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Kämpfer Alexandra

Professeur-e HES associé-e

Main skills

Professeur-e HES associé-e

Phone: +41 32 930 25 53

Haute Ecole Arc - Ingénierie
Espace de l'Europe 11, 2000 Neuchâtel, CH

BSc HES-SO en Industrial Design Engineering - Haute Ecole Arc - Ingénierie

Procédés de micro-fabrication
Procédés de micro-fabrication et applications
BioMEMS et microfluidique
Biophysique

Ongoing

AOP Plug and play

Role: Co-applicant

Financement: Bridge Discovery

Description du projet :

Réalisation en mode industriel de puces de microfluidique.

Research team within HES-SO: Kämpfer Alexandra , Roth Joy , Flahaut Frédéric , Laux Edith , Jeandupeux Laure , Wenger Samuel

Durée du projet: 01.07.2020 - 30.06.2024

Statut: Ongoing

ComplexFluidPrint

Role: Co-applicant

Financement: HES-SO

Description du projet :

Développment d'une nouvelle tête d'impression jet d'encre pour l'impression de fluides complexes.

Research team within HES-SO: Balestra Gioele , Domae Yoshinori , Maturo Jonas , Kämpfer Alexandra , Laux Edith , Manimala Ajith

Durée du projet: 01.12.2019

Statut: Ongoing

Completed

Une nouvelle génération de sensors pour la détection du phosgène (PhoSensor)

Role: Collaborator

Financement: HES-SO

Description du projet :

Phosgene (COCl2) is a highly poisonous chemical weapon agent (CWA). Unlike other CWA whose production and use are internationally prohibited, several million tons of phosgene are produced all over the world each year because this compound is a valuable building block for the synthesis of various plastics, pesticides and pharmaceuticals. This represents a huge threat to public health and safety not only because of possible accidental leaking but also because of potential terrorist attacks. Thus, is of great importance to develop highly sensitive and selective sensors for phosgene in gas but also in liquid phase.
A number of phosgene sensors based on diamine or alcohol type sensing molecules are available but most of them have important limitations in terms of portability, selectivity, detection limit, costs and / or lifetime.
Recently, we discovered in a totally serendipitous manner, that a new compound, a carboxylic derivative of a chiral pinenepyridine compound (1 in the project description) reacts with traces of phosgene present accidentally in a sample. The resulting isoindolone type molecule is colored and luminescent. Some preliminary investigations were performed under the guidance of the internationally recognized Swiss institute for the protection of the population against nuclear, biological and chemical threats and dangers, known also as Spiez Laboratory, who provides worldwide services relating to arms control, protection measures, health and incident management. These investigations have shown very promising results: stable sensing molecule, very rapid sensing reaction, high selectivity, very low detection limit.
In the framework of this project we propose to investigate the use of a completely new sensing type reaction, never reported in literature, in order to develop a fluorescent / colorimetric portable sensor for phosgene and phosgene related products.
The chemists from HEIA will design and synthesize a library of compounds structurally related to parent compound 1. In the environmental conditions the sensor is expected to operate, these molecules will be benchmarked in terms of stability, selectivity, detection limit and cost projections. The best candidates will be selected and their synthetic route optimized.
Programme de recherche / Appel à projets 2021 2/24
The engineers from HE Arc will built up the appropriate sensor prototype as a portable device, in agreement with the requirements of the sensing system. Using their proven skills in microfluidics, microelectronics and sensors integration, they will start by encapsulating the sensing molecule in a high surface area material (made by electrospinning). Readout on the portable device will be done:
a) qualitatively by a change in color/fluorescence of the sensor fabric and
b) quantitatively by a compact optical readout made of a LED/filter/photodiode cost-effective setup.
The HES-SO consortium will work in close collaboration with the Spiez Laboratory who will test the sensing molecules (in the WP2) but also the sensor prototype (WP5) and help to establish contacts with potential interested end users from industry for commercial exploitation. Moreover, other very dangerous, phosgene related molecules to which only this specialized laboratory has access, molecules chemically compatible with the new sensing system proposed here, will be tested in Spiez.

