3D-printed digital pneumatic logic for the control of soft robotic actuators.

Soft robots are paving their way to catch up with the application range of metal-based machines and to occupy fields that are challenging for traditional machines. Pneumatic actuators play an important role in this development, allowing the construction of bioinspired motion systems. Pneumatic logic gates provide a powerful alternative for controlling pressure-activated soft robots, which are often controlled by metallic valves and electric circuits. Many existing approaches for fully compliant pneumatic control logic suffer from high manual effort and low pressure tolerance. In our work, we invented three-dimensional (3D) printable, pneumatic logic gates that perform Boolean operations and imitate electric circuits. Within 7 hours, a filament printer is able to produce a module that serves as an OR, AND, or NOT gate; the logic function is defined by the assigned input signals. The gate contains two alternately acting pneumatic valves, whose work principle is based on the interaction of pressurized chambers and a 3D-printed 1-millimeter tube inside. The gate design does not require any kind of support material for its hollow parts, which makes the modules ready to use directly after printing. Depending on the chosen material, the modules can operate on a pressure supply between 80 and more than 750 kilopascals. The capabilities of the invented gates were verified by implementing an electronics-free drink dispenser based on a pneumatic ring oscillator and a 1-bit memory. Their high compliance is demonstrated by driving a car over a fully flexible, 3D-printed robotic walker controlled by an integrated circuit.

High-order simulation scheme for active particles driven by stress boundary conditions.

We study the dynamics and interactions of elliptic active particles in a two dimensional solvent. The particles are self-propelled through prescribing a fluid stress at one half of the fluid-particle boundary. The fluid is treated explicitly solving the Stokes equation through a discontinuous Galerkin scheme, which allows to simulate strictly incompressible fluids. We present numerical results for a single particle and give an outlook on how to treat suspensions of interacting active particles.

[Urological care in practices and clinics during the corona virus pandemic in Germany]. / Versorgungssituation urologischer Patienten in Praxen und Kliniken während der Coronaviruspandemie in Deutschland.

The coronavirus pandemic has had an immediate and far-reaching effect on the care of urological patients. The pandemic monitor of the German Society for Urology was able to record the restrictions on patient care in urological practices and clinics by means of regular surveys of the members. A total of 689 responses at four survey time points were included. In April there was a reduction in urological inpatients to 44% and the number of patients in practices dropped to 50%. Available operating theater capacities for urological patients were 45% in April, normalized to 90% in June and fell again to 50% in December. Elective operations could not be performed at all or only to a very limited extent in most hospitals in April and December. While urgent operations could be treated to 100% in more than 75% of the clinics in April, in December more than half of the clinics stated that they could not treat all patients with urgent indications. To some extent (8-19%) practices and clinics had to resort to a pandemic-related supraregional referral of patients. The reduction of outpatients in urological practices in April normalized to 95% in June and remained stable during the second wave of the pandemic. The increase in urological emergencies in practices observed at the beginning of the pandemic did not show up in November and December. The coronavirus pandemic has led to a significant reduction in the care of urological patients, which in particular in the second wave also affects urgent operations.

[Analysis of European concepts for specialization training in urology with special consideration of intersectoral further education]. / Analyse von europäischen Weiterbildungskonzepten zum Facharzt für Urologie unter besonderer Berücksichtigung der intersektoralen Weiterbildung.

BACKGROUND: The aim of the study is to compare the German specialization training in urology with other European concepts, to analyze regional differences and to evaluate the development of the personnel structure in urology in German hospitals and private practices for the last 5 years. In addition, possibilities for financial funding of residents in the outpatient sector will be analyzed. MATERIALS AND METHODS: After analyzing the changes in the new Urology Specialization Training Regulations (Musterweiterbildungsordnung), the current urology training situation in Germany was evaluated in a European comparison. A trend analysis of the personnel structure in urology has been performed for recent years. Additionally, a possible intersectoral rotation concept was developed. Financial funding possibilities for urological residents were evaluated in a standardized telephone survey. RESULTS: Compared to other European countries, the exceptional position of German urology with its enormous spectrum becomes evident. In some states, there are already possibilities of financial support provided by regional Associations of Statutory Health Insurance Physicians (Krankenversicherung) for the training of urological residents in private practices. CONCLUSIONS: While the organization of specialization training is commonly nation based in other European countries, there is heterogeneity in Germany due to the sovereignty of the states. Due to the shift of many specialization training contents towards the outpatient sector, alliances between clinics and practices in the sense of intersectoral training will become more important in the future. Therefore, the use of already existing funds and-as a long-term objective-a nationwide access to such funding is desirable.

[Urology in the corona-virus pandemic-a guideline 4/20]. / Urologie in der Corona-Virus-Pandemie ­ Leitfaden 4/20.

