M.H. Goedbloed

Adhesion and patterning of cortical neurons on polyethylenimine- and fluorocarbon-coated surfaces

Adhesion and patterning of cortical neurons was investigated on isolated islands of neuron-adhesive polyethylenimine (PEI) surrounded by a neuron-repellent fluorocarbon (FC) layer. In addition, the development of fasciculated neurites between the PEI-coated areas was studied over a time period of 15 days. The patterns consisted of PEI-coated wells (diameter 150 /spl mu/m, depth 0.5 /spl mu/m) which were etched in a coating of fluorocarbon (FC) on top of polyimide (PI) coated glass. The separation distance between the PEI-coated wells were varied between 10 and 90 /spl mu/m. This paper shows that chemical patterns of PEI and FC result in highly compliant patterns of adhering cortical neurons after 1 day in vitro. Interconnecting neurite fascicles between PEI-coated wells were especially present on patterns with a separation distance of 10 /spl mu/m after 8 days in vitro. A significant lower number of interconnecting neurite fascicles was observed on 20 /spl mu/m separated patterns. Effective isolation of neurons into PEI-coated wells was achieved on patterns with a separation distance of 80 /spl mu/m as no interconnecting neurite fascicles were observed.

Fine tuning the roughness of powder blasted surfaces

Powder blasting (abrasive jet machining) has recently been introduced as a bulk-micromachining technique for brittle materials. The surface roughness that is created with this technique is much higher (with a value of Ra between 1?2.5 ?m) compared to general micromachining techniques. In this paper we study the roughness of powder blasted glass surfaces, and show how it depends on the process parameters. The roughness can also be changed after blasting by HF etching or by using a high-temperature anneal step. Roughness measurements and scanning electron microscopy images show the quantitative and qualitative changes in roughness. These post-processes will allow us to investigate the influence of surface roughness on the microsystem performance in future research.

Fine tuning the surface roughness of powder blasting glass surfaces

Powder blasting is a fast and inexpensive directional etch technique for brittle materials like glass, silicon and ceramics. This new micromachining technique is currently extensively used for μ-fluidic devices [1][2]. However, unfamiliarity with this technique sometimes causes a hesitation to use it, especially due to the uncertainty about the effect of the rough surface on the device performance [3]. It is e.g. supposed that the roughness increases the electro-osmotic flow, fluidic mixing and hence the dispersion, although it has not been shown yet. Therefore it is important to be able to manipulate the roughness and study its effect on device performance. This paper shows how the roughness of a powder blasted surface can be controlled by process parameters, or changed with post treatments, both quantitatively and qualitatively.

Optimization and realization of electro-osmotically driven microsynthesis systems

The fabrication, optimization and testing of an electro-osmotically driven microsynthesis system for Wittig reactions are described. For this purpose numerical models have been developed for injection / mixing and system design and optimization.

Electro-osmotic flow control in microfluidics systems

Downscaling of micro chemical systems, often referred to as “Labs-on-a-ehip”, has gained enormous interest during the last five years. The reason is the exploding research and commercial activities in DNA analysis. Chip-sized systems have proven to have many advantages over their “macro” counterparts: due to downsizing analysis often can be done at higher speed with less sample use. Besides, special chemistry can be performed which is not always possible in macro reactors due to explosion risks or toxicity for instance. Microchemistry chips have also proven to be convenient to use as shown by the Caliper chips used by Agilent [1]. We believe there is even a bigger market for synthesis chips since the advantages of analysis on micro scale also count for synthesis systems and secondly often a few synthesis steps are involved in analysis. An interesting field is chemical process development in which chemical processes need to be optimized by performing many time-consuming experiments with different concentrations. This stage largely defines the time-to-market period and the production price of medicines.