Surface modification of PDMS based microfluidic systems by tensides

The material aspects of a polymer based microfluidic structure were characterised considering the compatibility of the system with bioanalytical applications. The polydimethylsiloxane (PDMS) based channel system is to be integrated in a full polymer photonic biosensor device developed within the European Union project P3SENS (FP7-ICT4-248304). This work is intended to define a modified material composition, which is appropriate to improve both the wettability and the non-specific protein binding characteristics of the PDMS significantly. Triton X-100 (Sigma-Aldrich) surfactant was added to the raw PDMS before polymerisation. The influence of the tenside was studied considering the polymerisation reaction, the surface characteristics and the functional applicability. To test the hydrodynamic behaviour and non-specific protein adsorption on the surfaces, phosphate buffered saline (PBS) solution and fluorescent labelled human serum albumin (HSA) was applied in a microfluidic capillary system. © (2013) Trans Tech Publications, Switzerland

Aktuálási elvek mozgó 3D mikroszerkezetekben = Actuation phenomena in 3D moving microstructures

A modern technológiák a MEMS (mikro elektro-mechanikai) eszközöket széles körben alkalmazzák, és ezen belül is egyre hangsúlyosabb szerepet kapnak az összetett, aktív elemeket is tartalmazó integrált mikrorendszerek. A beavatkozók jellegzetes csoportját alkotják a szabadon álló, megfelelő technikai megoldásokkal kialakított, felfüggesztett 3D alakzatok, amelyek különböző módszerekkel mozgathatóak (pl. mikroáramlási csatornában elhelyezett szelepek, turbinák, mozgatható tükrökből felépülő hálózatok, stb.). Az alapvetően alkalmazott mozgatási technikák mágneses, termikus és elektrosztatikus jelenségeken alapulnak. A kutatás alapvető célja volt, hogy megvizsgáljam a vezérelt mikroméretű eszközökben lejátszódó fizikai folyamatok jellegét, és ennek segítségével tervezhetővé tegyem az egyes szerkezetek funkcionális viselkedését, valamint specifikus kialakítási technológiákat dolgozzak ki különleges 3D struktúrák megvalósítását célozva, beleértve a strukturális anyagok megválasztását is. Ennek érdekében különböző tesztstruktúrákat terveztem és alakítottam ki az MFA MEMS Laboratóriumában, és vizsgáltam ezek működését. Emellett végeselem kód felhasználásával termo-mechanikai, illetve elektro-mechanikai szimulációkat végeztem, amelyek elősegítik a lejátszódó folyamatok könnyebb megértését, és lehetővé teszik a későbbiekben megvalósítandó eszközök működésének tervezését. A modellszámítások és a kísérletek összehasonlítása alapján demonstrációs eszközöket állítottam elő, és ezek működésén keresztül vizsgáltam a mozgó struktúrák mechanikai és funkcionális jellemzőit. | MEMS (micro-electro-mechanical systems) are widely applied in modern technologies. The complex, integrated micro-systems containing active parts play determining role in increasing number of applications. A dominant section of the actuators is constituted by the free standing, suspended 3D structures, which can be actuated, displaced (valves and turbines situated in micro flow channels, arrays of movable-rotating mirrors, etc.). The basic actuation principles are based on magnetic, electrostatic or thermal processes. The ultimate goals of the research were the analysis of the physical phenomena involved in moving microstructures, to support the functional design of the specific devices. Development of specific fabrication technology was also planned for achieving the realisation of special 3D structures including the specification of the possible structural materials. In order to succeed the project’s objective different test-structures were designed, realized and investigated using the infrastructure of the MEMS Laboratory at the Research Institute for Technical Physics and Materials Science. Thermo-mechanical and electro-mechanical simulations were performed – applying finite element modelling – to support the comprehension of the physical processes and to predict the functional properties of the planned devices. On the basis of model calculations and experiments demonstration devices were constructed and their functional and mechanical behaviour were investigated

Effects of Micropatterning and Surface Modification of Microfluidic Channels on Capillary Water Transport

