4M Knowledge base - papers

A. Schneider (a), L. Frasson (b), T. Parittotokkaporn (c), F. M. Rodriguez Y Baena (b), B. L. Davies (b),
and S. E. Huq (a)

(a) Science and Technology Facilities Council, Rutherford Appleton Laboratory, Technology – Central Microstructure Facility, Harwell Science and Innovation Campus, Didcot, OX11 0QX, UK
(b) Mechatronics in Medicine Lab., Depart. of Mechanical Engineering., Imperial College, London, SW7 2AZ, UK
(c) Institute of Biomedical Engineering, B 422 Bessemer Building, Imperial College, London SW7 2AZ, UK

Abstract

The development of a novel biomimetic neurosurgical probe is inspired by nature. Some insects have spines with a unique surface texture which enables them to penetrate tissue more easily. This surface texture consists of cutting teeth and fin-like pockets on the spine. Instead of drilling, the insect slides its spine into the fibre through the reciprocating motion of independent segments. Applying the same or similar microtexture to a miniaturized neurosurgical endoscope could improve existing tools for brain surgery and brain biopsy. The development of such endoscope could minimize the damage caused by inserting the probe whilst avoiding the risk of buckling, which is a common occurrence when thin flexible probes are axially loaded.
To replicate the surface microtexture, teeth and fin-like high-aspect-ratio microstructures were fabricated. Different geometries of these fins and teeth were studied for insertion into tissue so that the texture could be characterized for friction and tribological interaction with tissue. For these tests, free-standing long and narrow strips with microstructures in up to 525 μm thick SU-8 were designed, fabricated, and mounted onto prototypes made by
stereolithography. This paper focuses on the fabrication of the microtextured strips. The required geometry of these
strips can cause considerable bending. The structures were investigated regarding fabrication and stress conditions.

R. Jurischka (a), Ch. Blattert (a), I. Tahhan (a), A. Schoth (a), H. Reinecke (a),
a Laboratory for Process Technology, Institute of Microsystem Technology, University of Freiburg, 79110 Freiburg, Germany

Abstract

Present main applications of microfluidic devices are within the life sciences or chemical analysis. Polymers are ideally suited for these applications due to their material properties and their applicability for high volume production. In this study, we developed a rapid manufacturing technology for disposable microfluidic devices using UV-LIGA and injection molding. Exchangeable inserts for the molding tool were fabricated by a modified UV-LIGA technology. The UV-LIGA process is based on a SU-8 lithography with a metal substrate, which allows for a reduction of the nickel electroplating time. These inserts enable a cost effective structuring of polymers. Different prototypes of chips for microfluidic applications with channel dimensions down to 10 μm and aspect ratios of 8 have been fabricated. The electroplated nickel structure has a hardness of 800 Vickers and an excellent top surface roughness of Ra < 20 nm. Taper angles of 3-8 degrees result in low demolding forces. The main advantage of our rapid processing technology is the availability of the geometry, the specific target material and manufacturing technology right from the start of the development to a cost effective high volume production of microfluidic devices.