From BioInspired Micromachines to Biofueled Autonomous Micropumps – BioPump

The utilisation of catalytic sub-units for the top down realization of nano or micro motors is a very recent field. A few groups have created miniature 'machines' converting stored chemical energy into controlled motion. The one proposed by Mano et al. (partner 2) is very unique. It is the only one operating in physiological conditions which is of great interest for further applications in the field of bioengineering. The basic idea behind this project is that the movement of self propelled micromachines is, in many ways, identical to the reciprocal movement of fluid pumped by non-moving active surfaces. In both cases the movement (the flux of liquid) can be induced by gradients of electric potential, of concentration of solutes, of temperature. This type of phenomenon has been extensively studied in microfluidic channels where liquids are displaced either by external forces (pressure gradients, electric potential gradients) or by integrated pumps. The framework of microfluidics thus seems appropriate for the study of the mechanism of the autonomous biomachines. As up to date there are probably as many proposed mechanisms for these 'micromachines' as micromachines themselves. In this project we will take advantage of microfluidics for a fundamental study of the coupled enzyme system powering the biomachines. We will start by precisely quantifying the fluid velocity field around fixed biomachines (PIV, optical tweezers). Using novel optical imaging techniques, we will map the proton flux associated with the enzymatic reactions which probably induces the motion. We should thus be able to optimize the propulsion efficiency and get a better idea of the mechanism of these self-propelled biomachines. The biomachine synthesis initially proposed by partner 2 relies on numerous parameters: the size and the shape of the machine itself and its environment are not easily controllable. Therefore precise measurements of the relevant observables (velocity, concentrations) are difficult. In order to get new insights into the physics of these self propelled machines and to be able to determine the accurate exponents of the laws governing their movement, we propose to study the fluid movement induced by two electrodes coated with the same enzyme than the ones powering biomachines. By determining the key parameters governing the fluid flow generated by this type of system enclosed in a microfluidic chamber we will therefore try to elucidate the mechanism of enzyme powered self propelled biomachines. Although the present system is millimetric, there is no reason why it could not be applied to micro or even nanoscale pumps and machines. The only requirement is to be able to deposit the enzymes at the desired locations. We will put a lot of efforts to implement enzyme patterning from the millimeter scale to the micron scale, in order to be able to pattern two different types of enzyme on microfabricated electrodes. As we will move towards smaller systems we will have to test and develop new enzyme patterning techniques based on microfabrication methods. A very promising one is the use of UV photo-curable hydrogels. The second objective of this project is to develop autonomous biofueled micropumps. These micropumps will be constituted of an array of interdigitated micron scale electrodes inside a microfluidic channel. These electrodes will be covered with the same both enzymes and polymers used in the biomachines. Following the approach used by partner 1 to develop integrated electrokinetic pumps, we will realize enzyme powered autonomous micropumps, where the pumped fluid (a glucose solution) will be the only source of energy. We propose in the present project a quite complete approach, ranging from very fundamental studies to application oriented experiments in an emerging research area at the interface of many disciplines. The four partners have a long term experience in their field of expertise and are also already used to work on interdisciplinary projects. We therefore expect to obtain quite rapidly significant results that should be able to compete at the highest international level in this hot topic of current research.