Time and place
Thursday, 24 April, at 13:00, Bldg. 421, Aud. 074
Principal supervisor
Professor Rafael Taboryski, DTU
Examiners
Professor Stephan Sylvest Keller, DTU
Professor Han Gardeniers, University of Twente
Manager Mikkel Fougt Hansen, KLA
Chairperson at defence
Associate professor Ada-Ioana Bunea, DTU
Abstract
Achieving carbon neutrality requires precise monitoring and optimization of technologies across various domains, including tracking greenhouse gas emissions, advancing renewable energy, improving carbon capture and storage (CCS), and supporting a circular carbon economy. Mass spectrometry (MS) plays a crucial role in this effort, offering unparalleled analytical capabilities for gas-phase monitoring. It provides the scientific foundation necessary to ensure efficient, sustainable processes critical to mitigating climate change. However, Many carbon-neutral technologies require gas analysis in liquid phases, posing a significant challenge for traditional MS techniques, which rely on separate sampling systems for each phase. This complexity necessitates specialized interfaces that enable direct gas analysis within liquids, a crucial step for real-time optimization of carbon-neutral processes. However, existing solutions often suffer from one or more limitations, such as low sensitivity, slow response times, or interference from high solvent evaporation, making them less effective for direct liquid analysis.
To address these challenges, the nano-perforated membrane chip (NPMC) has been developed as an improved iteration of existing designs. Leveraging advancements in microfabrication, NPMC seamlessly integrates with electrochemical mass spectrometry (EC-MS), enhancing its capability for real-time gas analysis in liquid environments. Leveraging advances in microfabrication, the nano-perforated membrane chip (NPMC) has been developed, to integrate seamlessly within electrochemical mass spectrometry (EC-MS). This breakthrough addresses the current limitations of membrane chip technology, enabling direct, real-time analysis of dissolved volatiles without the need for cumbersome sampling procedures. The NPMC functions by transferring dissolved volatiles from the liquid phase to the vapor phase through evaporation, using an inert carrier gas to transport analytes through a pressure-matching microcapillary into the mass spectrometer.
The thesis introduces the fabrication process of NPMC, its integration with EC-MS, and how its capabilities have facilitated the transition to in-line mass spectrometry (IMS) for real-time gas analysis. NPMC is fabricated at wafer scale using advanced microfabrication techniques on monocrystalline silicon wafers. Its design incorporates a suspended nano-perforated membrane (NPM) on one side and a gas channel system on the other. Two robust and reproducible fabrication strategies for NPM formation were developed and demonstrated, addressing key challenges in its production. These strategies involved nanopore etching through either the DREM (Deposit, Remove, Etch Many times) or ORE (Oxidize, Remove, Etch) processes. The fabrication process integrated sidewall protection techniques, thermal oxidation, and PECVD oxide deposition, followed by rapid thermal oxidation and isotropic silicon etching to achieve the desired nanopore structure.
By enhancing the NPMC’s ability to operate at pressures exceeding atmospheric levels, several bulky components of EC-MS were eliminated, paving the way for in-line mass spectrometry (IMS). This advancement enabled direct real-time monitoring of dissolved volatiles in liquid-phase environments without painstaking error-prone gas sampling and treatment processes!
To assess the capabilities of IMS-NPMC using water vapour as the carrier gas, its performance was benchmarked against conventional instruments used for measuring dissolved volatiles in bulk liquid, as well as off-gas analysis systems, assessing its ability to capture all analyte variations observed by traditional methods while identifying previously undetected changes. The results established IMS-NPMC as a transformative technology for in-line process monitoring, particularly in bioreactors and industrial applications requiring continuous real-time gas analysis.
These advancements, explored as part of a Ph.D. thesis, set the foundation for future innovations in real-time gas analysis. The work demonstrates how in-line MS, powered by NPMC technology, offers cleaner, more efficient, and scalable solutions for a sustainable future. As industries strive for net-zero emissions, in-line mass spectrometry will remain at the forefront of innovation, turning carbon neutrality from an ambitious goal into a tangible reality.
