Particle sorting by a structured microfluidic ratchet device with tunable selectivity: Theory and Experiment

We theoretically predict and experimentally demonstrate that several different particle species can be separated from each other by means of a ratchet device, consisting of periodically arranged triangular (ratchet) shaped obstacles. We propose an explicit algorithm for suitably tailoring the externally applied, time-dependent voltage protocol so that one or several, arbitrarily selected particle species are forced to migrate oppositely to all the remaining species. As an example we present numerical simulations for a mixture of five species, labelled according to their increasing size, so that species 2 and 4 simultaneously move in one direction and species 1, 3, and 5 in the other. The selection of species to be separated from the others can be changed at any time by simply adapting the voltage protocol. This general theoretical concept to utilize one device for many different sorting tasks is experimentally confirmed for a mixture of three colloidal particle species

Chiral particle separation by a non-chiral micro-lattice

We conceived a model experiment for a continuous separation strategy of chiral molecules (enantiomers) without the need of any chiral selector structure or derivatization agents: Micro-particles that only differ by their chirality are shown to migrate along different directions when driven by a steady fluid flow through a square lattice of cylindrical posts. In accordance with our numerical predictions, the transport directions of the enantiomers depend very sensitively on the orientation of the lattice relatively to the fluid flow

An Oil-Based Lubrication System Based on Nanoparticular TiO2 with Superior Friction and Wear Properties

Bogunovic L, Zünkeler S, Tönsing K, Anselmetti D. An Oil-Based Lubrication System Based on Nanoparticular TiO2 with Superior Friction and Wear Properties. Tribology Letters. 2015;29(2): 59.We evaluated the performance of five different commercially available nanoparticle classes as additives for an oil-based lubrication system. While the silicon dioxide particles Aerosil® 300, RY300, and R972V tended to increase wear and friction in our 100Cr6 versus cast iron disc–disc contact, Aeroxide® P 25 and especially T 805 TiO2 nanoparticles showed superior anti-wear and anti-friction properties. The underlying tribological mechanism was investigated with optical microscopy, helium ion microscopy, and X-ray photoelectron spectroscopy. Subsequently, we formulated a stable lubrication system based on the best performing T 805 particles. Here, the base oil is a highly purified paraffin oil which was supplemented with 1 wt% T 805 TiO2 particles, 1 wt% Estisol® 242 or 1 wt% oleic acid, 0.15 wt% oleylamine, and 0.15 wt% Pluronic® RPE 2520. Superior lubrication and anti-wear properties of this formulation were demonstrated in 4-h test runs with a normal force of F N = 2.5 kN and a sliding velocity of 0.15 m/s in our disc–disc contact. Wear was significantly reduced along with a nearly 12-fold reduction in the friction coefficient, compared to the base oil (μftobase=0.155vs.μftoT805≈0.01). Using 100Cr6 disc–ball contacts, we additionally analyzed the properties of our lubrication system in the border friction regime under higher loads (F N = 0.5 kN) in 2-h runs. In particular, on the discs with lower engagement ratio, chemo-tribological protective layers were built, which protected the parts very well against wear

Site-specific seeding using multi-sensor and data fusion techniques : a review

Site-specific seeding (SSS) is a precision agricultural (PA) practice aiming at optimizing seeding rate and depth, depending on the within field variability in soil fertility and yield potential. Unlike other site-specific applications, SSS was not adopted sufficiently by farmers due to some technological and practical challenges that need to be overcome. Success of site-specific application strongly depends on the accuracy of measurement of key parameters in the system, modeling and delineation of management zone maps, accurate recommendations and finally the right choice of variable rate (VR) technologies and their integrations. The current study reviews available principles and technologies for both map-based and senor-based SSS. It covers the background of crop and soil quality indicators (SQI), various soil and crop sensor technologies and recommendation approaches of map-based and sensor-based SSS applications. It also discusses the potential of socio-economic benefits of SSS against uniform seeding. The current review proposes prospective future technology synthesis for implementation of SSS in practice. A multi-sensor data fusion system, integrating proper sensor combinations, is suggested as an essential approach for putting SSS into practice