The coronavirus pandemic is a major challenge for healthcare systems worldwide. For urology, the expansion of the health-care structures for the treatment of patients suffering from COVID-19 should be supported as best as possible. At the same time, one should aim to ensure adequate care for urological emergencies and urgent urological treatments as far as possible, even during the pandemic. For this, patients must be prioritized individually, alternative therapy concepts must be considered and regional and supraregional cooperation must be used. Outpatient departments are of great importance in the care, examination and coordination of urological emergencies and urgent treatment. Urological clinics must prepare themselves to perform urgent operations and interventions on SARS-CoV­2-positive patients. Here, the creation of a separate, appropriately equipped emergency operating room to perform operations and interventions on SARS-CoV­2 patients should be considered. Furthermore strictly defined hygiene measures to protect employees in various clinical scenarios should be set up.

Comparative Prey Spectra Analyses on the Endangered Aquatic Carnivorous Waterwheel Plant (Aldrovanda vesiculosa, Droseraceae) at Several Naturalized Microsites in the Czech Republic and Germany.

The critically endangered carnivorous waterwheel plant (Aldrovanda vesiculosa, Droseraceae) possesses underwater snap traps for capturing small aquatic animals, but knowledge on the exact prey species is limited. Such information would be essential for continuing ecological research, drawing conclusions regarding trapping efficiency and trap evolution, and eventually, for conservation. Therefore, we performed comparative trap size measurements and snapshot prey analyses at seven Czech and one German naturalized microsites on plants originating from at least two different populations. One Czech site was sampled twice during 2017. We recorded seven main prey taxonomic groups, that is, Cladocera, Copepoda, Ostracoda, Ephemeroptera, Nematocera, Hydrachnidia, and Pulmonata. In total, we recorded 43 different prey taxa in 445 prey-filled traps, containing in sum 461 prey items. With one exception, prey spectra did not correlate with site conditions (e.g. water depth) or trap size. Our data indicate that A. vesiculosa shows no prey specificity but catches opportunistically, independent of prey species, prey mobility mode (swimming or substrate-bound), and speed of movement. Even in cases where the prey size exceeded trap size, successful capture was accomplished by clamping the animal between the traps' lobes. As we found a wide prey range that was attracted, it appears unlikely that the capture is enhanced by specialized chemical- or mimicry-based attraction mechanisms. However, for animals seeking shelter, a place to rest, or a substrate to graze on, A. vesiculosa may indirectly attract prey organisms in the vicinity, whereas other prey capture events (like that of comparably large notonectids) may also be purely coincidental.

Nonequilibrium depletion interactions in active microrheology.

Entropic depletion forces arise between mesoscopic bodies that are immersed in a suspension of macromolecules, such as colloid-polymer mixtures. Here we consider the case of a driven colloidal probe in the presence of another, passive colloidal particle, both solvated in an ideal bath of small spherical particles. We calculate the nonequilibrium forces mediated by the depletants on the two colloidal particles within a dynamical superposition approximation (DSA) scheme. In order to assess the quality of this approximation, and to obtain the colloidal microstructure around the driven probe, we corroborate our theoretical results with Brownian dynamics simulations.

Driven Brownian particle as a paradigm for a nonequilibrium heat bath: Effective temperature and cyclic work extraction.

We apply the concept of a frequency-dependent effective temperature based on the fluctuation-dissipation ratio to a driven Brownian particle in a nonequilibrium steady state. Using this system as a thermostat for a weakly coupled harmonic oscillator, the oscillator thermalizes according to a canonical distribution at the respective effective temperature across the entire frequency spectrum. By turning the oscillator from a passive thermometer into a heat engine, we realize the cyclic extraction of work from a single thermal reservoir, which is feasible only due to its nonequilibrium nature.

[Non-muscle-invasive bladder cancer: Information transfer from the clinic to the doctor's office : Results of a questionnaire study and presentation of a software solution]. / Nicht muskelinvasives Harnblasenkarzinom: Risikostratifizierung und Befundweitergabe : Ergebnisse einer Fragebogenstudie und Vorstellung einer Softwarelösung.