Research team within HES-SO: Jeandupeux Laure , Mamula Steiner Olimpia , Kämpfer Alexandra , Laux Edith

Durée du projet: 01.12.2021 - 30.06.2023

Statut: Completed

Food quality, Antioxidant assays, HPLC, Microfluidics, MeV ion beam lithography, track and trace

AGP

Role: Main Applicant

Financement: HES-SO Rectorat

Description du projet : The project's objective is to combine both approaches into a system that for one sample injection fingerprints the bioactive compounds and assesses the antioxidant activities of individual compounds at the same time. This is done by a plug-in device that can be fitted to different HPLC instruments or stand-alone with FIA systems. The device is based on a microfluidic chip that splits the HPLC eluent stream between three anti-oxidant analysis modules operating in parallel with conventional UV/Vis fluorescence detector. Two modules will assay antiradical scavenging activity (DPPH' and ABTS'+ (TEAC assay)) and the third total antioxidant capacity (ferric reducing antioxidant power FRAP). The results enable assessment of the compounds responsible for the antioxidant capacity of analysed food sample. This knowledge helps to select the most promising marker compounds for tracing antioxidant evolution from farm to fork through the food chain.

Research team within HES-SO: Farine Brunner Sophie , Andlauer Wilfried , Kämpfer Alexandra , Geiser Martial , Broggini Christiane , Cséfalvay Catherine , Prieur Claudio , Ramseyer Stephan , Bisoffi Fabrice , Udrisard Isabelle , Truffer Frédéric , Hochstrasser Eric , Jeandupeux Laure

Partenaires académiques: VS - Institut Systèmes industriels; VS - Institut Sciences du vivant; Micro et nano systèmes; Kämpfer-Homsy Alexandra, Micro et nano systèmes

Durée du projet: 01.12.2016 - 30.11.2018

Montant global du projet: 164'950 CHF

Statut: Completed

Intégration d'un capteur permettant le suivi en continu de substances thérapeutiques dans le sang - Diagnostic Biochips - Projet DB-2015-003

AGP

Role: Co-applicant

Requérant(e)s: VS - Institut Systèmes industriels, Roduit Pierre, VS - Institut Systèmes industriels

Financement: HES-SO Rectorat

Description du projet : Lors de traitements médicamenteux à l'hôpital tels que les chimiothérapies ou les anesthésies, les patients sont soumis à des doses très élevées de la substance thérapeutique pendant de longues durées qui peuvent aller jusqu'à plusieurs jours lors de cancers. Les concentrations du médicament dans le sang peuvent alors considérablement varier et atteindre des niveaux entraînant des effets secondaires importants voire fatals. Idéalement, les doses de médicament devraient être continuellement adaptées pour éviter ces pics et ainsi fortement atténuer les effets secondaires, mais ceci nécessiterait des analyses sanguines régulières (typ. tous les 5-15 minutes), ce qui n'est actuellement pas possible pour des raisons logistiques. Un système de mesure continu rendrait possible un tel suivi avec la possibilité d'éventuellement corriger le dosage de manière automatique. Dans le cadre du projet SupraDiag, des bio-senseurs supramoléculaires sont en cours de développement dont la fluorescence est modulée par la présence de substances actives de chimiothérapies. L'objectif de ce nouveau projet est d'intégrer cette technologie dans un démonstrateur permettant de faire le suivi quantitatif de médicaments directement dans le sang. Ce projet extrêmement interdisciplinaire aura pour but de régler tous les problèmes importants qu'il reste à résoudre pour avoir un démonstrateur portable: - Développement d'un système micro-fluidique pour le prélèvement et le transfert de l'échantillon vers une micro-chambre contenant les bio-senseurs et pour le lavage de celle-ci après la mesure, - Adaptation des bio-senseurs supramoléculaires aux mesures en continu dans le sang, - Insertion des bio-senseurs dans des hydrogels protecteurs permettant de ne laisser diffuser que les petites molécules, - Conception de revêtements anti-biofouling, - Développement de l'optique intégrée qui permettra de mesure le taux de fluorescence émise par les bio-senseurs, - Développement de l'électronique de contrôle et de mesure, - Développement de la partie communication sans fils qui permettra d'exporter la valeur mesurée du capteur. Ce projet pourra profiter des technologies développées dans le cadre du programme durant les projets SmartH2OGel (hydrogels), SupraDiag (bio-senseurs supramoléculaires) et MiniBioDet (modification de surfaces). L'appareil de suivi de substances thérapeutiques développé dans ce projet sera le démonstrateur prototypique d'une nouvelle génération d'instruments de médecine personnalisée.

