Spatial activity profiling along a fixed bed of powder catalyst during selective oxidation of propylene to acrolein

Spatial profiling of the reactant and product concentration including the gas phase temperature during the selective oxidation of propylene to acrolein along a catalyst bed allowed locating and distinguishing between specific processes occurring in each individual point of a chemical reactor. For this purpose, a lab-scale testing setup capable of resolving concentration and temperature gradients in a fixed-bed reactor was developed. The local gas phase composition and temperature were determined using a sampling capillary and mass spectrometry along a multicomponent Bi–Mo–Co–Fe oxide catalyst bed during selective oxidation of propylene to acrolein under high conversion conditions. In this way, the reaction progress in terms of conversion, selectivities and yields along the reactor was revealed. While ca. 66% of the integral propylene conversion occurred in the first third of the catalyst bed with high selectivity towards acrolein, the latter third of the bed was dominated by the formation of acrylic acid and CO$_{2}$ as further and total oxidation products, respectively. Acrylic acid, which originates from the sequential oxidation of propylene to acrolein, was the by-product with the highest yield and especially formed above 440 °C. CO and CO$_{2}$ were observed directly from propylene, along with consecutive pathways of propylene oxidation, which favor CO$_{2}$ formation. The numerous insights obtained by even a single profile highlight the strong capabilities of spatially resolved activity and temperature measurements for diagnostics of packed-bed reactors and identifying the reaction pathways occurring within

Laser-Treated Surfaces for VADs: From Inert Titanium to Potential Biofunctional Materials

Laser-treated surfaces for ventricular assist devices. Impact Statement. This work has scientific impact since it proposes a biofunctional surface created with laser processing in bioinert titanium. Introduction. Cardiovascular diseases are the world’s leading cause of death. An especially debilitating heart disease is congestive heart failure. Among the possible therapies, heart transplantation and mechanical circulatory assistance are the main treatments for its severe form at a more advanced stage. The development of biomaterials for ventricular assist devices is still being carried out. Although polished titanium is currently employed in several devices, its performance could be improved by enhancing the bioactivity of its surface. Methods. Aiming to improve the titanium without using coatings that can be detached, this work presents the formation of laser-induced periodic surface structures with a topology suitable for cell adhesion and neointimal tissue formation. The surface was modified by femtosecond laser ablation and cell adhesion was evaluated in vitro by using fibroblast cells. Results. The results indicate the formation of the desired topology, since the cells showed the appropriate adhesion compared to the control group. Scanning electron microscopy showed several positive characteristics in the cells shape and their surface distribution. The in vitro results obtained with different topologies point that the proposed LIPSS would provide enhanced cell adhesion and proliferation. Conclusion. The laser processes studied can create new interactions in biomaterials already known and improve the performance of biomaterials for use in ventricular assist devices

Organic semiconductor distributed feedback laser pixels for lab-on-a-chip applications fabricated by laser-assisted replication

The integration of organic semiconductor distributed feedback (DFB) laser sources into all-polymer chips is promising for biomedical or chemical analysis. However{,} the fabrication of DFB corrugations is often expensive and time-consuming. Here{,} we apply the method of laser-assisted replication using a near-infrared diode laser beam to efficiently fabricate inexpensive poly(methyl methacrylate) (PMMA) chips with spatially localized organic DFB laser pixels. This time-saving fabrication process enables a pre-defined positioning of nanoscale corrugations on the chip and a simultaneous generation of nanoscale gratings for organic edge-emitting laser pixels next to microscale waveguide structures. A single chip of size 30 mm [times] 30 mm can be processed within 5 min. Laser-assisted replication allows for the subsequent addition of further nanostructures without a negative impact on the existing photonic components. The minimum replication area can be defined as being as small as the diode laser beam focus spot size. To complete the fabrication process{,} we encapsulate the chip in PMMA using laser transmission welding

Laser-Treated Surfaces for VADs: From Inert Titanium to Potential Biofunctional Materials

