Modellierung und Simulation des Verhaltens von durchströmten schaltbaren Membranen

Die schaltbare Filtration mithilfe von Hydrogel'=Verbundmembranen zeigt großes Potential zur Lösung einer der grundlegenden Aufgaben in der Humanmedizin: der unkomplizierten und schnellen Analyse von Blutproben zur Erkennung von Unregelmäßigkeiten, wie zum Beispiel zirkulierenden Tumorzellen. In der vorliegenden Arbeit wird ein solches System diskutiert und mithilfe von Methoden des Maschinenwesens -- Modellierung und Simulation -- untersucht. Das betrachtete System besteht aus einer aktiven Hydrogelschicht, welche auf einer passiven Polymerschicht aufgebracht ist und damit eine schaltbare Verbundmembran bildet. Die Arbeit folgt zwei Hauptpfaden: Im festkörpermechanischen Teil werden die mechanischen Aspekte von Verbundmembranen dargestellt, während im fluidmechanischen Teil die Permittivität und Selektivität von Membranen näher beleuchtet werden. Im Folgenden werden Modelle zur Schaltbarkeit ausgehend von aus der Literatur bekannten Ansätzen entwickelt. Diese werden dann im Rahmen von Simulationen -- sowohl im kommerziellen Finite-Elemente-Programm Abaqus, als auch in selbst geschriebenen Matlab-Codes -- umgesetzt. Die vorliegende Arbeit zeigt, dass ein schaltbares System zur Analyse von Zellgrößenprofilen realisierbar und durch Modellierung und Simulation in einem Maß beschreibbar ist, sodass der experimentellen Realisierung nichts mehr im Wege steht.Switchable filtration with hydrogel composite membranes shows great potential to solve one of the basic challenges in life sciences: the fast and easy analysis of blood samples to detect abnormal cells like e.g. circulating tumor cells. In the present work, a system providing these features is discussed using tools provided by engineering: modeling and simulation. The system consists of an active hydrogel composite membrane in combination with a passive polymeric membrane that provides mechanical stability. This forms a switchable composite membrane. The work follows two main paths: In the solid mechanics path, the composition of membranes and their mechanical aspects are discussed. The fluid mechanics path focuses on permittivity and selectivity for particle flows. Originating from the basic concepts of membrane permeation in literature, models for switchability are developed and simulations -- both in the commercial finite-element tool Abaqus and in Matlab scripts -- are performed. The present work proves that the concept of cell-size detection with switchable membranes is suitable for the task. Through the performed simulations, the corresponding processes can be described and designed so that the microfluidic analysis system can be experimentally realized

Window-opener as an example for environment measurement and combined actuation of smart hydrogels

An environment is defined by a set of field values, such as temperature, electro-magnetic field, light intensity, air humidity and air composition. Smart materials, such as hydrogels, are able to react to these kinds of stimuli. The spatial and time development of environmental values is governed by transport equations. Hence the reaction, i.e. actuation or sensing, of the smart material can be described based on the same assumptions. The displacement, here swelling and deswelling, of the material depends on the combination of the environmental parameters. Smart materials are called multi-sensitive, when more than one parameter is purposely used (i) to manipulate the material, i.e. as an actuator or (ii) to measure the quantities, i.e. as a (multi-)sensor. However, the material can also perform (iii) the objective of a logic processing unit in addition to (i) and (ii). In the current work, we present a device that realizes this concept: An automatic window opener that senses environmental parameters (light-level and air temperature) and reacts accordingly. The hydrogel material that is included in the simplistic device simultaneously acts as sensor, logic processing unit and actuator

Modeling and simulation of diffusion and reaction processes during the staining of tissue sections on slides