, , , , , , , , , , , , , , , , , , Research team within HES-SO: Walpen Olivier Aellen Thierry Farine Brunner Sophie Kämpfer Alexandra Condemi Enrico Geiser Martial Broggini Christiane Cséfalvay Catherine Prieur Claudio Truffer Frédéric Hochstrasser Eric Simalatsar Alena Marti Roger Segura Jean-Manuel Laux Edith Jeandupeux Laure Pfeifer Marc Emil Roduit Pierre Jacquemettaz Pascal

Partenaires académiques: VS - Institut Systèmes industriels; Microtechnologies appl.; VS - Institut Sciences du vivant; FR - EIA - Institut ChemTech; Roduit Pierre, VS - Institut Systèmes industriels

Durée du projet: 01.01.2016 - 31.12.2017

Montant global du projet: 250'000 CHF

Statut: Completed

2020

Impact of organic solvents in combination with redox-couples on magnitude of seebeck coefficient, and electrical current in thermoelectric generators

Scientific paper ArODES

Edith Laux, Laure Jeandupeux, Alexandra Kämpfer, Martin Hofmann, Philippe Potty, Herbert Keppner

Materials Today: Proceedings, 2021, 44, 4, 3489-3493

Link to the publication

Summary:

In previous work it was shown that Ionic Liquids as active substances in thermoelectric generators have the potential to reduce the thermal conductivity as compared to Solid State materials used in conventional TEGs. Furthermore, it was observed that the Seebeck coefficient could be significantly increased. After a large variety of experiments, it appears that the remaining bottleneck coming to high performance TEGs is, first finding ILs with increased negative Seebeck coefficient, and, second sufficient current extraction. Looking at the current it appears, that higher extractions for a given redox-couple concentration are favoured at reduced viscosity. On the way to explore the effect of viscosity-induced current limitation, in a first step, the Ionic liquids are substituted by a low-viscosity organic solvent such as propylene carbonate (PC). The results showed that, indeed, the thermo-current increases significantly. It was further found that the Seebeck coefficient (SE) using PC exhibited values as high as 1.7 mV/K. Such high values were in previous work rather attributed to the use of ionic liquids. Surprisingly, by adding up to 10% of water to PC, the increased current allowed doubling the power, compared to pure PC. The paper studies the effect of combinations of solvent and redox-couples and tries to correlate the effect of water in PC looking at physical properties such as viscosity, but also the effects of charged carrier-attachment at the electrodes.

2017

Fabrication of high-transmission microporous membranes by proton beam writing-based molding technique

Scientific paper ArODES

Liping Wang, Clemens Meyer, Edouard Guibert, Alexandra Kämpfer, Harry J. Whitlow

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2017, vol. 404, pp. 224-227

Link to the publication

Summary:

Porous membranes are widely used as filters in a broad range of micro and nanofluidic applications, e.g. organelle sorters, permeable cell growth substrates, and plasma filtration. Conventional silicon fabrication approaches are not suitable for microporous membranes due to the low mechanical stability of thin film substrates. Other techniques like ion track etching are limited to the production of randomly distributed and randomly orientated pores with non-uniform pore sizes. In this project, we developed a procedure for fabricating high-transmission microporous membranes by proton beam writing (PBW) with a combination of spin-casting and soft lithography. In this approach, focused 2 MeV protons were used to lithographically write patterns consisting of hexagonal arrays of high-density pillars of few µm size in a SU-8 layer coated on a silicon wafer. After development, the pillars were conformably coated with a thin film of poly-para-xylylene (Parylene)-C release agent and spin-coated with polydimethylsiloxane (PDMS). To facilitate demolding, a special technique based on the use of a laser-cut sealing tape ring was developed. This method facilitated the successful delamination of 20-μm thick PDMS membrane with high-density micropores from the mold without rupture or damage.

