Design of a parallel robot with additively manufactured flexure hinges for a cryogenic work environment

Automation is ubiquitous in today's industrial landscape and is finding its way into more and more highly specialised applications - also in the field of cryopreservation. The extreme work conditions in cryobanks place exceptionally high demands on the mechanical and electronic components used. The preservation and storage of biological samples take place at temperatures between -130 °C and -196 °C using liquid nitrogen as a cooling medium. The bearings and joints used in industrial parallel kinematic robots (for example, ball bearings or Cardan joints) jam at these ambient parameters and are unsuitable for an application within a cryobank. We, therefore, develop methods and technologies to enable fully automated handling of biological samples under cryogenic working conditions. The basis for this is a parallel kinematic robot structure that allows the drives to be placed outside the cold environment. In contrast, the rest of the robot structure can be actuated in a cryogenic container. In this context, the passive joints for this parallel robot are designed as additively manufactured monolithic flexure hinges. This paper presents the design, simulation, and construction of the parallel robot and focuses on the flexure hinges fabricated using the selective laser melting process (SLM). We describe the design of the flexure hinges, their intended use in the robot, and the experimental setup used for their validation. We also compare the operating parameters recorded in experiments (such as bending angle, bending moment) with the data obtained in finite element method simulations (FEM). In addition, we describe the geometric constraints and deviations of the manufactured joints due to the manufacturing process

Induktive Energieübertragung in eine kryogene Umgebung : Design und Charakterisierung einer drahtlosen Energieübertragungsstrecke für den Betrieb einer Greiferaktorik

In der Forschung und Industrie ist die Automatisierung allgegenwärtig und findet ihren Weg in immer mehr hochspezialisierte Anwendungen - einschließlich der Kryokonservierung. Dennoch ist die manuelle Handhabung von biologischen oder toxischen Proben in wissenschaftlichen und kommerziellen Lagereinrichtungen immer noch vorherrschend. Dies bedingt für das Personal ein erhebliches Verletzungsrisiko durch Kälteverbrennungen. Darüber hinaus wird die Unversehrtheit der Proben durch Temperaturschwankungen oder Verunreinigungen gefährdet. In diesem Beitrag wird ein Ansatz für die Automatisierung von Handhabungsprozessen bei tiefen Tem-peraturen zwischen -130 °C und -190 °C in Kryobanken vorgestellt. Das Automatisierungssystem basiert auf einem Parallelroboter, da seine Struktur die Positionierung der Antriebe außerhalb des gekühlten Arbeitsraums erlaubt. Die Gelenke und Manipulatoren des Roboters befinden sich innerhalb des kroygenen Lagerbehälters, der mit flüssigem Stickstoff gekühlt wird. Die Energieversorgung der kryotauglichen Greiferaktorik im Inneren des Lagerbehälters erfolgt induktiv. Zu diesem Zweck wurden Varianten von Spulendesigns und deren Anordnung mit der FEM-Software ANSYS unter Einbeziehung von applikationsspezifischen Randbedingungen modelliert. Die Dimensionierung der Schwingkreise wurde mit Berechnungen in Mathcad ergänzend durchgeführt. Die entwickelte Greiferaktorik lässt sich in flüssigem Stickstoff mit einem Wirkungsgrad von etwa 86% bei einem Spulen-abstand von 9,5 cm und noch mit etwa 10% Wirkungsgrad bei einem Spulenabstand von 33,5 cm betreiben

Roboterkomponenten für den kryogenen Arbeitsraum : Entwicklung von Festkörpergelenken und monolithischen Greifersystemen für eine Parallelroboterstruktur

In der heutigen Industrie ist die Automatisierung ein allgegenwärtiger Faktor, selbst in Nischenanwendungen wie der Kryokonservierung. Die manuelle Handhabung von biologischen oder toxischen Proben ist in Forschungseinrichtungen immer noch die Norm. Die Konservierung und Lagerung solcher Proben erfolgt in sogenannten Kryobanken bei Temperaturen zwischen -130 °C und -196 °C. In heute üblichen Kryobanken werden die Proben oft mit sperriger Schutzkleidung von Hand ein- und ausgelagert oder bewegt. Dies ist notwendig, da ein erhebliches Verletzungsrisiko für den Arbeiter durch Kälteverbrennungen sowie eine Gefährdung der Probenintegrität durch Beschädigung und Erwärmung oder auch Temperaturwechsel besteht. Zur Überwindung dieser Probleme ist eine Vollautomatisierung bei Temperaturen unter -130 °C wünschenswert. In diesem Beitrag wird das von der DFG geförderte Projekt "Methoden zur Automatisierung von Handhabungsprozessen unter kryogenen Umgebungs-bedingungen" vorgestellt und erläutert. Dabei wird besonders auf die Teilaspekte der Greifertechnologie sowie der Optimierung der verwendeten Festkörpergelenke eingegangen

A measurement setup and automated calculation method to determine the charge injection capacity of implantable microelectrodes

