Time and place
18 June 2024, 13:00, bldg. 341, aud. 23, DTU Lyngby Campus
Principal supervisor
Professor Stephan Sylvest Keller
Co-supervisors
Professor Jenny Emnéus
Senior Researcher Arto Heiskanen
Examiners
Associate Professor Maria Dimaki, DTU Bioengineering
Professor Bernhard Wolfrum, TUM
Professor Heungjoo Shin, UNIST
Chairperson at defence
Professor Henri Jansen
Abstract
Our society is on a broad scale moving towards increased use of wearables, implants, point-of-care, internet-of-things, and lab-on-a-chip systems. All of which require device miniaturization. Electrochemical sensing integrated within these systems offer huge benefits. The most well-known examples of electrochemical (bio)sensing are probably the glucose monitor and gas monitoring of toxic gases. However, the complex samples from both the human body and the environment require development of the sensing platforms to further enhance signals. Meanwhile, for miniaturization of devices, it is important to improve or maintain performance as the size is reduced.
One way to enhance the electrical signals generated in electrochemical sensing is by decreasing the gap between two electrically separate electrodes to the micro- and nanometer scale. This enables electrochemical redox cycling. It is a phenomenon in which the current generation from a single molecule can be tremendously amplified. The signal enhancement arises as the molecule is repeatedly transferring electrons at two electrically separate electrodes as it cycles back and forth. This is opposed to normal electrochemical sensors in which only a single electron is transferred per
molecule. One can think of it as a way of recycling the signal from a single molecule.
This thesis explores the fabrication of different pyrolytic carbon micro- and nanogap electrode platforms and approaches that can facilitate miniaturization to improve electrochemical sensing performance. The main pyrolytic carbon electrode systems developed were interdigitated microelectrodes with micro gaps and stacked layer electrodes with nanogaps (SLNE). This is the first time SLNE has been demonstrated with pyrolytic carbon. SLNE had gaps of 89 nm and were achieved in large arrays,
combining the pyrolytic carbon fabrication technology with atomic layer deposition.
SLNE demonstrated an electrochemical signal amplification upwards of 38 and detection of 25 nM dopamine. Other methods of fabrication for micro- and nanogap electrode were developed such as reactive ion etching of pyrolytic carbon. The pyrolytic carbon micro- and nanogap platforms developed here offer extensive opportunities within electrochemical sensing due to their potential of integrating precise and controlled nano- to macroscale fabrication.
