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2021 ◽  
Author(s):  
Zuyao Xiao ◽  
Audrey Nsamela ◽  
Benjamin Garlan ◽  
Juliane Simmchen

The ability of artificial microswimmers to respond to external stimuli and the mechanistical details of their origins belong to the most disputed challenges in interdisciplinary science. Therein, the creation of chemical gradients is technically challenging, because they quickly level out due to diffusion. Inspired by pivotal stopped flow experiments in chemical kinetics, we show that microfluidics gradient generation combined with a pressure feedback loop for precisely controlling the stop of the flows, can enable us to study mechanistical details of chemotaxis of artificial Janus micromotors, based on a catalytic reaction. We find that these copper Janus particles display a chemotactic motion along the concentration gradient in both, positive and negative direction and we demonstrate the mechanical reaction of the particles to small forces deviations, explaining this behaviour.


2021 ◽  
Vol 92 (12) ◽  
pp. 123001
Author(s):  
David Buhrke ◽  
Jeannette Ruf ◽  
Philipp Heckmeier ◽  
Peter Hamm

Author(s):  
Nico Symma ◽  
Andreas Hensel

AbstractProanthocyanidins (PAC) are an important and widely spread class of natural products with various bioactivities. The analytical evaluation of oligomeric and polymeric proanthocyanidins in complex extracts is still challenging, due to the complexity of structures. Nevertheless, in the last 20 years analytical techniques especially in the field of chromatography and mass spectrometry have been improved and offer exciting possibilities for a deeper insight into plant secondary metabolism. While classical colorimetric methods and protocols for partial hydrolysis are still valuable tools new chromatographically and mass spectrometric methods provide deep insights into the PAC fine structure, also of polymeric material. The present review focus on recent innovative LC–MS and MALDI-TOF methods, innovative strategies for advanced processing of LC-HRMS data (van Krevelen plots, Kendrick Mass Defect Analysis), MS/MS fragmentation, and newest two-dimensional LC × LC (Offline, Online, Stop-flow-2D) chromatography. Also MALDI-TOF imaging provides exciting inside in PAC distribution within biological samples and functional assays.


Catalysts ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 688
Author(s):  
Tyko Viertiö ◽  
Viivi Kivelä ◽  
Matti Putkonen ◽  
Johanna Kihlman ◽  
Pekka Simell

Steel filter discs were catalytically activated by ALD, using a coating of supporting Al2O3 layer and an active NiO layer for gas cleaning. Prepared discs were tested for model biomass gasification and gas catalytic filtration to reduce or eliminate the need for a separate reforming unit for gasification gas tars and lighter hydrocarbons. Two different coating methods were tested. The method utilizing the stop-flow setting was shown to be the most suitable for the preparation of active and durable catalytic filters, which significantly decreases the amount of tar compounds in gasification gas. A pressure of 5 bar and temperatures of over 850 °C are required for efficient tar reforming. In optimal conditions, applying catalytic coating to the filter resulted in a seven-fold naphthalene conversion increase from 7% to 49%.


2021 ◽  
Author(s):  
Navid Hakimi

Polymer-based microparticles are increasingly utilized in a range of biotechnology application. There is growing evidence that microparticle shape is an important parameter governing its functionality. Yet, there currently exists no straightforward method to controllably synthesize a large number of highly three-dimensional (3D) microparticles. In this thesis, we develop a one-step two-dimensional (2D) stop-flow lithography method that exploits the non-uniformity of the polymerizing ultraviolet (UV) light, UV adsorption by opaque nanoparticles in the precursor solution, and discontinuous photomask patterns, to make highly curved 3D microparticles. We investigate the microparticle shape dependence on each parameter by independently tuning the field and focus of the UV light, adding opaque magnetic nanoparticles to the precursor solution, and using a variety of photomask patterns.We also perform numerical simulations of oxygen concentration and monomer conversion in the microfluidic channel, to predict the particle shape. By simplifying the synthesis of high curvature 3D particles with 3D surface features and branched structures, our method may lead to the expanded use of microparticles in research and in industry.


2021 ◽  
Author(s):  
Navid Hakimi

Polymer-based microparticles are increasingly utilized in a range of biotechnology application. There is growing evidence that microparticle shape is an important parameter governing its functionality. Yet, there currently exists no straightforward method to controllably synthesize a large number of highly three-dimensional (3D) microparticles. In this thesis, we develop a one-step two-dimensional (2D) stop-flow lithography method that exploits the non-uniformity of the polymerizing ultraviolet (UV) light, UV adsorption by opaque nanoparticles in the precursor solution, and discontinuous photomask patterns, to make highly curved 3D microparticles. We investigate the microparticle shape dependence on each parameter by independently tuning the field and focus of the UV light, adding opaque magnetic nanoparticles to the precursor solution, and using a variety of photomask patterns.We also perform numerical simulations of oxygen concentration and monomer conversion in the microfluidic channel, to predict the particle shape. By simplifying the synthesis of high curvature 3D particles with 3D surface features and branched structures, our method may lead to the expanded use of microparticles in research and in industry.


2021 ◽  
Author(s):  
Bridget L Evans ◽  
Adam F L Hurlstone ◽  
Peter E Clayton ◽  
Adam Stevens ◽  
Holly A Shiels

AbstractRespirometry is the current gold-standard for measuring metabolic rate. However, there is a growing need for metabolic rate measurements suitable for developmental studies, particularly in Danio rerio, where many important developmental stages occur at < 4 mm. While many metabolic studies rely on respirometry, the cost and complexity of the equipment limits its appeal in non-specialist labs, and background respiration becomes increasingly problematic as the size of the organism reduces. Here, glucose uptake was compared to stop-flow respirometry as an alternative measure of metabolic rate more suitable to the small scale required for developmental studies. A Passing-Bablok regression revealed the rate of glucose uptake can be considered equivalent to oxygen consumption as a measure of metabolic rate in Danio rerio larvae within a 95% limit of agreement. Therefore, glucose uptake is a valid alternative to the gold-standard in small organisms where conventional respirometry is problematic.Summary statementThe rate of glucose uptake is a valid alternative to respirometry for metabolic rate measurements in small larval fish.


Author(s):  
Alejandro M. Alcaraz ◽  
Johanna Eva Maria Schmidt ◽  
Paolo Colombo ◽  
Carlos Martinez

2020 ◽  
Vol 117 (36) ◽  
pp. 21865-21872
Author(s):  
Rumen N. Georgiev ◽  
Sara O. Toscano ◽  
William E. Uspal ◽  
Bram Bet ◽  
Sela Samin ◽  
...  

Comprehensive understanding of particle motion in microfluidic devices is essential to unlock additional technologies for shape-based separation and sorting of microparticles like microplastics, cells, and crystal polymorphs. Such particles interact hydrodynamically with confining surfaces, thus altering their trajectories. These hydrodynamic interactions are shape dependent and can be tuned to guide a particle along a specific path. We produce strongly confined particles with various shapes in a shallow microfluidic channel via stop flow lithography. Regardless of their exact shape, particles with a single mirror plane have identical modes of motion: in-plane rotation and cross-stream translation along a bell-shaped path. Each mode has a characteristic time, determined by particle geometry. Furthermore, each particle trajectory can be scaled by its respective characteristic times onto two master curves. We propose minimalistic relations linking these timescales to particle shape. Together these master curves yield a trajectory universal to particles with a single mirror plane.


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