Objective. Laser-treated surfaces for ventricular assist devices. Impact Statement. This work has scientific impact since it proposes a biofunctional surface created with laser processing in bioinert titanium. Introduction. Cardiovascular diseases are the world’s leading cause of death. An especially debilitating heart disease is congestive heart failure. Among the possible therapies, heart transplantation and mechanical circulatory assistance are the main treatments for its severe form at a more advanced stage. The development of biomaterials for ventricular assist devices is still being carried out. Although polished titanium is currently employed in several devices, its performance could be improved by enhancing the bioactivity of its surface. Methods. Aiming to improve the titanium without using coatings that can be detached, this work presents the formation of laser-induced periodic surface structures with a topology suitable for cell adhesion and neointimal tissue formation. The surface was modified by femtosecond laser ablation and cell adhesion was evaluated in vitro by using fibroblast cells. Results. The results indicate the formation of the desired topology, since the cells showed the appropriate adhesion compared to the control group. Scanning electron microscopy showed several positive characteristics in the cells shape and their surface distribution. The in vitro results obtained with different topologies point that the proposed LIPSS would provide enhanced cell adhesion and proliferation. Conclusion. The laser processes studied can create new interactions in biomaterials already known and improve the performance of biomaterials for use in ventricular assist devices

Gazette de Bayonne, de Biarritz et du Pays basque

18 mars 19381938/03/18 (A47,N9100).Appartient à l’ensemble documentaire : Aquit

Tailored Surface-Enhanced Raman Nanopillar Arrays Fabricated by Laser-Assisted Replication for Biomolecular Detection Using Organic Semiconductor Lasers

Organic semiconductor distributed feedback (DFB) lasers are of interest as external or chip-integrated excitation sources in the visible spectral range for miniaturized Raman-on-chip biomolecular detection systems. However, the inherently limited excitation power of such lasers as well as oftentimes low analyte concentrations requires efficient Raman detection schemes. We present an approach using surface-enhanced Raman scattering (SERS) substrates, which has the potential to significantly improve the sensitivity of on-chip Raman detection systems. Instead of lithographically fabricated Au/Ag-coated periodic nanostructures on Si/SiO₂ wafers, which can provide large SERS enhancements but are expensive and time-consuming to fabricate, we use low-cost and large-area SERS substrates made <i>via</i> laser-assisted nanoreplication. These substrates comprise gold-coated cyclic olefin copolymer (COC) nanopillar arrays, which show an estimated SERS enhancement factor of up to ∼10⁷. The effect of the nanopillar diameter (60–260 nm) and interpillar spacing (10–190 nm) on the local electromagnetic field enhancement is studied by finite-difference-time-domain (FDTD) modeling. The favorable SERS detection capability of this setup is verified by using rhodamine 6G and adenosine as analytes and an organic semiconductor DFB laser with an emission wavelength of 631.4 nm as the external fiber-coupled excitation source

Organic semiconductor distributed feedback laser pixels for lab-on-a-chip applications fabricated by laser-assisted replication

The integration of organic semiconductor distributed feedback (DFB) laser sources into all-polymer chips is promising for biomedical or chemical analysis. However{,} the fabrication of DFB corrugations is often expensive and time-consuming. Here{,} we apply the method of laser-assisted replication using a near-infrared diode laser beam to efficiently fabricate inexpensive poly(methyl methacrylate) (PMMA) chips with spatially localized organic DFB laser pixels. This time-saving fabrication process enables a pre-defined positioning of nanoscale corrugations on the chip and a simultaneous generation of nanoscale gratings for organic edge-emitting laser pixels next to microscale waveguide structures. A single chip of size 30 mm [times] 30 mm can be processed within 5 min. Laser-assisted replication allows for the subsequent addition of further nanostructures without a negative impact on the existing photonic components. The minimum replication area can be defined as being as small as the diode laser beam focus spot size. To complete the fabrication process{,} we encapsulate the chip in PMMA using laser transmission welding