We present a simple pneumatic setup for easy and precise control of pairs of inlet flows for lab on a chip applications.

We present a channel geometry that allows for clean switching between different inlets of a microchip without any contamination of the inlets or the downstream flow. We drive this virtual valve with a pneumatic pressure setup that minimizes disturbance of the downstream flow during the switching procedure by simultaneous variation of the pressures applied to the different inlets. We assess the efficiency of the setup by spectroscopic measurement of downstream dye concentrations, and demonstrate its practical utility by sequentially constructing multiple layers of alginate hydrogel. The method is potentially useful for a whole series of further applications, such as changing perfusion liquids for cell culture and cell analysis, metering, chemical-reaction initiation and multi-sample chromatography, to name a few.

Arsenic and other pollutants are often present in trace amounts in drinking water in a number of countries. In aqueous solutions the sensitivity of arsenic-responsive bacterial bioreporters is far better than the performance of chemical field test kits. However, biological detection currently requires extensive handling and expensive fluorescence microscopy. We fabricated and tested microfluidic chips with fluorescent (GFP) E. coli bacteria that respond to arsenic. Measurement results of fluorescence intensity as function of arsenic concentration and exposure time are promising, showing a clear response to concentrations of 50 μg/l of arsenite.

Recently, short animated image sequences have become very popular in social networks. Most animated images are represented in GIF format. In this paper we propose an animated JPEG format, called aJPEG, which allows the standard JPEG format to be extended in a backward compatible way in order to cope with animated images. After presenting the proposed format, we illustrate it using two prototype applications: the first in form of a GIF-to-aJPEG converter on a personal computer and the second in form of an aJPEG viewer on a smart phone. The paper also reports the performance evaluation of aJPEG when compared to GIF. Experimental results show that aJPEG outperforms animated GIF in both file size overhead and image quality.