Producción CientíficaThe design of safe stimulation protocols for functional electrostimulation requires knowledge of the “maximum reversible charge injection capacity” of the implantable microelectrodes. One of the main difficulties encountered in characterizing such microelectrodes is the calculation of the access voltage Va. This paper proposes a method to calculate Va that does not require prior knowledge of the overpotential terms and of the electrolyte (or excitable tissue) resistance, which is an advantage for in vivo electrochemical characterization of microelectrodes. To validate this method, we compare the calculated results with those obtained from conventional methods for characterizing three flexible platinum microelectrodes by cyclic voltammetry and voltage transient measurements. This paper presents the experimental setup, the required instrumentation, and the signal processing.Ministerio de Economía y Competitividad ( Research project DPI2016-80391-C3-3-R

Monitoring System for Laboratory Mice Transportation: A Novel Concept for the Measurement of Physiological and Environmental Parameters

Laboratory mice are used in biomedical research as “models” for studying human disease. These mice may be subject to significant levels of stress during transportation that can cause alterations that could negatively affect the results of the performed investigation. Here, we present the design and realization of a prototypical transportation container for laboratory mice, which may contribute to improved laboratory animal welfare. This prototype incorporates electric potential integrated circuit (EPIC) sensors, which have been shown to allow the recording of physiological parameters (heart rate and breathing rate) and other sensors for recording environmental parameters during mouse transportation. This allows for the estimation of the stress levels suffered by mice. First experimental results for capturing physiological and environmental parameters are shown and discussed

Capacitive Sensing for Non-Invasive Breathing and Heart Monitoring in Non-Restrained, Non-Sedated Laboratory Mice

Animal testing plays a vital role in biomedical research. Stress reduction is important for improving research results and increasing the welfare and the quality of life of laboratory animals. To estimate stress we believe it is of great importance to develop non-invasive techniques for monitoring physiological signals during the transport of laboratory animals, thereby allowing the gathering of information on the transport conditions, and, eventually, the improvement of these conditions. Here, we study the suitability of commercially available electric potential integrated circuit (EPIC) sensors, using both contact and contactless techniques, for monitoring the heart rate and breathing rate of non-restrained, non-sedated laboratory mice. The design has been tested under different scenarios with the aim of checking the plausibility of performing contactless capture of mouse heart activity (ideally with an electrocardiogram). First experimental results are shown

Experimental Characterization of Ferroelectric Capacitor Circuits for the Realization of Simply Designed Electroceuticals

Currently, a large number of neurostimulators are commercially available for the treatment of drug-resistant diseases and as an alternative to pharmaceuticals. According to the current state of the art, such highly engineered electroceuticals require bulky battery units and necessitate the use of leads and extensions to connect the implantable electronic device to the stimulation electrodes. The battery life and the use of wired electrodes constrain the long-term use of such implantable systems. Furthermore, for therapeutic success and patient safety, it is of utmost importance to keep the stimulation current within a safe range. In this paper, we propose an implantable system design that consists of a low number of passive electronic components and does not require a battery. The stimulation parameters and power are transmitted inductively using an extracorporeal wearable transmitter at frequencies below 1 MHz. A simple circuit design approach is presented to achieve a closed-loop control of the stimulation current by exploiting the nonlinear properties of ferroelectric materials in ceramic capacitors. Twenty circuit topologies of series- and/or parallel-connected ceramic capacitors are investigated by measurement and are modeled in Mathcad. An approximately linear increase in the stimulation current, a stabilization of the stimulation current and an unstable state of the system were observed. In contrast to previous results, specific plateau ranges of the stimulation current can be set by the investigated circuit topologies. For further investigations, the consistency of the proposed model needs to be improved for higher induced voltage ranges

Physics-Based Modeling of Ferroelectric Hysteresis for Ceramic Capacitors in Inductively Coupled Microstimulators

In this article, we present a physics-based model for nonlinear and hysteretic ferroelectric capacitors in inductively coupled microstimulator circuits. The purpose of this model is to predict the system’s dynamic response as a function of the dielectric material properties, with the aim of optimizing the performance in passive power control applications.We describe the workflow starting from the extraction of the dielectric material properties of commercial ceramic capacitors to the implementation into the physicsbased model of the overall circuit. Selected capacitors were experimentally characterized at frequencies above 100 kHz by means of both small signals (5 mVrms, ±25 Vdc, and ±40 Vdc) and large signals (±25 Vac and ±40 Vac). Our results show that the developed model is well suited for accurately predicting the circuit’s stimulation current for highly nonlinear capacitors and exhibits higher precision compared to commonly used models based on differential capacitance. Preliminary in vitro measurement results are finally described to provide proof of concept of the envisioned model-based passive power control in implantable microstimulators

On-line anxiety level detection from biosignals: Machine learning based on a randomized controlled trial with spider-fearful individuals.

We present performance results concerning the validation for anxiety level detection based on trained mathematical models using supervised machine learning techniques. The model training is based on biosignals acquired in a randomized controlled trial. Wearable sensors were used to collect electrocardiogram, electrodermal activity, and respiration from spider-fearful individuals. We designed and applied ten approaches for data labeling considering individual biosignals as well as subjective ratings. Performance results revealed a selection of trained models adapted for two-level (low and high) and three-level (low, medium and high) classification of anxiety using a minimal set of six features. We obtained a remarkable accuracy of 89.8% for the two-level classification and of 74.4% for the three-level classification using a short time window length of ten seconds when applying the approach that uses subjective ratings for data labeling. Bagged Trees proved to be the most suitable classifier type among the classification models studied. The trained models will have a practical impact on the feasibility study of an augmented reality exposure therapy based on a therapeutic game for the treatment of arachnophobia