2016

Red blood cell phase separation in symmetric and asymmetric microchannel networks :

Scientific paper ArODES

effect of capillary dilation and inflow velocity

Francesco Clavica, Alexandra Kämpfer, Laure Jeandupeux, Dominik Obrist

Scientific reports, 2016, article no. 36763

Link to the publication

Summary:

The non-uniform partitioning or phase separation of red blood cells (RBCs) at a diverging bifurcation of a microvascular network is responsible for RBC heterogeneity within the network. The mechanisms controlling RBC heterogeneity are not yet fully understood and there is a need to improve the basic understanding of the phase separation phenomenon. In this context, in vitro experiments can fill the gap between existing in vivo and in silico models as they provide better controllability than in vivo experiments without mathematical idealizations or simplifications inherent to in silico models. In this study, we fabricated simple models of symmetric/asymmetric microvascular networks; we provided quantitative data on the RBC velocity, line density and flux in the daughter branches. In general our results confirmed the tendency of RBCs to enter the daughter branch with higher flow rate (Zweifach-Fung effect); in some cases even inversion of the Zweifach-Fung effect was observed. We showed for the first time a reduction of the Zweifach-Fung effect with increasing flow rate. Moreover capillary dilation was shown to cause an increase of RBC line density and RBC residence time within the dilated capillary underlining the possible role of pericytes in regulating the oxygen supply.

2015

Fabrication and characterization of a test platform integrating nanoporous structures with biochemical functionality

Scientific paper ArODES

Karen Twomey, Paul O'Mara, Jaroslaw Pulka, Shane McGillycuddy, Eileen Hurley, Allan Blake, Patricia Vazquez, Elizaveta Vereshchagina, Mary Manning, Alexandra Kämpfer, Barry Glynn, Vladimir I. Ogurtsov

IEEE Sensors Journal, 2015, vol. 15, no. 8, pp. 4329-4337

Link to the publication

Summary:

The application of solid-state nanopore technology for biosensing is a rapidly developing area of research with high commercial potential. Different synthetic materials, including silicon nitride, alumina, and polymers, are employed to fabricate single and multiple pores and offer a good platform for selective biomolecule detection. Two solid-state pore arrays, one with integrated silicon microfluidic system, were considered and an immobilization strategy suitable for detecting a single-stranded DNA (ssDNA) sequence was investigated. For the silicon nitride pores, a modification method based on the use of 3-aminopropyltriethoxysilane for silanization and 1,4-phenylene diisothiocyanate for amine crosslinking was applied to immobilize 100-nM ssDNA (amine C6) and a 100-nM limit of detection for complementary to probe ssDNA (Cy5) was estimated. The polycarbonate pores (the second type of the pore arrays) underwent surface modification based on an oxidation reduction reaction using sodium periodate and sodium borohydride and was used to immobilize 10-nM ssDNA and an estimated 100-nM limit of detection was also achieved. Linear sweep voltammetry was used to characterize the pores and a current potential profile was obtained after both immobilization of probe ssDNA and hybridization of complementary to probe ssDNA on the modified pore array surface. A decrease in current amplitude was measured after surface modification of both pore arrays, and this was attributed to the appearance of an additional layer on the pore surface reducing the pore opening and hindering the current flow. The hybridization event was also supported by contact angle measurements, where an increase in hydrophilicity was recorded at the different surface modification steps that were applied to produce the biofunctionalized nanopore. In addition, fluorescence was observed on the surfaces after hybridization, through incorporation of a CY5 fluorescent tag attached on the 5' end of the complementary to probe DNA. These results show the potential to use both silicon nitride and polycarbonate nanopores in DNA detection applications.

MeV ion beam lithography of biocompatible halogenated parylenes using aperture masks

Scientific paper ArODES

Harry J. Whitlow, Rattanaporn Norarat, Marta Roccio, Patrick Jeanneret, Edouard Guibert, Maxime Bergamin, Gianni Fiorucci, Alexandra Kämpfer, Edith Laux, Herbert Keppner, Pascal Senn

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2015, vol. 354, pp. 34-36

Link to the publication

Summary:

