Browsing by Author "Laurila, Tomi, Prof., Aalto University, Finland"

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    Multilayer carbon hybrid based electrodes for direct electrochemical detection of analgesics and biomolecules - Development of an electrochemical sensor for determination of analgesics in blood samples
    (Aalto University, 2021) Wester, Niklas; Laurila, Tomi, Prof., Aalto University, Finland; ; Kemian ja materiaalitieteen laitos; Department of Chemistry and Materials Science; Physical Characteristics of Surfaces and Interfaces; Kemian tekniikan korkeakoulu; School of Chemical Technology; Koskinen, Jari, Prof., Aalto University, Department of Chemistry and Materials Science, Finland
    There is increasing interest in point-of-care (POC) determination of drugs and biomolecules, as well as real-time monitoring of these analytes, with wearable and in vivo sensors. Rapid response POC tests can improve patient safety in situations like poisoning and enable personalized treatments whereas real time detection of physiological processes such as neurotransmission events can improve our understanding of neurophysiology and enable novel treatments for neurological disorders. Electrochemical detection is an attractive technology for both POC in vitro diagnostics and wearable sensors alike, due to its low price, simple instrumentation and small required sample volume. Many analgesic drugs show highly individual dose response and thus a dose that causes dangerous side effects in one patient may lack analgesic effect in another. Analgesics are also some of the most abused prescription drugs. Opioid overdoses kill tens of thousands of people annually in the United states alone. Both intentional and unintentional poisoning of over-the-counter analgesics, such as paracetamol, also regularly occur. Therefore, a quantitative POC test for determination of analgesics in capillary blood samples, could be a powerful diagnostic tool for poisoning. However, the POC determination of small drug and biomolecules in unprocessed blood samples has proven to be difficult. In this thesis, we have investigated the use of tetrahedral amorphous carbon (ta-C) and single-walled carbon nanotube (SWCNT) thin films in electrochemical sensing. We have carried out extensive physicochemical characterization of these electrode materials. We combine synchrotron based x-ray spectroscopy with electron microscopy, diffraction and conventional spectroscopic techniques. Both the studied materials were found to support facile electron transfer and show low background currents enabling highly sensitive detection of dopamine and morphine. They, however, lack the fouling resistance and selectivity required for detection of dopamine and analgesics in complex biological samples. Modification with carbon nanomaterials or polymer membranes significantly improved the selectivity as well as reduced the electrode fouling, allowing for detection of dopamine and analgesics in blood samples without precipitation of proteins. We show that such multilayer electrodes can be tailored for the requirements of detection of neurotransmitters and analgesic drugs. Finally, we demonstrate a process for mass production of electrochemical test strips. These sensor strips were shown to be capable of detecting clinically meaningful concentrations of paracetamol from a 20 µL blood sample in less than 5 min. Based on these results we propose an electrochemical assay for quantitative detection of paracetamol.
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    Nanocellulose / Nanocarbon Composites for Direct Electrochemical Detection of Small Molecules
    (Aalto University, 2022) Durairaj, Vasuki; Laurila, Tomi, Prof., Aalto University, Finland; Kemian ja materiaalitieteen laitos; Department of Chemistry and Materials Science; Physical Characteristics of Surfaces and Interfaces; Kemian tekniikan korkeakoulu; School of Chemical Technology; Koskinen, Jari, Prof., Aalto University, Department of Chemistry and Materials Science, Finland
    Nanocellulosic materials are rapidly developing into highly versatile and sustainable alternatives for synthetic polymers in several high value applications. They are of particular interest in various sensor architectures due to their unique properties such as high strength, large surface area with potential for functionalization, hygroscopicity and film forming tendency. Further, their ability to disperse carbon nanomaterials in stable aqueous suspensions has resulted in an increased interest towards the development of nanocellulose / nanocarbon electrochemical platforms for detection of various drugs and biomolecules in the recent years. However, this field is still in its infancy, and there is an evident need to understand the role of different nanocellulosic materials in tailoring the electroanalytical performance of the resultant nanocellulose / nanocarbon composites. In this thesis, we have used nanocellulosic materials with different geometries and functionalizations, to develop composite electrode architectures with commercial multiwalled carbon nanotubes (MWCNT). The physical and chemical nature of the nanocellulosic materials, MWCNT, and their composites, are studied using several surface and bulk characterization methods and are correlated to the electrochemical performances of the composites evaluated using both outer and inner sphere redox molecules. We have shown that both cellulose nanocrystals (CNC) and cellulose nanofibrils (CNF) having different surface functionalizations, can be used to develop highly stable, robust electrochemical platforms with MWCNT, without compromising the electrochemical activity of the MWCNT. The nanocellulose geometry is clearly demonstrated to have a significant effect upon the composite morphology, where the highly functionalized CNFs result in open architectures with more exposed MWCNT surface, and CNCs result in denser architectures with the CNC packed closely around theMWCNT. Correspondingly, the CNF-based composites exhibit higher electrochemically active surface area, increased electrostatic effects and stronger redox currents for all measured analytes. The nature and degree of nanocellulose functionalization is shown to have a significant effect on the extent of electrostatic effects in the composite, offering a promising route towards tailoring the ionic selectivity. Finally, we demonstrate that all the nanocellulose / MWCNT composites proposed in this work are capable of achieving significantly higher sensitivity and selectivity towards a cationic inner sphere redox molecule such as dopamine, compared to current commercial standard MWCNT electrodes.
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    Reliability assessment of electronic assemblies under multiple interacting loading conditions
    (Aalto University, 2013) Karppinen, Juha; Laurila, Tomi, Prof., Aalto University, Finland; Mattila, Toni, Docent, Aalto University, Finland; Elektroniikan laitos; Department of Electronics; Unit of Electronics Integration and Reliability; Sähkötekniikan korkeakoulu; School of Electrical Engineering; Paulasto-Kröckel, Mervi, Prof., Aalto University, Finland
    This dissertation presents the results of multiple experimental and computational reliability assessment methods employed on electronic assemblies. It is demonstrated that the typical standardized test procedures often fail to capture the complex loading conditions of service environment and can lead to artificial results due to excessive damage acceleration. An alternative reliability assessment approach based on the use of combined loading tests derived from product service loading characterization is proposed as a solution to the problem. In this proposed approach special attention is paid to establishing a stronger correlation between the material-scientific reliability analyses and lifetime prediction methods. Several methods on how to predict and characterize the reliability of component assemblies under different use cases and field environments are presented. Particular emphasis is placed on the reliability of board-level solder interconnections due to their complex and often unsatisfactory reliability behavior. It is shown that multiple microstructural mechanisms, such as dispersion strengthening, grain growth, strain rate hardening, fatigue and recrystallization, contribute together to the reliability performance of interconnections. The presented relationships between these mechanisms and the affecting loading conditions enable more accurate and comprehensive assessment of electronic product reliability.