Migration and separation in structured microfluidic systems

Bogunovic L. Migration and separation in structured microfluidic systems. Bielefeld: Bielefeld University; 2013.Spatially structured microfluidic channels in a state far from thermal equilibrium have been developed to address three fundamental problems in modern (bio-)analytics: the usually fixed separation criterion (e.g. a gel density is not changeable on the fly), the usually unknown polarizability properties of samples for dielectrophoretic manipulation and the requirement of a specifically designed chiral selector for chiral separation. 1) Typical biotechnological separation techniques like filters, chromatography, or gel electrophoresis have a fixed implemented separation criterion, e.g. defined by pore size, affinity of the steady phase, or gel density. To overcome this limit, the aim of the first project is the development and functional characterization of a microfluidic ratchet device with a dynamically changeable separation criterion. Depending on the applied voltage scheme, an arbitrarily selectable sub-group of the available species in the analyte solution is forced to migrate into opposite direction than the remaining species. Changing the voltage scheme will immediately switch the separation criterion. The device is based on a sophisticated interplay between electrophoresis and dielectrophoresis and operates with any charged and polarizable material in solution such as e.g. micro- and nanoparticles, cells, or biomolecules. 2) Many microfluidic systems rely on dielectrophoresis to immobilize, manipulate, or sort a somehow polarizable sample. However, the actual polarizability value usually remains unknown and appropriate electric fields to trigger dielectrophoresis are found via trial and error. The second project uses dielectrophoretic traps in a tilted potential implemented in a microfluidic channel to automatically quantify single molecule (here DNA) polarizabilities via fluorescence video microscopy. The approach is tested by reproducing a well-known scaling law between the buffer solution’s ionic strength and the polarizability for two different DNA types. In a second experiment the influence of the required fluorescence staining on the polarizability is investigated. Besides the pure quantification of polarizability in basic research, this system could be used to automatically tune dielectrophoretic traps in a final product to broaden its range of possible analyte classes. 3)When chiral molecules are about to be separated after synthesis, a chromatography setup is used which typically requires chiral selection or derivatization agents. Usually these chemicals have to be redeveloped for every new analyte. The third project’s aim is the implementation of a generic and continuously operating principle to separate chiral molecules in microfluidic channels without the need for any chiral selection or derivatization agent. Two conceptually different microfluidic approaches with excellent sorting performance were developed and experimentally evaluated. Following Curie’s principle, both approaches rely on microfluidic structures that somehow break the symmetry in the channel in every relevant dimension. Injected model enantiomers are demonstrated to split up according to their chirality and to accumulate near opposite channel walls

Fabrication of a microfluidic channel with differently modified surfaces with a two component approach

Bogunovic L, Vosskötter C, Anselmetti D. Fabrication of a microfluidic channel with differently modified surfaces with a two component approach. Journal of Micromechanics and Microengineering. 2014;24(7): 77001.We report on a two-component fabrication technique for microfluidic channels, allowing for different chemical or physical surface modifications of channel walls within one single channel. The two components are made of polydimethylsiloxane and prepared via soft lithography independently. After appropriate pre-treatment with the desired functions, the two parts are bonded together using oxygen plasma and a Fineplacer® lambda system. As a proof of concept, we present the combination of electroosmosis and opposing hydrodynamic flow in a microfluidic channel leading to different velocity presigns of the resulting flow on opposite channel walls, due to different surface modifications. These results indicate an intact Pluronic® F108 surface coating after assembly

Echocardiographically derived effective valve opening area in mitral prostheses: a comparative analysis of various calculations using continuity equation and pressure half time method