Parylenes are poly(p-xylylene) polymers that are widely used as moisture barriers and in biomedicine because of their good biocompatibility. We have investigated MeV ion beam lithography using 16O+ ions for writing defined patterns in Parylene-C, which is evaluated as a coating material for the Cochlear Implant (CI) electrode array, a neuroprosthesis to treat some forms of deafness. Parylene-C and -F on silicon and glass substrates as well as 50 μm thick PTFE were irradiated to different fluences (1 x 1013 - 1 x 1016 1 MeV16O+ ions cm−2) through aperture masks under high vacuum and a low pressure (<10−3 mbar) oxygen atmosphere. Biocompatibility of the irradiated and unirradiated surfaces was tested by cell-counting to determine the proliferation of murine spiral ganglion cells. The results reveal that an oxygen ion beam can be used to pattern Parylene-C and -F without using a liquid solvent developer in a similar manner to PTFE but with a ∼25× smaller removal rate. Biocompatibility tests showed no difference in cell adhesion between irradiated and unirradiated areas or ion fluence dependence. Coating the Parylene surface with an adhesion-promoting protein mixture had a much greater effect on cell proliferation.

Solid on liquid deposition, a review of technological solutions

Scientific paper ArODES

Alexandra Kämpfer, Edith Laux, Laure Jeandupeux, Jerome Charmet, Roland Bitterli, Chiara Botta, Yves Rebetez, Oksana Banakh, Herbert Keppner

Microelectronic Engineering, 2014, vol. 14, pp. 467-279

Link to the publication

Summary:

Solid-on-liquid deposition (SOLID) techniques are of great interest to the MEMS and NEMS (Micro- and Nano Electro Mechanical Systems) community because of potential applications in biomedical engineering, on-chip liquid trapping, tunable micro-lenses, and replacements of gate oxides. However, depositing solids on liquid with subsequent hermetic sealing is difficult because liquids tend to have a lower density than solids. Furthermore, current systems seen in nature lack thermal, mechanical or chemical stability. Therefore, it is not surprising that liquids are not ubiquitous as functional layers in MEMS and NEMS. However, SOLID techniques have the potential to be harnessed and controlled for such systems because the gravitational force is negligible compared to surface tension, and therefore, the solid molecular precursors that typically condense on a liquid surface will not sediment into the fluid. In this review we summarize recent research into SOLID, where nucleation and subsequent cross-linking of solid precursors results in thin film growth on a liquid substrate. We describe a large variety of thin film deposition techniques such as thermal evaporation, sputtering, plasma enhanced chemical vapor deposition used to coat liquid substrates. Surprisingly, all attempts at deposition to date have been successful and a stable solid layer on a liquid can always be detected. However, all layers grown by non-equilibrium deposition processes showed a strong presence of wrinkles, presumably due to residual stress. In fact, the only example where no stress was observed is the deposition of parylene layers (poly-para-xylylene, PPX). Using all the experimental data analyzed to date we have been able to propose a simple model that predicts that the surface property of liquids at molecular level is influenced by cohesion forces between the liquid molecules. Finally, we conclude that the condensation of precursors from the gas phase is rather the rule and not the exception for SOLID techniques.

2014

Mid-infrared spectroscopy for gases and liquids based on quantum cascade technologies

Scientific paper ArODES

Pierre Jouy, Markus Mangold, Béla Tuzson, Lukas Emmenegger, Yu-Chin Chang, Lubos Hvozdara, Hans Peter Herzig, Philip Wägli, Alexandra Kämpfer, Nico F. de Rooij, Alexander Wirthmueller, Daniel Hofstetter, Herbert Looser, Jérôme Faist

The Analyst, 2014, vol. 139, no. 9, pp. 2039-2046

Link to the publication

Summary:

In this paper we present two compact, quantum cascade laser absorption spectroscopy based, sensors developed for trace substance detection in gases and liquids. The gas sensor, in its most integrated version, represents the first system combining a quantum cascade laser and a quantum cascade detector. Furthermore, it uses a toroidal mirror cell with a volume of only 40 cm(3) for a path length of up to 4 m. The analytical performance is assessed by the measurements of isotope ratios of CO2 at ambient abundance. For the (13)CO2/(12)CO2 isotope ratio, a measurement precision of 0.2‰ is demonstrated after an integration time of 600 s. For the liquid sensor, a microfluidic system is used to extract cocaine from saliva into a solvent (PCE) transparent in the mid-infrared. This system is bonded on top of a Si/Ge waveguide and the concentration of cocaine in PCE is measured through the interaction of the evanescent part of the waveguide optical mode and the solvent flowing on top. A detection limit of <100 μg mL(-1) was achieved with this system and down to 10 μg mL(-1) with a simplified, but improved system.