BACKGROUND AND OBJECTIVES: The adjuvant treatment of non-muscle-invasive bladder cancer (NMIBC) is based on the individual risk profile (RP) and its sufficient transfer from the clinic to the doctor's office. The objectives of our study were to verify the importance and degree of transfer of RP and recommendation for risk-adapted adjuvant treatment (RAAT) in patients with NMIBC as well as to develop appropriate tools for this purpose, if necessary. MATERIALS AND METHODS: An email-based survey distributed to urologists in Brandenburg, Berlin, Bavaria and Lower Saxony explored the questions mentioned above. In addition, a tool for risk stratification and information transfer for patients with NMIBC was developed and validated. RESULTS: From a total of 134 questionnaires analyzed, 55 were from clinic urologists (CUs) and 79 were from ambulant urologists (AUs). Although 9 out of 10 urologists considered the RP of importance, only 29 % of CUs and 24 % of AUs (p = 0.553) confirmed that the RP was always mentioned in medical reports. The recommendation for RAAT was confirmed from 62 % of CUs and 20 % of AUs (p < 0.001). A recommendation for RAAT in the medical report was requested by 86 % of AUs. The risk calculator presented here - to our knowledge the first with integration of the 2004 WHO grading - is delivered in all mathematically possible constellations a RP, according to guideline recommendations. CONCLUSION: Urologists in the clinic and doctor's office both attach considerable importance to the determination and transfer of RP and the recommendation for RAAT. There was evidence to suggest an overestimation of the quality of medical reports by the CU. The risk calculator provides an easy and cost-neutral option to improve risk stratification and information transfer from the clinic to the doctor's office.

Biomimetic optimisation of branched fibre-reinforced composites in engineering by detailed analyses of biological concept generators.

The aim of this study is the biomimetic optimisation of branched fibre-reinforced composites based on the detailed analysis of biological concept generators. The methods include analyses of the functional morphology and biomechanics of arborescent monocotyledons and columnar cacti as well as measurements and modelling of mechanical properties of biomimetic fibre-reinforced composites. The key results show evidence of notch stress reduction by optimised stem-branch-attachment morphology in monocotyledons and columnar cacti. It could be shown that some of these highly interesting properties can be transferred into biomimetic fibre-reinforced composites.

Biomimetic cellular metals-using hierarchical structuring for energy absorption.

Fruit walls as well as nut and seed shells typically perform a multitude of functions. One of the biologically most important functions consists in the direct or indirect protection of the seeds from mechanical damage or other negative environmental influences. This qualifies such biological structures as role models for the development of new materials and components that protect commodities and/or persons from damage caused for example by impacts due to rough handling or crashes. We were able to show how the mechanical properties of metal foam based components can be improved by altering their structure on various hierarchical levels inspired by features and principles important for the impact and/or puncture resistance of the biological role models, rather than by tuning the properties of the bulk material. For this various investigation methods have been established which combine mechanical testing with different imaging methods, as well as with in situ and ex situ mechanical testing methods. Different structural hierarchies especially important for the mechanical deformation and failure behaviour of the biological role models, pomelo fruit (Citrus maxima) and Macadamia integrifolia, were identified. They were abstracted and transferred into corresponding structural principles and thus hierarchically structured bio-inspired metal foams have been designed. A production route for metal based bio-inspired structures by investment casting was successfully established. This allows the production of complex and reliable structures, by implementing and combining different hierarchical structural elements found in the biological concept generators, such as strut design and integration of fibres, as well as by minimising casting defects. To evaluate the structural effects, similar investigation methods and mechanical tests were applied to both the biological role models and the metallic foams. As a result an even deeper quantitative understanding of the form-structure-function relationship of the biological concept generators as well as the bio-inspired metal foams was achieved, on deeper hierarchical levels and overarching different levels.

Discontinuous thinning in active microrheology of soft complex matter.

Employing theory and numerical simulations, we demonstrate discontinuous force thinning due to the driven motion of an external probe in a host medium. We consider two cases: an ideal structureless medium (modeling ultrasoft materials such as polymer melts) and a dilute bath of interacting repulsive particles. When the driving of the probe exceeds a critical force, the microviscosity of the medium drops abruptly by about an order of magnitude. This phenomenon occurs for strong attractive interactions between a large probe and a sufficiently dense host medium.

A review of selected pumping systems in nature and engineering--potential biomimetic concepts for improving displacement pumps and pulsation damping.

The active transport of fluids by pumps plays an essential role in engineering and biology. Due to increasing energy costs and environmental issues, topics like noise reduction, increase of efficiency and enhanced robustness are of high importance in the development of pumps in engineering. The study compares pumps in biology and engineering and assesses biomimetic potentials for improving man-made pumping systems. To this aim, examples of common challenges, applications and current biomimetic research for state-of-the art pumps are presented. The biomimetic research is helped by the similar configuration of many positive displacement pumping systems in biology and engineering. In contrast, the configuration and underlying pumping principles for fluid dynamic pumps (FDPs) differ to a greater extent in biology and engineering. However, progress has been made for positive displacement as well as for FDPs by developing biomimetic devices with artificial muscles and cilia that improve energetic efficiency and fail-safe operation or reduce noise. The circulatory system of vertebrates holds a high biomimetic potential for the damping of pressure pulsations, a common challenge in engineering. Damping of blood pressure pulsation results from a nonlinear viscoelastic behavior of the artery walls which represent a complex composite material. The transfer of the underlying functional principle could lead to an improvement of existing technical solutions and be used to develop novel biomimetic damping solutions. To enhance efficiency or thrust of man-made fluid transportation systems, research on jet propulsion in biology has shown that a pulsed jet can be tuned to either maximize thrust or efficiency. The underlying principle has already been transferred into biomimetic applications in open channel water systems. Overall there is a high potential to learn from nature in order to improve pumping systems for challenges like the reduction of pressure pulsations, increase of jet propulsion efficiency or the reduction of wear.

