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Flame-made gas sensor arrays: Membrane-enhanced selectivity for breath analysis

English title Flame-made gas sensor arrays: Membrane-enhanced selectivity for breath analysis
Applicant Pratsinis Sotiris E.
Number 175754
Funding scheme Project funding (Div. I-III)
Research institution Institut für Verfahrenstechnik ETH Zürich
Institution of higher education ETH Zurich - ETHZ
Main discipline Mechanical Engineering
Start/End 01.04.2018 - 31.03.2022
Approved amount 534'004.00
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All Disciplines (4)

Discipline
Mechanical Engineering
Material Sciences
Chemical Engineering
Microelectronics. Optoelectronics

Keywords (10)

Breath Analysis; Fat Burn; Kidney Dysfunction; Lung Cancer; Gas Sensor; Selectivity; Microporous Membrane; Electronic Nose; Chemo-resistive; Flame-spray Pyrolysis

Lay Summary (German)

Lead
Nichtinvasiv, einfach und schnell - dies sind Kerneigenschaften der Atemgasanalyse, einer medizinischen Diagnose- und Überwachungsmethode der nächsten Generation. Dabei wird die Zusammensetzung des Atems analysiert und die Konzentration einzelner Moleküle mit Krankheiten oder Stoffwechselprozesse assoziiert. Chemo-resistive Gassensoren sind durch ihr kompaktes Design, einfache Anwendung und tiefe Herstellungskosten ideal für tragbare Atemmessgeräte. Trotz dieser Vorteile ist deren Erfolg derzeit durch ihre moderate Selektivität, also die Fähigkeit verschiedene Atemmarker voneinander zu unterscheiden, stark eingeschränkt. Dies ist jedoch essentiell für eine zuverlässige Krankheitsdiagnose.
Lay summary

Ziel dieses Projekts ist es die Selektivität von Gassensoren durch die Entwicklung und Anwendung neuer Konzepte massgeblich zu verbessen. Hierfür werden zuvor entwickelte Sensoren zu Arrays (elektronische Nasen) kombiniert um deren Selektivitätseinschränkungen durch intelligente Algorithmen zu überwinden. Sensoren und Arrays werden zudem mit verschiedenen Filtermembranen ergänzt, um deren Selektivität für bestimmte Atemmarker gezielt zu steigern. Die entwickelten Systeme werden miniaturisiert und in tragbare Atemmessgeräte integriert, um sie direkt an Probanden klinisch zu testen. Angestrebte Studien beinhalten die Überwachung der Körperfettverbrennung während Sport und Diät durch einen Atemazetonsensor, sowie die Erkennung von Nierenversagen und Lungenkrebs durch Ammoniak- und Formaldehydsensoren. Diese Systeme sollen kompakt, günstig in der Herstellung und einfach zu handhaben sein, somit ideal für die Verwendung in der breiten Bevölkerung. Dieses Projekt ist Teil von Zurich Exhalomics, einer interdisziplinären Kollaboration zur Förderung der Atemgasanalyse in der Schweiz.

Direct link to Lay Summary Last update: 04.10.2017

Responsible applicant and co-applicants

Employees

Associated projects

Number Title Start Funding scheme
170729 Integrated system for in operando characterization and development of portable breath analyzers 01.12.2016 R'EQUIP
159763 Nanostructured metal-oxide gas sensors for non-invasive disease detection by breath analysis 01.04.2015 Project funding (Div. I-III)
130582 Tailored nano-detectors for early stage diagnosis of ilnesses from the human breath 01.05.2010 Project funding (Div. I-III)

