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PhD Defence Divya Balakrishnan

acidity control in miniaturized volumes: engineered microreactors for high throughput chemical reactions

Divya Balakrishnan is a PhD student in the research group Biomedical and Environmental Sensorsystems (Bios). Her supervisors are W. Olthuis and A. van den Berg from the Faculty of Electrical Engineering, Mathematics & Computer Science.

The miniaturised regulation of acidity has the potential to increase the speed of the chemical reactions that are used on the synthesis of different polymers including the DNA and the proteins, through the control of their structure and introducing a multiplexed manipulation in several addressable regions can increase the throughput for combinatorial chemistry. The electrochemical means to control the acidity would offer a compact, low cost technology, with the integration of microfluidics and electronics that could function as a micro-total-analysis system for on-demand assembly or manipulation of biopolymers. Here the challenge lies on the miniaturised production and the confinement of the protons with a design that allows multiplexed processes. In this thesis, we present our research advances towards this end. First we study the molecule 4 Aminothiolphenol (4ATP) that when polymerised can reversibly generate the protons through electrochemical redox reactions. The different methods to polymerise 4ATP are investigated. The electrochemical behaviour of the different methods with respect to their charge transfer capacitance and reversibility of the redox reactions are measured and compared.  Then we show the design of the microfluidic platform that integrates microfluidic and electrical connections. The platform can hold an exchangeable chip that contains the electrochemical reactor. The working model and the demonstration of miniaturised acidity control in one microreactor chip (~100 nL volume) mounted on the platform is shown where the acid is generated reversibly through the generation of protons from the polymerised 4ATP molecules.  The stability of the generated acid to confine the protons in the cell is also investigated.  The multiplexed control of acidity is studied by the second design that contains further miniaturised four electrochemical reactors on a chip with each cell holding a volume of ~3 nL. The demonstration of multiplexed control is shown on the platform with two of the electrochemical reactors that could be driven to maintain contrast acidity conditions.