Histological slides are an important tool in the diagnosis of tumors as well as of other diseases that affect cell shapes and distributions. Until now, the research concerning an optimal staining time has been mainly done empirically. In experimental investigations, it is often not possible to stain an already-stained slide with another stain to receive further information. To overcome these challenges, in the present paper a continuum-based model was developed for conducting a virtual (re-)staining of a scanned histological slide. This model is capable of simulating the staining of cell nuclei with the dye hematoxylin (C.I. 75,290). The transport and binding of the dye are modeled (i) along with the resulting RGB intensities (ii). For (i), a coupled diffusion–reaction equation is used and for (ii) Beer–Lambert’s law. For the spatial discretization an approach based on the finite element method (FEM) is used and for the time discretization a finite difference method (FDM). For the validation of the proposed model, frozen sections from human liver biopsies stained with hemalum were used. The staining times were varied so that the development of the staining intensity could be observed over time. The results show that the model is capable of predicting the staining process. The model can therefore be used to perform a virtual (re-)staining of a histological sample. This allows a change of the staining parameters without the need of acquiring an additional sample. The virtual standardization of the staining is the first step towards universal cross-site comparability of histological slides

Permeation control in hydrogel-layered patterned PET membranes with defined switchable pore geometry – Experiments and numerical simulation

AbstractPermeation through polymeric membranes can be controlled by surface coating of a polyethylene terephthalate (PET) membrane with poly(N-isopropylacrylamide) (PNIPAAm) and inserting pores of defined geometry. When the temperature of the system rises above the volume phase transition temperature, the pores open, which allows permeation of formerly blocked particles. The exact control of the temperature allows defined change of the pore size and therefore enables separation abilities. Free swelling experiments are conducted to obtain the swelling behaviour of PNIPAAm. Then, a temperature expansion model is derived in order to simulate this behaviour with the finite element tool ABAQUS. The gained results are in excellent agreement with the observed shape change. Membranes with permeation control of particles can be used for biomedical application in microfluidics to analyse the size distribution of cells or in chemical information processing as a transistor-like component for an information-bearing chemical species. The possibility to simulate the behaviour of such permeation systems allows computer aided design and prediction of permeation abilities in these areas

Localized actuation of temperature responsive hydrogel-layers with a PCB-based micro-heater array

Space-resolved stimulation of active hydrogel layers can be achieved for example by using a micro-heater array. In the current work, we present the interaction of (i) such a rigid array of heating elements that can be selectively activated and (ii) an active thermo-responsive hydrogel layer that responds to the local stimulus change. Due to the respective local actuation, (iii) the surface form of a passive top-layer can be manipulated. We present continuum-based simulative predictions based on the Temperature Expansion Model and compare them to experimental outcomes for the system

Eleven strategies for making reproducible research and open science training the norm at research institutions

Across disciplines, researchers increasingly recognize that open science and reproducible research practices may accelerate scientific progress by allowing others to reuse research outputs and by promoting rigorous research that is more likely to yield trustworthy results. While initiatives, training programs, and funder policies encourage researchers to adopt reproducible research and open science practices, these practices are uncommon inmanyfields. Researchers need training to integrate these practicesinto their daily work. We organized a virtual brainstorming event, in collaboration with the German Reproducibility Network, to discuss strategies for making reproducible research and open science training the norm at research institutions. Here, weoutline eleven strategies, concentrated in three areas:(1)offering training, (2)adapting research assessment criteria and program requirements, and (3) building communities. We provide a brief overview of each strategy, offer tips for implementation,and provide links to resources. Our goal is toencourage members of the research community to think creatively about the many ways they can contribute and collaborate to build communities,and make reproducible research and open sciencetraining the norm. Researchers may act in their roles as scientists, supervisors, mentors, instructors, and members of curriculum, hiring or evaluation committees. Institutionalleadership and research administration andsupport staff can accelerate progress by implementing change across their institution

Eleven strategies for making reproducible research and open science training the norm at research institutions

