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1. Training performance of Nb3Sn Rutherford cables in a channel with a wide range of impregnation materials

Author

Otten, S., Kario, A., Leferink, W. A. J. Wessel. J., Kate, H. H. J. ten, Daly, M., Hug, C., Sidorov, S., Brem, A., Auchmann, B., Studer, P., and Tervoort, T.

Subjects
Physics - Accelerator Physics
Abstract

Training of accelerator magnets is a costly and time consuming process. The number of training quenches must therefore be reduced to a minimum. We investigate training of impregnated Nb3Sn Rutherford cable in a small-scale experiment. The test involves a Rutherford cable impregnated in a meandering channel simulating the environment of a canted-cosine-theta (CCT) coil. The sample is powered using a transformer and the Lorentz force is generated by an externally applied magnetic field. The low material and helium consumption enable the test of a larger number of samples. In this article, we present training of samples impregnated with alumina-filled epoxy resins, a modified resin with paraffin-like mechanical properties, and a new tough resin in development at ETH Z\"urich. These new data are compared with previous results published earlier. Compared to samples with unfilled epoxy resin, those with alumina-filled epoxy show favorable training properties with higher initial quench currents and fewer training quenches before reaching 80% of the critical current., Comment: 4 pages, 6 figures. Submitted to IEEE Transactions on Applied Superconductivity (TAS) for publication in the ASC2022 special issue. Copyright of the article was transferred to IEEE by submission

Published
2022

2. The 16 T Dipole Development Program for FCC and HE-LHC

Author

Schoerling, D, Arbelaez, D, Auchmann, B, Bajko, M, Ballarino, A, Barzi, E, Bellomo, G, Benedikt, M, Bermudez, SI, Bordini, B, Bottura, L, Brouwer, L, Bruzzone, P, Caiffi, B, Caspi, S, Chakraborti, A, Coatanea, E, De Rijk, G, Dhalle, M, Durante, M, Fabbricatore, P, Farinon, S, Felice, H, Fernandez, A, Fernandez, IS, Gao, P, Gold, B, Gortsas, T, Gourlay, S, Juchno, M, Kashikhin, V, Kokkinos, C, Kokkinos, S, Koskinen, K, Lackner, F, Lorin, C, Loukas, K, Louzguiti, A, Lyytikainen, K, Mariotto, S, Marchevsky, M, Montenero, G, Munilla, J, Novitski, I, Ogitsu, T, Pampaloni, A, Perez, JC, Pes, C, Petrone, C, Polyzos, D, Prestemon, S, Prioli, M, Ricci, AM, Rifflet, JM, Rochepault, E, Russenschuck, S, Salmi, T, Santillana, IA, Savary, F, Scheuerlein, C, Segreti, M, Senatore, C, Sorbi, M, Statera, M, Stenvall, A, Tavian, L, Tervoort, T, Tommasini, D, Toral, F, Valente, R, Velev, G, Verweij, AP, Wessel, S, Wolf, F, Zimmermann, F, and Zlobin, AV

Subjects
FCC, Nb3Sn, superconducting, T, General Physics, Electrical and Electronic Engineering, Condensed Matter Physics, Materials Engineering
Abstract

A future circular collider (FCC) with a center-of-mass energy of 100 TeV and a circumference of around 100 km, or an energy upgrade of the LHC (HE-LHC) to 27 TeV require bending magnets providing 16 T in a 50-mm aperture. Several development programs for these magnets, based on Nb3Sn technology, are being pursued in Europe and in the U.S. In these programs, cos-theta, block-type, common-coil, and canted-cos-theta magnets are explored; first model magnets are under manufacture; limits on conductor stress levels are studied; and a conductor with enhanced characteristics is developed. This paper summarizes and discusses the status, plans, and preliminary results of these programs.

