25 research outputs found
Low power silicon-based thermal sensors and actuators for chemical applications
In the Hot Silicon project low and ultra-low-power Si-based hot surface devices have been developed, i.e. thermal sensors and actuators, for application in catalytic gas micro sensors, micro- and nano- calorimeters.\ud
This work include several scientific and technological aspects:\ud
⢠Design and fabrication of suspended membrane ultra-low-power hot-surface Si-based thermal sensors and actuators;\ud
⢠Integration of the sensors and actuators into a micro flow channel, and investigation of the related microfluidic aspects, i.e. flow behavior and control, heat transport and transport of reactive species,\ud
⢠Investigation of potential applications in the field of micro calorimetric sensing, e.g. studying thermallyactivated physical and chemical processes on-a-chip, i.e. detection of reaction heats, adsorption/desorption kinetics
Special Issue on âAdvances in Microfluidics Technology for Diagnostics and Detectionâ
In recent years microfluidics and lab-on-a-chip havecome to the forefront in diagnostics and detection [...
A hybrid microfluidic platform for cell-based assays via diffusive and convective trans-membrane perfusion
We present a novel 3D hybrid assembly of a polymer microfluidic chip with polycarbonate track-etched membrane (PCTEM) enabling membrane-supported cell culture. Two chip designs have been developed to establish either diffusive or
convective reagent delivery using the integrated PCTEM. While it is well suited to a range of cell-based assays, we specifically employ this platform for the screening of a common antitumor chemotoxic agent (mitomycin C â MMC) on the HL60 myeloid leukemia cell line. The toxic activity of MMC is based on the generation of severe DNA damage in the cells. Using either mode of operation, the HL60 cells were cultured on-chip before, during, and after exposure to MMC at concentrations ranging from 0 to 50 lM. Cell viability was analysed off-chip by the trypan blue dye exclusion assay. The results of the on-chip viability assay were found to be consistent with those obtained off-chip and indicated ca. 40% cell survival at MMC concentration of 50 lM. The catalogue of capabilities of the here described cell assay
platform comprises of (i) the culturing of cells either under shear-free conditions or under induced through-membrane flows, (ii) the tight time control of the reagent
exposure, (iii) the straightforward assembly of devices, (iv) the flexibility on the choice of the membrane, and, prospectively, (v) the amenability for large-scale parallelization
Application of Polymethylpentene, an Oxygen Permeable Thermoplastic, for Long-Term on-a-Chip Cell Culture and Organ-on-a-Chip Devices
The applicability of a gas-permeable, thermoplastic material polymethylpentene (PMP) was investigated, experimentally and analytically, for organ-on-a-chip (OoC) and long-term on-a-chip cell cultivation applications. Using a sealed culture chamber device fitted with oxygen sensors, we tested and compared PMP to commonly used glass and polydimethylsiloxane (PDMS). We show that PMP and PDMS have comparable performance for oxygen supply during 4 days culture of epithelial (A549) cells with oxygen concentration stabilizing at 16%, compared with glass control where it decreases to 3%. For the first time, transmission light images of cells growing on PMP were obtained, demonstrating that the optical properties of PMP are suitable for non-fluorescent, live cell imaging. Following the combined transmission light imaging and calcein-AM staining, cell adherence, proliferation, morphology, and viability of A549 cells were shown to be similar on PMP and glass coated with poly-L-lysine. In contrast to PDMS, we demonstrate that a film of PMP as thin as 0.125 mm is compatible with high-resolution confocal microscopy due to its excellent optical properties and mechanical stiffness. PMP was also found to be fully compatible with device sterilization, cell fixation, cell permeabilization and fluorescent staining. We envision this material to extend the range of possible microfluidic applications beyond the current state-of-the-art, due to its beneficial physical properties and suitability for prototyping by different methods. The integrated device and measurement methodology demonstrated in this work are transferrable to other cell-based studies and life-sciences applications.publishedVersio
Prototyping in Polymethylpentene to Enable Oxygen-Permeable On-a-Chip Cell Culture and Organ-on-a-Chip Devices Suitable for Microscopy
With the rapid development and commercial interest in the organ-on-a-chip (OoC) field, there is a need for materials addressing key experimental demands and enabling both prototyping and large-scale production. Here, we utilized the gas-permeable, thermoplastic material polymethylpentene (PMP). Three methods were tested to prototype transparent PMP films suitable for transmission light microscopy: hot-press molding, extrusion, and polishing of a commercial, hazy extruded film. The transparent films (thickness 20, 125, 133, 356, and 653 Âľm) were assembled as the cell-adhering layer in sealed culture chamber devices, to assess resulting oxygen concentration after 4 days of A549 cell culture (cancerous lung epithelial cells). Oxygen concentrations stabilized between 15.6% and 11.6%, where the thicker the film, the lower the oxygen concentration. Cell adherence, proliferation, and viability were comparable to glass for all PMP films (coated with poly-L-lysine), and transparency was adequate for transmission light microscopy of adherent cells. Hot-press molding was concluded as the preferred film prototyping method, due to excellent and reproducible film transparency, the possibility to easily vary film thickness, and the equipment being commonly available. The molecular orientation in the PMP films was characterized by IR dichroism. As expected, the extruded films showed clear orientation, but a novel result was that hot-press molding may also induce some orientation. It has been reported that orientation affects the permeability, but with the films in this study, we conclude that the orientation is not a critical factor. With the obtained results, we find it likely that OoC models with relevant in vivo oxygen concentrations may be facilitated by PMP. Combined with established large-scale production methods for thermoplastics, we foresee a useful role for PMP within the OoC field.publishedVersio