AbstractThis work is intended to characterize the fluid conducting behaviour of microcapillary systems containing various 3D microstructures and surface modifying molecular layers. The microchannels are patterned by secondary structures mimicking the natural water-conducting tissue (xylem) of dry-habitat plants. The complex microstructure of the microcapillary system was developed by bulk silicon micromachining technology, applying multistep Deep Reactive Ion Etching (DRIE) to fabricate and pattern the microfluidic channels subsequently. The inner surfaces of the capillary systems were covered by Atomic Layer Deposition (ALD) of different oxide layers to control their wetting properties. We demonstrated that the fluid conducting behaviour of the fabricated capillary systems can be systematically controlled by structural patterning and surface modification of the channels

Félvezető szenzorok elektronikus zajának eredete = The origin of electronic noise in semiconductor sensors

A projekt támogatásának felhasználásával létrehoztunk egy alacsonyfrekvenciás zaj mérésére alkalmas laboratóriumot. A fő műszer az SR785 spektrum analizátor. Szenzor anyagok és szenzorok zajtulajdonságait vizsgáltuk. A zajmérések segítségével értelmeztük a porózus Si áramvezetési mechanizmusát. Zaj szempontból optimalizáltuk az PbS fotóellenállás technológiáját. Megállapítottuk, hogy az ion-implantantált piezo-ellenállások zaja kritikusan függ az ellenállás-hordozó közti p-n átmenet záróirányú áramától. Vizsgáltuk a szenzorok zaja miatti elvi alkalmazási korlátozásokat. Rendszeresen szerepeltünk a Fluctuation and Noise Symposium-on. Számos fiatal kutatót és gyakornokot vontunk be a munkákba. | Low-frequency electrical noise measuring set up has been built due to the financial support of the project. The main instrument is the SR785 dual channel dynamic signal analyser. The noise characteristics of sensors and sensor materials were investigated. The current conduction mechanisms in porous Si were interpreted taking into account the noise. The technology of PbS photo resistor was optimised in respect the noise. It was pointed out that the noise in ion-implanted pieso-resistor depends critically on the reverse current of the p-n junction between the resistor and the substrate. The noise limitations of the figures of merits of sensors were also investigated. Papers were presented in each year on the Fluctuation and Noise Symposium. Numerous young scientists and trainees were involved in the work

Controlled Focused Ion Beam Milling of Composite Solid State Nanopore Arrays for Molecule Sensing

Various nanoscale fabrication techniques are elaborated to form artificial nanoporous/nanochannel membranes to be applied for biosensing: one of the most prevalent is the micro-electromechanical systems (MEMS) compatible focused ion beam (FIB) milling. This technique can be easily adopted in micro- and nanomachining process sequences to develop composite multi-pore structures, although its precision and reproducibility are key points in the case of these thick multi-layered membranes. This work is to demonstrate a comprehensive characterisation of FIB milling to improve the reliability of the fabrication of solid state nanopore arrays with precisely predetermined pore geometries for a targeted molecule type to be recognised. The statistical geometric features of the fabricated nanopores were recorded as the function of the process parameters, and the resulting geometries were analysed in detail by high resolution scanning electron microscope (SEM), transmission electron microscope (TEM) and ion scanning microscopy. Continuous function of the pore diameter evolution rate was derived from the experimental results in the case of different material structures, and compared to former dissentient estimations. The additional metal layer was deposited onto the backside of the membrane and grounded during the ion milling to prevent the electrical charging of dielectric layers. The study proved that the conformity of the pore geometry and the reliability of their fabrication could be improved significantly. The applicability of the developed nanopore arrays for molecule detection was also considered by characterising the pore diameter dependent sensitivity of the membrane impedance modulation based measurement method

Kémiailag módosított nanopórus alapú érzékelők biomolekuláris kölcsönhatások tanulmányozására = Chemically modified synthetic nanopores for label-free detection of biomolecular interactions

