2011, Villmow, T., Pegel, S., John, A., Rentenberger, R., Pötschke, P.

Today polymer/carbon nanotube (CNT) composites can be found in sports equipment, cars, and electronic devices. The growth of old and new markets in this area has been stimulated by our increased understanding of relevant production and processing methods, as well as the considerable price reduction of industrial CNT grades. In particular, CNT based electrically conductive polymer composites (CPCs) offer a range of opportunities because of their unique property profile; they demonstrate low specific gravity in combination with relatively good mechanical properties and processability. The electrical conductivity of polymer/CNT composites results from a continuous filler network that can be affected by various external stimuli, such as temperature shifts, mechanical deformations, and the presence of gases and vapors or solvents. Accordingly, CNT based CPCs represent promising candidates for the design of smart components capable of integrated monitoring. In this article we focus on their use as leakage detectors for organic solvents.

2017, Staudinger, U., Zyla, G., Krause, Beate, Janke, A., Fischer, D., Esen, C., Voit, B., Ostendorf, A.

Femtosecond laser-induced two-photon polymerization (2PP) of carbon nanofiller doped polymers was utilized to produce electrically conductive microstructures, which are expected to be applicable as microelectronic components or micro-electromechanical systems in sensors. The nanocomposites were processed by compounding an inorganic-organic hybrid material with two different types (short and long) of single walled carbon nanotubes (SWCNTs). Different SWCNT contents were dispersed in the polymer by sonication to adjust the electrical conductivity of the nanocomposites. Low surface resistivity values of ~ 4.6 × 105 Ω/sq. could be measured for coated reference films with a thickness of 30 μm having an exceptionally low SWCNT content of 0.01 wt% of the long type of SWCNTs. In contrast, a higher minimum resistivity of 1.5 × 106 Ω/sq. was exhibited for composites with a higher content, 2 wt%, of short SWCNTs. The structural quality of the microstructures processed by 2PP was mainly influenced by the dispersion quality of the SWCNTs. To characterize the electrical conductivity, conductive atomic force microscopy was applied for the first time. In microstructures with 0.05 wt% of the long type of SWCNTs, a contact current could be detected over a wide range of the measured area visualizing the electrical conductive CNT network, which has not been reported before.

2012, Alig, I., Pötschke, P., Lellinger, D., Skipa, T., Pegel, S., Kasaliwal, G.R., Villmow, T.

As for nanofillers in general, the properties of carbon nanotube (CNT) -polymer composites depend strongly on the filler arrangement and the structure of the filler network. This article reviews our actual understanding of the relation between processing conditions, state of CNT dispersion and structure of the filler network on the one hand, and the resulting electrical, melt rheological and mechanical properties, on the other hand. The as-produced rather compact agglomerates of CNTs (initial agglomerates, >1 μm), whose structure can vary for different tube manufacturers, synthesis and/or purification conditions, have first to be well dispersed in the polymer matrix during the mixing step, before they can be arranged to a filler network with defined physical properties by forming secondary agglomerates. Influencing factors on the melt dispersion of initial agglomerates of multi-walled CNTs into individualized tubes are discussed in context of dispersion mechanisms, namely the melt infiltration into initial agglomerates, agglomerate rupture and nanotube erosion from agglomerate surfaces. The hierarchical morphology of filler arrangement resulting from secondary agglomeration processes has been found to be due to a competition of build-up and destruction for the actual melt temperature and the given external flow field forces. Related experimental results from in-line and laboratory experiments and a model approach for description of shear-induced properties are presented.

2011, Aryasomayajula, A., Perike, S., Hensel, R., Posseckardt, J., Gerlach, G., Funk, R.H.W.

Ionic membrane currents play an important role during regeneration of nerve cells, embryonic development and wound healing processes. Measuring the intracellular ion currents across the cell membrane is important in understanding the cellular functions related to the ion activities. A novel patch micro electrode array (p-MEA) for measuring the ionic membrane currents without poisoning the cells due to emitting metal ions is described in this paper. Results on biocompatibility of the device are presented. We discuss the fabrication and working principle of p-MEA.

2014, Ionov, L.

The rapid development of microtechnology in recent times has increased the necessity for the development of devices, which are able to perform mechanical work on the micro- and macroscale. Among all kinds of actuators, the ones based on stimuli-responsive hydrogels, which are three-dimensional polymer networks strongly imbibed with water, deserve particular attention. This paper aims to provide a brief overview of stimuli-responsive hydrogel actuators with respect to their sensitivity to different stimuli, different kinds of deformation, the possibilities of generating different types of movement, as well as their applications.

2011, Schulz, V., Zschoche, S., Zhang, H.P., Voit, B., Gerlach, G.

Within this work we present the synthesis and characterization of a pH-sensitive macroporous p(AAm-co-AA) hydrogel with an interconnected channel structure to enhance diffusion of aqueous solutions. The hydrogel is characterized by SEM and mercury porosimetry. Furthermore, the hydrogel is successfully integrated into piezoresistive microsensors measuring the hydrogel swelling due to pH changes. A response time reduction of about 80% compared to sensors with conventional non-porous hydrogels is accomplished.