2013

Microfluidic droplet-based liquid–liquid extraction and on-chip IR spectroscopy detection of cocaine in human saliva

Scientific paper ArODES

Philip Wägli, Yu-Chi Chang, Alexandra Kämpfer, Lubos Hvozdara, Hans Peter Herzig, Nico F. de Rooij

Analytical Chemistry, 2013, vol. 85, no. 15, pp. 7558-7565

Link to the publication

Summary:

We present a portable microsystem to quantitatively detect cocaine in human saliva. In this system, we combine a microfluidic-based multiphase liquid–liquid extraction method to transfer cocaine continuously from IR-light-absorbing saliva to an IR-transparent solvent (tetrachloroethylene) with waveguide IR spectroscopy (QC-laser, waveguide, detector) to detect the cocaine on-chip. For the fabrication of the low-cost polymer microfluidic chips a simple rapid prototyping technique based on Scotch-tape masters was further developed and applied. To perform the droplet-based liquid–liquid extraction, we designed and integrated a simple and robust droplet generation method based on the capillary focusing effect within the device. Compared to well-characterized and commonly used microfluidic H-filters, our system showed at least two times higher extraction efficiencies with potential for further improvements. The current liquid–liquid extraction method alone can efficiently extract cocaine and pre-concentrate the analytes in a new solvent. Our fully integrated optofluidic system successfully detected cocaine in real saliva samples spiked with the drug (500 μg/mL) and allowed real time measurements, which makes this approach suitable for point-of-care applications.

2022

Production and viability of encapsulated bacterial-fungal consortia for delivery in soil

Conference ArODES

Alexandra Kämpfer, Edith Laux, Laure Jeandupeux, T. Nogueira-Matos, A. Manimala, Nina Châtelain, Claudio Prieur, Cristina Martin-Olmos, Isha Hashmi, C. Hyde, C. Ruiz, Pilar Junier, Saskia Bindschedler

Proceedings of 26th International Conference on Miniaturized Systems for Chemistry and Life Sciences, 23-27 October 2022, Hangzhou, China

Link to the conference

Summary:

In this study, we present a novel type of microfluidics-based formulation for the delivery of microbial control agents (mBCAs) in soil, where bacterial cells and fungal spores are directly combined into millimeter-sized alginate capsules. This process resulted in the reproducible production of 500 μm sized beads in a good throughput for this type of biofluid (up to 48 beads/min). A subsequent chitosan coating (1-2 μm-thick) provided a good storage stability at 3 months, with 100% microcapsules containing viable fungal biomass and 60-80% with viable bacterial cells depending on the species. This novel formulation was tested both in the greenhouse and on-farm with lettuces, and encapsulated microbial biomass had a more prominent effect on crop growth and yield, as compared to their delivery as a liquid suspension.

2015

Blood cell dynamics in a simple model of microvascular networks

Conference ArODES

Francesco Clavica, Alexandra Kämpfer, Laure Jeandupeux, Herbert Keppner, Dominik Obrist

Proceedings of 19th International Conference on Miniaturized Systems for Chemistry and Life Sciences, 25-29 October 2015, Gyeongju, South Korea

Link to the conference

Summary:

The dynamic distribution of red blood cells (RBCs) plays a crucial role in cerebral oxygenation, metabolism and many brain disorders (e.g. Alzheimer, ischemic stroke). Despite the growing number of studies on blood rheology in microcirculation, there remains still a big need for detailed experimental data on RBCs distribution in network of microchannels. To our best knowledge, this is the first experimental study of blood cell dynamics in simple networks of microchannels (height less than 10µm) under well controlled conditions which allows a systematic understanding of effects caused by single blood cells.

Achievements

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Directory and Skills inventory

Kämpfer Alexandra

Professeur-e HES associé-e

Main skills

Microfabrication

Microfluidics

Packaging

Micropumps

Bonding

Professeur-e HES associé-e

PEOPLE@HES-SO Directory and Skills inventory

Kämpfer Alexandra

Professeur-e HES associé-e

Main skills

Microfabrication

Microfluidics

Packaging

Micropumps

Bonding

Professeur-e HES associé-e

PEOPLE@HES-SO
Directory and Skills inventory