A pályázat elsődleges célkitűzése a nanopórusok analitikai alkalmazásainak vizsgálata volt. Három platformot állítottunk elő és alkalmaztunk érzékelésre: arany nanopórusos membránokat, nanopipettákat, illetve 3D MEMS technológia és fókuszált ionnyaláb marással készült membránokat. Megoldottuk a nanopórusok kémiai módosítását szintetikus receptorokkal: peptid-nukleinsavakkal és originális aptamerekkel. Érzékelőket fejlesztettünk ki fehérjék, DNS szálak meghatározására, és nanorészecskék számlálására. Új aptamereket fejlesztettünk ki az alma törzsgöndörödés vírus meghatározására, amellyel sikerült a vírust közvetlenül növényi extraktumokban kimutatni. Elsőként sikerült szelektív szilárdtest ioncsatornákat előállítani, amelyek a biológiai ioncsatornákat meghaladó több mint hat nagyságrendnyi szelektivitással rendelkeztek. Szilárdtest ioncsatornákon alapuló nanomólos kimutatási határú potenciometriás ezüstion érzékelőket fejlesztettünk ki. Fehérje módosított pórusokat reaktorként alkalmazva polimer rudakat állítottunk elő, amelyek a felületükön szelektív kötőhelyekkel rendelkeznek a pórust módosító fehérjékre. Numerikus módszerekkel és durva szemcsézettségű molekuladinamikai számításokkal meghatároztuk a célkomponens átlagos pórushoz jutási idejének koncentráció függését, a nanopórusok felületi töltéssűrűségét, illetve a nanopórusosban fellépő nanofluidikai effektusokat. A pályázat támogatásával 1 könyvfejezet és 28 közlemény született, amelyek összesített impakt faktorja 134,3. | The primary objective of the project was to explore new aspects of nanopore sensing. Three different nanopore platforms were prepared applied for sensing: gold nanoporous membranes, nanopipepettes and nanoporous membranes made by combining 3D MEMS technology and focused ion beam milling. Methods for chemical modification of nanopores with synthetic receptors, i.e., peptide nucleic acids and original aptamers, were developed. Based on this we have introduced sensors for proteins, DNA strands, and for nanoparticle counting. New aptamers were selected for the determination of apple stem pitting virus, which could detect the virus directly in plant extracts. Selective solid-state ion channels with selectivities exceeding that of the biological ion channels, i.e., more than six orders of magnitude, were introduced for the first time. They formed the base for potentiometric silver sensors with nanomolar detection limit. Reactors using protein modified pores were implemented to generate surface imprinted polymer rods able to selectively recognize the template protein. Numerical methods and coarse grain molecular dynamics were implemented to determine the encounter time of the analyte and nanopore, the surface charge density of nanopores and to interprete nanofluidic effects in the nanopores. One book chapter and 28 scientific papers having a cumulated impact factor of 134.3 were published with the support of the project

Hierarchically Combined Periodic SERS Active 3D Micro- and Nanostructures for High Sensitive Molecular Analysis

To increase the local field intensity of Raman scattering, gold nanospheres were entrapped in gold coated periodic inverse pyramid structures, being SERS substrates by themselves. The applicability of this complex structure for sensitive molecule detection was proved by comparison of the detected Raman signals with and without particle entrapment. Moreover its relevance in molecular diagnostic was also proposed considering the specific surface functionalisation of the gold nanoparticles

Millimeter wave detection by thermopile antenna

AbstractIn this paper a novel MEMS thermopile structure is proposed, which consist of linearly arranged p- and n- type polysilicon strips instead of the conventional loop-like configuration. It is shown that these devices sense the millimeter wave radiation beyond the infrared. The polarity and frequency dependence of the sensitivity prove that these strips behave as absorbing antennas towards the microwave/millimeter wave radiation. The induced current is calculated having a maximum in the geometrical center of the antenna, exactly at the position where the hot end of the thermopair is located. The measured responsitivities to direct heating, infrared radiation, 13 GHz microwave radiation and 100 GHz millimeter-wave radiation are presented

Nanoparticle displacement assay with electrochemical nanopore-based sensors

The proof of concept of a nanoparticle displacement assay that enables the use of large diameter nanopores for the detection of targets of smaller molecular dimensions is presented. We hypothesized that an inherent signal amplification should arise from the selective displacement of nanoparticles preloaded in a nanopore by a much smaller molecular target. The method is demonstrated using peptide nucleic acid (PNA)-functionalized gold nanopore arrays in which short DNA-modified gold nanoparticles are anchored by weak interaction. Complementary microRNAs are detected via the resistance change caused by competitive displacement of nanoparticles from the PNA-functionalized nanopores