished by combining Nanoscribe with standard photolithography technology. Nanoscribe is a relatively new 3D nano-printing technology (NanoscribeTM) that can achieve nanoscale features with high reproducibility. Initially, the optimal fabrication conditions of Nanoscribe adapted to SU8 were studied as seen in Figure 1. We then applied this technique to fabricate complex features and subsequently align these with a photomask to achieve a mold with various shapes and scales of features efficiently and accurately out of a single photo resist layer. The combination of these two techniques avoids the time consuming and low yield multi-layered and/or multi-resists photolithography and reduces the technical requirement of operators. Above all, it significantly extends the potential structural diversity and fabrication accuracy of microfluidic devices. Ultimately, this approach can facilitate the development of next generation microfluidic devices for chemical, biological, optical, and electronics applications.