Stochastic thermodynamics of fluctuating density fields: non-equilibrium free energy differences under coarse-graining.

We discuss the stochastic thermodynamics of systems that are described by a time-dependent density field, for example, simple liquids and colloidal suspensions. For a time-dependent change of external parameters, we show that the Jarzynski relation connecting work with the change of free energy holds if the time evolution of the density follows the Kawasaki-Dean equation. Specifically, we study the work distributions for the compression and expansion of a two-dimensional colloidal model suspension implementing a practical coarse-graining scheme of the microscopic particle positions. We demonstrate that even if coarse-grained dynamics and density functional do not match, the fluctuation relations for the work still hold albeit for a different, apparent, change of free energy.

Structure-function relationship of the foam-like pomelo peel (Citrus maxima)-an inspiration for the development of biomimetic damping materials with high energy dissipation.

The mechanical properties of artificial foams are mainly determined by the choice of bulk materials and relative density. In natural foams, in contrast, variation to optimize properties is achieved by structural optimization rather than by conscious substitution of bulk materials. Pomelos (Citrus maxima) have a thick foam-like peel which is capable of dissipating considerable amounts of kinetic energy and thus this fruit represents an ideal role model for the development of biomimetic impact damping structures. This paper focuses on the analysis of the biomechanics of the pomelo peel and on its structure-function relationship. It deals with the determination of the onset strain of densification of this foam-like tissue and on how this property is influenced by the arrangement of vascular bundles. It was found here that the vascular bundles branch in a very regular manner-every 16.5% of the radial peel thickness-and that the surrounding peel tissue (pericarp) attains its exceptional thickness mainly by the expansion of existing interconnected cells causing an increasing volume of the intercellular space, rather than by cell division. These findings lead to the discussion of the pomelo peel as an inspiration for fibre-reinforced cast metallic foams with the capacity for excellent energy dissipation.

Flectofin: a hingeless flapping mechanism inspired by nature.

This paper presents a novel biomimetic approach to the kinematics of deployable systems for architectural purposes. Elastic deformation of the entire structure replaces the need for local hinges. This change becomes possible by using fibre-reinforced polymers (FRP) such as glass fibre reinforced polymer (GFRP) that can combine high tensile strength with low bending stiffness, thus offering a large range of calibrated elastic deformations. The employment of elasticity within a structure facilitates not only the generation of complex geometries, but also takes the design space a step further by creating elastic kinetic structures, here referred to as pliable structures. In this paper, the authors give an insight into the abstraction strategies used to derive elastic kinetics from plants, which show a clear interrelation of form, actuation and kinematics. Thereby, the focus will be on form-finding and simulation methods which have been adopted to generate a biomimetic principle which is patented under the name Flectofin®. This bio inspired hingeless flapping device is inspired by the valvular pollination mechanism that was derived and abstracted from the kinematics found in the Bird-Of-Paradise flower (Strelitzia reginae, Strelitziaceae).

Characterizing potentials by a generalized Boltzmann factor.

Based on the concept of a nonequilibrium steady state, we present a method to experimentally determine energy landscapes acting on colloidal systems. By measuring the stationary probability distribution and the current in the system, we explore potential landscapes with barriers up to several hundred k_BT. As an illustration, we use this approach to measure the effective diffusion coefficient of a colloidal particle moving in a tilted potential.

Einstein relation generalized to nonequilibrium.

The Einstein relation connecting the diffusion constant and the mobility is violated beyond the linear response regime. For a colloidal particle driven along a periodic potential imposed by laser traps, we test the recent theoretical generalization of the Einstein relation to the nonequilibrium regime which involves an integral over measurable velocity correlation functions.

Measurement of stochastic entropy production.

Using fluorescence spectroscopy we directly measure entropy production of a single two-level system realized experimentally as an optically driven defect center in diamond. We exploit a recent suggestion to define entropy on the level of a single stochastic trajectory [Seifert, Phys. Rev. Lett. 95, 040602 (2005)10.1103/PhysRevLett.95.040602]. Entropy production can then be split into one of the system itself and one of the surrounding medium. We demonstrate that the total entropy production obeys various exact relations for finite time trajectories.