Design of a valveless organ-on-chip micropump

Abstract

In the last few years organ-on-chip (OoC) has been emerging as a new method for more reliable research to screen the effects of new drugs on the body. This is a novel technology mimicking the in vivo environment of tissue cells, making it a more suitable candidate for experimentation than traditional 2D cell cultures. However, in order to ensure smooth and swift implementation of this technique, some issues must be addressed first. One of these issues concerns perfusion: most OoC devices require external equipment to provide the necessary dynamic flow that makes the OoC unique, so that cells experience continuous fluid shear and are perfused sufficiently. In this thesis a model of an on-chip electro-polymeric pump is designed for application on an OoC. From a background study the design aims are defined: a membrane actuated pump with a nozzle-diffuser channel providing pump action. The membrane is made from ionic polymer-metal composite (IPMC), a material that deforms under electric current which is produced at TU Delft with the intention to use it in OoC applications. Its low voltage operating range and its biocompatibility make it an excellent candidate for this. Furthermore, the nozzle-diffuser elements avoid the need for moving elements inside the channel, instead providing pump action based on a pressure gradient over the nozzle elements. Finally, three design aims are defined, being: high flowrate, high flow pulse and low flow rate and pulse applications, corresponding to various needs in the OoC field. A base model is designed using COMSOL Multiphysics software, using similar devices described in literature. The model consists of a combination of solid mechanics (for membrane movement), fluid mechanics (for flow movement) and a fluid-structure interaction module to combine the two. This model is then tested for a range of parameters, first independently and later in pairs. General conclusions drawn from these simulations include: - Between the membrane displacement and -frequency (which can both be varied after fabrication), the membrane displacement magnitude affects the output more significantly than actuation frequency - The membrane width is positively correlated with flow rate output and pulse amplitude - The channel depth is positively correlated with flow rate output, but only if the membrane displacement scales along with it - A long slender nozzle yields lower flow output than a short, squat nozzle - The results from this model are consistent with nozzle-diffuser theory, stating that nozzle resistance and membrane movement affect the flow most significantly. This leads to three designs according to the three application wishes expressed earlier. The pump is designed such that it can be manufactured on a silicon wafer using electronics cleanroom equipment. The combination with the process developed for IPMC provides a novel pumping mechanism that has the potential to fully integrate an important aspect of an OoC on-chip, greatly increasing user friendliness and allowing for wider implementation of this technology.