Abstract

The idea to shrink a laboratory down to chip size, or at least to integrate some critical lab tasks onto micro devices has been around since over 20 years now. Some of my best years in „lab on a chip“ research have been 1988-95 in Basel, at Ciba-Geigy in Michael Widmer’s research lab. In the meantime, the field has grown significantly, many of my students are now professors in this field, the early patents are all expired, small companies use microfluidics for their products, and the main application focus has shifted from analytical chemistry to cell biology and tissue engineering [1].

Microfluidic chips are usually defined by photolithography masks which are generated from straight lines and CAD programs. The manufacturing process usually gets more complex if multiple depths, i.e. multiple masks have to be used, and variations in depth profile are difficult to achieve. I will present a simple way of obtaining channel structures which feature gradually increasing or decreasing channel depths, and which also can feature irregularities in its surface. At first sight, this may seem inappropriate, may look “ugly” and not engineering-like. However, in biological surroundings, we can see such structures, and they are fully functional.

Plant leaves are used as templates for channel patterns, including its fine structure and including its macroscopic network pattern. Structures are formed in PDMS and covered by glass slides for microscopic observation [2]. Structures are used for investigating cell behaviour.

[1] P Neužil, S Giselbrecht, K L änge, TJ Huang, A Manz, “Revisiting lab-on-a-chip technology for drug discovery”, Nature Reviews Drug Discovery 11 (8), 620-632 (2012). [2] W.Wu, R.M.Guijt, Y.E.Silina, M.Koch, A.Manz, “Plant leaves as templates for soft lithography”, RSC Advances 6, 22469-22475 (2016)