Abstract

Breath analysis is simple-in-use, fast and non-invasive and thus ideal to complement medical diagnostics where conventional methods are too costly and cumbersome to employ. This includes, for instance, the rapid and inexpensive screening of widespread populations for lung cancer or the real-time monitoring of fat burn during exercise. In breath analysis, concentrations of exhaled volatile compounds are measured and linked to certain diseases (e.g. formaldehyde to lung cancer) or metabolic processes (e.g. acetone to fat burn). For hand-held breath analyzers, chemoresistive gas sensors based on semiconducting metal oxides (SMOx) are particularly suitable. They feature a compact design, simple application and low cost in contrast to sophisticated gas chromatography-/mass spectrometry-based techniques. While featuring sufficiently low detection limits, a major limitation, however, remains their lack of selectivity to breath markers. Despite extensive research in the last decades, only few selective chemoresistive sensing materials have been found (e.g. e-WO3 for acetone). What is truly needed are novel strategies that complement chemoresistive sensing.This can be achieved, for example, by integrating sensors with different selectivity into sensor arrays, the so-called electronic noses (E-noses). These are capable to selectively detect and monitor breath markers and their patterns when no selective sensing material exists. This is important for early stage detection of certain diseases such as cancer and to monitor the physiological state of the human body. Also, microporous filter membranes can increase the selectivity of sensors and E-noses by pre-separating gas mixtures. That way, interfering analytes are held back by molecular sieving, adsorption and chemical separation. In the ideal case, only the target breath marker reaches the sensor leading to exceptional selectivity. These concepts are modular, so they can be developed independently and combined to overcome current selectivity limitations of SMOx sensors.The goal of this project is to introduce these concepts for selective breath analyzers in medical applications. It is a follow-up of SNF projects #159763 and #130582 and will build on nanostructured high-performance SMOx sensors developed there (including Si-doped MoO3, Ti-doped ZnO and e-WO3). Such sensors with strong and different selectivity will be combined into novel orthogonal E-noses enabling higher selectivity than state-of-the-art SMOx. Their performance will be validated with a variety of breath markers at high relative humidity matching that of the human breath. Statistical analysis algorithms will be improved and the influence of humidity will be included into a computational model to further improve selectivity. To increase the orthogonality of E-noses even further, new selective sensing materials will be developed and characterized by material and surface analysis. As filters, microporous membranes based on zeolites will be made on porous substrates by hydrothermal synthesis. They will be decoupled from the sensor material to enable separation of breath by adsorption and preferential permeation. Their performance will be evaluated by sensor measurements with simulated breath and linked to membrane structure and chemical properties. This will be done by material and surface characterization techniques as well as adsorption/diffusion measurements. By varying the membrane composition, framework type, inclusion of dopants or chemical surface modifications, membranes will be developed that enable selective detection of breath markers for which no selective sensor exists. For material and surface characterization of sensor materials and membranes, state-of-the-art techniques available at PTL will be employed including BET, XRD, Raman, FTIR, UV/vis as well as additional techniques readily accessible at ETH such as AAS, MAS NMR, TEM and SEM imaging.E-noses and membrane filters will be miniaturized and integrated into portable breath analyzers to test them directly on humans capitalizing on earlier developments at PTL that have been employed in industry now. This will enable the non-invasive detection and monitoring of diseases in real-time. Studies will focus on monitoring of fat burn and the detection of diabetes by exhaled acetone, hemodialysis monitoring by ammonia, and the detection of lung cancer by formaldehyde. Measurements will be performed under real breath conditions und by comparison with blood markers involving a large number of volunteers. Breath and blood marker tests will be done in collaboration with the Department of Pulmonology (Prof. Dr. Malcolm Kohler) at the University Hospital of Zürich where an ethical permission has been granted already by the Kantonale Ethikkommission (KEK-ZH-Nr. 2015-0675). This research will be part of the Hochschulmedizin Zurich flagship project Zurich Exhalomics, an interdisciplinary collaboration of experts from both technical and clinical areas of ETH Zurich, University Hospital Zurich, University of Zurich, University Children’s Hospital Zurich (Kispi) and EMPA. This project will contribute to the education of two PhD students in the development of sensors and membranes and in applying the resulting systems to clinical applications in breath analysis. Participating BSc and MSc students will gain insight into this fascinating engineering field in semester projects and BSc/MSc Theses. The results of this project will be presented at international conferences and published in peer-reviewed journals.
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