Danja Voges

Structural Characterization of the Whisker System of the Rat

Vibrissae or tactile hairs, commonly known as whiskers, are the mechanical gates of special mechano-sensitive organs. In terrestrial mammals, they carry various functions, especially object determination and texture discrimination. We hypothesise that the characteristic morphology and structure of whiskers is a primary morphological condition for their mechano-sensitive functions. To constitute mathematical models on the systematic but different mechanical behavior of the main types of whisker hairs (micro vibrissae, macro vibrissae, straddlers), information is lacking on the distribution of properties in a field of all three types of hairs, taken from one and the same animal. Referring to sets taken from five individuals, geometry data is provided as one complete set for a female rat (Rattus norvegicus). Due to measurements of diameters along the length, the shape of whiskers in rats is confirmed to resemble a cone, which may be overlaid by some convexity or concavity. Additionally, the surface and internal structure of different vibrissae were examined by scanning electron microscopy. The cuticle of the rat whisker consists of flat scales, overlapping like roofing slates. A cross section reveals up to 20 superposed layers of cuticular scales. The longitudinal dimension of one scale is shorter in whiskers compared with body hairs. A hollow medulla is observed from the base to approximately half of the overall length, which is then partially filled by compact tissue, until it disappears completely near the tip. An extraordinarily thick cortex probably rules the characteristic bending features, and the multilayer cuticle probably has a mainly protective function.

Characterizing the Substrate Contact of Carpal Vibrissae of Rats during Locomotion

Excitation of sensors triggered by carpal vibrissae has an influence on the kinematics of legs during locomotion of rats. Via motion studies, anatomic and mechanical characterization of vibrissae – especially in the contact period with the substrate – we try to gain a better understanding of the adaptability of those special sensory organs. This knowledge might lead to new approaches for passive sensor systems in robot locomotion or other tactile tasks.

Integration of 3-D cell cultures in fluidic microsystems for biological screenings

A life support system for the cultivation of adherent 2‐D and scaffold‐based 3‐D cell cultures in a microfluidic device, a Bio‐Micro‐Electro‐Mechanical System (BioMEMS) is presented. The miniaturization level and system set‐up allow incubator‐independent operation modes and long‐term experiments with real‐time microscope observation. A dedicated seeding procedure for adherent cells into the microstructures is one key issue of the BioMEMS developed. Several seeding methods for the cells were evaluated. Biocompatibility of all materials, surfaces and methods could be demonstrated. First experiments with several cell types show the feasibility of the approach employing standard laboratory protocols. At present, the modular design and set‐up offer a broad application spectrum as well as its future extension to e.g. cultivation of other cell types, coupled cultivation chambers and the implementation of other manipulation or analysis components.

Cell cultures in microsystems: biocompatibility aspects.

Bio‐Micro‐Electro‐Mechanical Systems (BioMEMS) are a new tool in life sciences, supporting cell biology research by providing reproducible and miniaturized experimental platforms. In order to cultivate cells in such systems, appropriate microenvironmental conditions are required. Due to the multitude and variety of microbioreactors and cultivated cell types available, standardized cell handling methods and comprehensive biocompatibility data are sparse. The bioreactor developed at Ilmenau University of Technology features BioMEMS consisting of silicon, glass, and polymers, supplied by peripheral components. To verify the systems suitability for cell cultivation, it was necessary to prove whether materials and surfaces are biocompatible. Custom‐tailored biocompatibility test procedures along with adequate cell seeding and handling methods had to be developed. According to this, proper positive and negative control samples had to be identified. The cultivation procedures were carried out using osteoblast‐like murine fibroblasts (MC3T3‐E1) and primary human osteoblasts (hOB). We could provide evidence that cultivation of these cells in our BioMEMS is feasible. In this context the relevant materials and the systems structure can be regarded as to be biocompatible. We could show that cell seeding and handling methods possess a strong impact on growth, development, and cellular activity of cell cultures in BioMEMS. Statistical biocompatibility data for the materials used is given. Biotechnol. Bioeng. 2011; 108:687–693.

Microsystems for the Characterization of 3D-ECM Analogous Bio-Interfaces

Characteristics of scaffold materials for tissue engineering have to be adapted to the respective cell lines. Especially cartilage cells require an artificial 3-dimensional extra cellular matrix, to behave and grow like in natural environment. To reach this goal, biomaterials have to be developed that fulfill these requirements. A novel structuring technique for degradable polymer scaffolds is 2-photonpolymerization. For defining best chemical and geometrical properties a microsystem is necessary that can be used as a test-environment in cell-cultivation-experiments. In this paper we describe both materials for and the process of 2-photonpolymerization. We introduce a silicon-glass-micro system with scaffold integration option for testing of scaffold materials and structures.

Biomechatronics is not just biomimetics

The idea of biomechatronics is based on the observation, that for mechatronic as well as for living systems a high degree of functional integration is characteristic. This allows biomimetic approaches without logical constraints. On the other hand, modularization is a major strength of mechatronics, while in life sciences “module” is a functional abstraction (e.g. the columns in the visual cortices of brains) with mostly diffuse structural boundaries. In practice, those contradictions turn out to be only of theoretical relevance, since biomechatronics is a strategy to gain better technical solutions, which has to be evaluated by its results, it is no ideology. For bio-robotics, the biomimetic principles of intensive use of compliance and of massive under-actuation may well be embodied in modular structures, providing integrated functions.

Theoretical and Experimental Investigations of Amoeboid Movement and First Steps of Technical Realisation

We report about the investigation of the amoeboid locomotion at Amoeba proteus. Based on the detailed experimental study of the internal cytoplasm flow and the variation of the contour of the amoeba with optical flow measurement techniques like particle image velocimetry (PIV) we found characteristic velocity fields and motions of the center of mass. Furthermore a peripheral cell model is developed, in which a contractile backward flow of actin-myosin in the cortex stabilizes cell polarity and locomotion by inducing more protrusions in the front and stronger retraction in the rear. The results from the experimental and theoretical study were used to realise prototypes of locomotion systems, composed of silicon elastomer body with controlled elasticity and driven by a magnetic system, based on amoeboid motion principles.

Bio-Microsystem for Cell Cultivation and Manipulation and its Peripherals

The smart combination of silicon, glass and polymers offers microenvironments with properties applicable to cultivation, observation and manipulation of cells. Function modules of the system and a concept for their use in the laboratory as well as the combination with adapted peripheral devices form such platforms for cell and biocompatibility analyses and cell breeding. Requirements for the design of these modular microsystems and its auxiliary components determine the main components of the cultivation and manipulation system which are introduced in this paper.