Local deposition and patterning of catalytic thin films in microsystems
The local deposition of catalysts is desired in a wide range of catalytic microsystems (microreactors and sensors). In this study, we investigate technologies enabling deposition and patterning of catalyst thin films in a manner compatible with standard micromachining processes. We evaluate and compare deposition techniques based on a combination of a self-assembly, soft-lithography and conventional micromachining. Platinum (Pt) and palladium (Pd) were used as model catalysts, both as a sputtered thin film and as nanoparticles supported on Îł-alumina. The thin films were characterized and tested in terms of their catalytic activity based on CO chemisorption measurements, stability and reproducibilit
Automated measurement method for assessing thermal-dependent electronic characteristics of thin boron-doped diamond-graphene nanowall structures
This paper investigates the electrical properties of boron-doped diamond-graphene (B:DG) nanostructures, focusing on their semiconductor characteristics. These nanostructures are synthesized on fused silica glass and Si wafer substrates to compare their behaviour on different surfaces. A specialized measurement system, incorporating Python-automated code, was developed for an in-depth analysis of electronic properties under various contact configurations. This approach allowed for a detailed exploration of charge transport mechanisms within the nanostructures. The research highlights a decrease in resistivity with increased deposition time, as shown by Arrhenius plot analysis. This trend is linked to the formation and evolution of multi-wall graphene structures. SEM images showed nanowall structures formed more readily on amorphous fused silica substrates, enabling unrestricted growth. TOF-SIMS analysis revealed uneven boron atom distribution through the film depth. A significant finding is a reduction in conductive activation energy in samples grown in microwave plasma from 197 meV to 87 meV as deposition time increased from 5 to 25 min. Furthermore, the study identifies a shift in transport mechanisms from variable range hopping (VRH) below 170 K to thermally activated (TA) conduction above 200 K. These insights advance our understanding of the electronic behaviours in B:DG nanostructures and underscore their potential in electronic device engineering, opening new paths for future research and technological developments.publishedVersio
EC-SERS detection of thiabendazole in apple juice using activated screen-printed electrodes
Thiabendazole (TBZ), a benzimidazole fungicide used for post-harvest treatment, may be a trace contaminant of food matrices. In this work, we report the first EC-SERS (electrochemical-surface enhanced Raman spectroscopy) detection of TBZ in spiked apple juice using electrochemically (EC) roughened, gold-based screen-printed electrodes (AuSPEs) and portable instrumentation. Polarizing the substrate (â0.8 V vs Ag/AgCl) improves the recorded SERS signal of TBZ, allowing to reach a limit of detection (LOD) in juice of 0.061 ppm with a relatively wide linear range (0.5â10 ÎźM) and good intermediate precision (%RSD < 10). The recovery of TBZ from unprocessed juice was found to be more than 82 %. Furthermore, a proof-of-concept integration of AuSPEs with a miniaturized flow cell for the preconcentration of TBZ and the controlled delivery of sample and reagents has been demonstrated. This approach paves the way for integrated, portable analytical systems applicable for on-site sample collection, processing, and analysis.publishedVersio
Toward microfluidic SERS and EC-SERS applications via tunable gold films over nanospheres
Many promising applications of surface-enhanced Raman scattering (SERS), such as microfluidic SERS and electrochemical (EC)-SERS, require immersion of plasmonic nanostructured films in aqueous media. Correlational investigations of the optical response and SERS efficiency of solid SERS substrates immersed in water are absent in the literature. This work presents an approach for tuning the efficiency of gold films over nanospheres (AuFoN) as SERS substrates for applications in aqueous environment. AuFoN are fabricated by convective self-assembly of colloidal polystyrene nanospheres of various diameters (300â800 nm), followed by magnetron sputtering of gold films. The optical reflectance of the AuFoN and Finite-Difference Time-Domain simulations in both water and air reveal the dependence of the surface plasmon band on nanospheresâ diameter and environment. SERS enhancement of a common Raman reporter on AuFoN immersed in water is analyzed under 785 nm laser excitation, but also using the 633 nm line for the films in air. The provided correlations between the SERS efficiency and optical response in both air and water indicate the best structural parameters for high SERS efficiency and highlight a route for predicting and optimizing the SERS response of AuFoN in water based on the behavior in air, which is more practical. Finally, the AuFoN are successfully tested as electrodes for EC-SERS detection of the thiabendazole pesticide and as SERS substrates integrated in a flow-through microchannel format. The obtained results represent an important step toward the development of microfluidic EC-SERS devices for sensing applications.publishedVersio
Microfluidic devices for photo-and spectroelectrochemical applications
The review presents recent developments in electrochemical devices for photo- and spectroelectrochemical investigations, with the emphasis on miniaturization (i.e., nanointerdigitated complementary metal-oxide-semiconductor devices, micro- and nano-porous silicon membranes or microoptoelectromechanical systems), silica glass/microreactors (i.e., plasmonic, Raman spectroscopy or optical microcavities) or polymer-based devices (i.e., 3D-printed, laser-engraved channels). Furthermore, we have evaluated inter alia the efficiency of various fabrication approaches for bioelectrochemical systems, biocatalysis, photochemical synthesis, or single nanoparticle spectroelectrochemistry. We envisioned the miniaturization of applied techniques such as cathodoluminescence, surface plasmon resonance, surface-enhanced Raman spectroscopy, voltametric and amperometric methods in the spectroelectrochemical microdevices. The research challenges and development perspectives of microfluidic, and spectroelectrochemical devices were also elaborated on.publishedVersio