Bogunovic N, Horstkotte D, Faber L, Bogunovic L, van Buuren F. Echocardiographically derived effective valve opening area in mitral prostheses: a comparative analysis of various calculations using continuity equation and pressure half time method. Heart and Vessels. 2016;31(6):932-938.Detection of dysfunctional mitral valve prostheses (MP) remains complex even though being optimized by considering echocardiographically derived prosthetic effective orifice area (VA). The purpose was to compare VA in MP, calculated by the continuity equation (CE) using peak velocities (CEVpeak), mean velocities (CEVmean), velocity–time integrals (CEVTI) and the pressure half time method using 220 ms as constant first (PHT220) as well as optimized constants. In 267 consecutive patients with normally functioning MP, we investigated VA within the first postoperative month. With increasing prosthetic sizes, mean VA values also increase in all calculations. The statistical curves demonstrate no significant difference in graphical steepness but show different levels. Comparison of mean VA showed the known systematic higher values of PHT220 and significantly decreased results when using CEVTI. This systematic difference between mean VA applying PHT220 versus CEVTI is approximately 1.0 cm2 for all prosthetic sizes. Calculations via CEVpeak were close to the results of CEVTI. CEVmean produced values, which graphically correspond to the PHT220 curve. Only PHT220 detected the constructional equal prosthetic inner ring width between 29 and 31 mm. To compensate the systematic difference between CEVTI and PHT220, an optimized constant of 140 ms was calculated to be applied in PHT (PHT140). VA is a robust and, therefore, preferable parameter for investigating MP. If needed, both CE and PHT are applicable with a systematical difference between CEVTI and PHT220. An optimized constant of 140 ms (PHT140) should be applied when calculating VA of mitral valve prostheses via PHT

Radiation protection during cardiac catherization: development of an improved lead apron for periinterventional echocardiography

Bogunovic N, Horstkotte D, Faber L, Bogunovic L, Van Buuren F. Radiation protection during cardiac catherization: development of an improved lead apron for periinterventional echocardiography. Minerva Cardioangiologica. 2015;63(5):458-460

Physiological left ventricular segmental myocardial mechanics: Multi-parametric polar mapping to determine intraventricular gradients of myocardial dynamics

Bogunovic N, van Buuren F, Esdorn H, Horstkotte D, Bogunovic L, Faber L. Physiological left ventricular segmental myocardial mechanics: Multi-parametric polar mapping to determine intraventricular gradients of myocardial dynamics. ECHOCARDIOGRAPHY-A JOURNAL OF CARDIOVASCULAR ULTRASOUND AND ALLIED TECHNIQUES. 2018;35(12):1947-1955.Objective: We investigated physiological systolic left ventricular (LV) myocardial mechanics and gradients to provide a database for later studies of diseased hearts. Methods: The analyses were performed in 131 heart-healthy individuals and included seven parameters of myocardial mechanics using speckle tracking echocardiography (STE). Results: Basal to apical and circumferentially significant physiological intraventricular parameter gradients of myocardial activity were determined. Global mean values and segmental ranges were peak systolic longitudinal strain -21.2 +/- 3.3%, 95% confidence interval [CI] -21.8% to -20.6%), gradient (basal to apical) -16.0% to -26.7%; peak systolic longitudinal strain rate -1.24 +/- 0.31%/s, 95% CI -1.29% to -1.19%/s, gradient (basal to apical) -0.91% to -1.61%/s; post-systolic index 2.6 +/- 3.2%, 95% CI 3.15%-2.05%, gradient (basal/medial/apical) 7.0/1.2/2.4%; pre-systolic stretch index 1.3 +/- 2.7%, 95% CI 1.77%-0.83%, gradient (basal/medial/apical) 6.5/0.2/1.3%; peak longitudinal displacement 12.2 +/- 2.6 mm, 95% CI 12.6-11.8 mm, gradient (basal to apical) 21.0-3.4 mm; time-to-peak longitudinal strain 370 +/- 43 ms, 95% CI 377-363 ms, gradient (basal to apical) 396-361 ms; and time-to-peak longitudinal strain rate 180 +/- 47 ms, 95% CI 188-172 ms, gradient (basal to apical) 150-200 ms. Conclusion: This study generated a database of seven STE-derived parameters of physiological segmental and global myocardial LV mechanics. The resulting sets of three-dimensional intraventricular mappings of the entire LV provide physiological parameter gradients in baso-apical and circumferential direction by applying the 17-segment polar model. This will facilitate comparison of systolic myocardial activity of the healthy LV with diseased or otherwise altered (eg, sports) hearts

A differentiated morphological parameter-coding system to describe the suitability of mitral valve stenoses intended for percutaneous valvotomy

Bogunovic N, Horstkotte D, Scholtz W, Faber L, Bogunovic L, van Buuren F. A differentiated morphological parameter-coding system to describe the suitability of mitral valve stenoses intended for percutaneous valvotomy. Heart and Vessels. 2014;30(5):632-641