Across disciplines, researchers increasingly recognize that open science and reproducible research practices may accelerate scientific progress by allowing others to reuse research outputs and by promoting rigorous research that is more likely to yield trustworthy results. While initiatives, training programs, and funder policies encourage researchers to adopt reproducible research and open science practices, these practices are uncommon inmanyfields. Researchers need training to integrate these practicesinto their daily work. We organized a virtual brainstorming event, in collaboration with the German Reproducibility Network, to discuss strategies for making reproducible research and open science training the norm at research institutions. Here, weoutline eleven strategies, concentrated in three areas:(1)offering training, (2)adapting research assessment criteria and program requirements, and (3) building communities. We provide a brief overview of each strategy, offer tips for implementation,and provide links to resources. Our goal is toencourage members of the research community to think creatively about the many ways they can contribute and collaborate to build communities,and make reproducible research and open sciencetraining the norm. Researchers may act in their roles as scientists, supervisors, mentors, instructors, and members of curriculum, hiring or evaluation committees. Institutionalleadership and research administration andsupport staff can accelerate progress by implementing change across their institution

Modellierung und Simulation des Verhaltens von durchströmten schaltbaren Membranen

Die schaltbare Filtration mithilfe von Hydrogel'=Verbundmembranen zeigt großes Potential zur Lösung einer der grundlegenden Aufgaben in der Humanmedizin: der unkomplizierten und schnellen Analyse von Blutproben zur Erkennung von Unregelmäßigkeiten, wie zum Beispiel zirkulierenden Tumorzellen. In der vorliegenden Arbeit wird ein solches System diskutiert und mithilfe von Methoden des Maschinenwesens -- Modellierung und Simulation -- untersucht. Das betrachtete System besteht aus einer aktiven Hydrogelschicht, welche auf einer passiven Polymerschicht aufgebracht ist und damit eine schaltbare Verbundmembran bildet. Die Arbeit folgt zwei Hauptpfaden: Im festkörpermechanischen Teil werden die mechanischen Aspekte von Verbundmembranen dargestellt, während im fluidmechanischen Teil die Permittivität und Selektivität von Membranen näher beleuchtet werden. Im Folgenden werden Modelle zur Schaltbarkeit ausgehend von aus der Literatur bekannten Ansätzen entwickelt. Diese werden dann im Rahmen von Simulationen -- sowohl im kommerziellen Finite-Elemente-Programm Abaqus, als auch in selbst geschriebenen Matlab-Codes -- umgesetzt. Die vorliegende Arbeit zeigt, dass ein schaltbares System zur Analyse von Zellgrößenprofilen realisierbar und durch Modellierung und Simulation in einem Maß beschreibbar ist, sodass der experimentellen Realisierung nichts mehr im Wege steht.Switchable filtration with hydrogel composite membranes shows great potential to solve one of the basic challenges in life sciences: the fast and easy analysis of blood samples to detect abnormal cells like e.g. circulating tumor cells. In the present work, a system providing these features is discussed using tools provided by engineering: modeling and simulation. The system consists of an active hydrogel composite membrane in combination with a passive polymeric membrane that provides mechanical stability. This forms a switchable composite membrane. The work follows two main paths: In the solid mechanics path, the composition of membranes and their mechanical aspects are discussed. The fluid mechanics path focuses on permittivity and selectivity for particle flows. Originating from the basic concepts of membrane permeation in literature, models for switchability are developed and simulations -- both in the commercial finite-element tool Abaqus and in Matlab scripts -- are performed. The present work proves that the concept of cell-size detection with switchable membranes is suitable for the task. Through the performed simulations, the corresponding processes can be described and designed so that the microfluidic analysis system can be experimentally realized

Stiffness pairing in soft-hard active-passive actuators

Soft-Hard Active-Passive Embedded Structures (SHAPES) are composites that respond to the environments in which they are embedded. This reaction can be a mechanical actuation, but also an intrinsic computation that yields an adaptation as a result. The actuation capabilities primarily depend on the stiffness combination of the involved materials. Stiffness includes both material parameters (depending on the chosen material model, e.g., the Young's modulus) and geometry parameters (depending on the type of structure, e.g., the beam height). The active properties can be included using the Stimulus Expansion Model, which is based on the analogy of the active reponse to thermal expansion. SHAPES can be designed according to three different behaviors, Case I constrained, Case II combined and Case III free. In the current work, these cases, the modelling and design background, and various examples are presented