What are they?

Flexible whole cell biosensor is an appealing field. Whole-cells are a natural factory of biocatalysts. Usually, the method for acquiring isolated biocatalysts, like the enzymes, requires a process of separation and purification from the raw whole-cell strain or tissue, which is tedious, time and resource consuming. Furthermore, added advantage of whole cell biosensor over enzyme biosensor are that the enzyme sometimes requires cofactors and coenzymes, to carry out a complete reaction or to recognize a substrate, which implies a recycling process to attain the required cofactor, then the need for further separation and purification steps. Whole-cells contain a complete metabolic aggregate of enzymes, cofactors and coenzymes. Analog processes can be found in tissues. The requirements related to maintenance and cost for culturing microorganisms are below from those of tissue cultures.

...continue reading "Electrochemical Sensing With Cells: Whole Cell Electrochemical Biosensors"

We all have them in our phones: MEMS (Micro Electric Mechanical Systems). Inertial MEMS, for instance, are the tiny accelerometers and gyroscopes in our smart phones. They make playing games on the phone more fun and help us finding the next pizza restaurant. To do that, they measure our movements by recognizing rotation and acceleration. MEMS are really tiny, i.e. in the micro-meter (µm) size regime. You need special microscopes to see their set up in detail, e.g. a scanning electron microscope. However, people are trying to make them even smaller. Why? Well, there are many reasons and of course one of them is the cost. If the devices were smaller, the production cost would also decrease.

The MEMS accelerator and the gyroscope are two of the most important examples of the growing zoo of MEMS. Therefore, we will take them as examples in our discussion on what limits the shrinkage of MEMS? To give an overview, we will first consider some general aspects of dimension scaling. Then we will proceed to more specific aspects which limit the area shrinkage of an inertial MEMS.

...continue reading "What Limits the Shrinkage of Inertial MEMS?"

To compare and predict the performance of heterogeneous catalysts, it is important to have a standard way to describe the catalytic activity. The  catalytic activity describes how good a catalyst is working for a given reaction. When we have a normalized measure for the catalytic activity, we can compare different catalysts and find out which is the best one. But this means, that we have to do a lot of experiments and try and fail until we found a good catalyst. It would be better, if we could predict whether a material will be a good catalysts for a given reaction or not.

The catalytic activity is dependent on the physical and chemical properties of the catalyst material, and of course the reaction conditions, i.e. temperature, pressure and the reactant concentrations. So, if we want to predict the catalytic activity of a material, we have to have information about the material's properties. As we will see in the following, a few parameters can be sufficient to get an idea on the performance of a material as a catalyst for a given reaction. To predict the catalyst quality we can use the Sabatier principle.

...continue reading "Principles for the Design of New Heterogeneous Catalysts"

CO2 is a greenhouse gas and to reduce its concentration in the atmosphere, there are three possibilities: We can minimize its production, we can store it and we can use it to make other chemical compounds. Scientists are trying realize all three possibilities to reduce the CO2 concentration in the air. There are several challenges to face, such as to make the 400ppm CO2 content of the atmosphere into usable quantities of CO2 in proper density.

Of course, it would be nice to transform CO2 into "value-added" chemicals, which are for instance methanol, fuels or methane. There are several catalysts that can transform CO2 into these chemicals and research is done to optimize these catalysts for an efficient industrial use.

...continue reading "Transforming Carbon Dioxide into Methane!"