Published
2019

6. Training Curves of Nb3Sn Rutherford Cables With a Wide Range of Impregnation Materials Measured in the BOX Facility

Author

Otten, S., Kario, A., Wessel, W. A. J., Leferink, J., Ten Kate, H. H. J., Daly, M., Hug, C., Sidorov, S., Brem, A., Auchmann, B., Studer, P., and Tervoort, T.

Abstract

Training of accelerator magnets is a costly and time consuming process. The number of training quenches must therefore be reduced to a minimum. We investigate training of impregnated Nb3Sn Rutherford cable in a small-scale experiment named BOX (BOnding Experiment). The test involves a Rutherford cable impregnated in a meandering channel simulating the environment of a canted-cosine-theta (CCT) coil. The sample is powered using a transformer and the Lorentz force is generated by an externally applied magnetic field. The low material and helium consumption enable the test of a larger number of samples. In this article, we present training of samples impregnated with alumina-filled epoxy resins, a modified resin with paraffin-like mechanical properties, and a new tough resin in development at ETH Zürich. These new data are compared with previous results published earlier. Compared to samples with unfilled epoxy resin, those with alumina-filled epoxy show favorable training properties with higher initial quench currents and fewer training quenches before reaching 80% of the critical current.

Published
2023
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11. Surface viscoelasticity in model polymer multilayers: From planar interfaces to rising bubbles

Author

Pepicelli, M., Jaensson, N., Tregouët, C., Schroyen, B., Alicke, A., Tervoort, T., Monteux, C., Vermant, J., Pepicelli, M., Jaensson, N., Tregouët, C., Schroyen, B., Alicke, A., Tervoort, T., Monteux, C., and Vermant, J.

Abstract

In the present work, a polymeric transient viscoelastic network is used as a model system to investigate several fundamentals of interfacial viscoelasticity and nonlinear behavior, in simple shear, compression, and for simple mixed deformations. A supramolecular polymer bilayer, characterized by long but finite relaxation times, is created at the water-air interface using a layer-by-layer assembly method. The possibility of studying the individual layers starting from an unstrained reference state enabled the independent quantification of the equilibrium thermodynamic properties, and the viscoelastic response of the bilayer could be studied separately for shear and compressional deformations. Time- and frequency-dependent material functions of the layer were determined in simple shear and uniform compression. Moreover, a quasilinear neo-Hookean model for elastic interfaces was adapted to describe step strain experiments on a viscoelastic system by allowing the material properties to be time-dependent. The use of this model made it possible to calculate the response of the system to step deformations. Within the linear response regime, both stress-strain proportionality and the superposition principle were investigated. Furthermore, the onset of nonlinear behavior of the extra stresses was characterized in shear and for the first time in pure compression. We conclude by investigating the multilayer system in a rising bubble setup and show that the neo-Hookean model is able to predict the extra and deviatoric surface stresses well up to moderate deformations.

Published
2019

12. Continuum damage mechanics: combining thermodynamics with a thoughtful characterization of the microstructure

Author

Hütter, M., Tervoort, T., Hütter, M., and Tervoort, T.

Abstract

We formulate a macroscopic description of the mechanics of damaged materials. To represent the microstructure, the distribution of crack sizes is captured by way of the Minkowski functionals, or so-called quermass integrals, while a second-rank tensor is used to describe the average orientation of the cracks. A two phase-type approach is adopted to distinguish elastically strained material from unstrained regions in the wake of the cracks. Using nonequilibrium thermodynamic techniques, the driving force for the growth of the microcracks is naturally identified. In particular, Griffith's law is generalized to assemblies of polydisperse crack sizes. Due to the detailed characterization of the microstructure, we are also able to account for the plastic zones at the rims of the cracks that are known to hamper the crack growth, and to discuss possible forms of the damage parameter. The presented approach separates in a transparent fashion the incorporation of fundamental thermodynamic and mechanic principles on one hand, from the specification of the material and details of the crack formation and growth on the other hand

Published
2018

13. A simple method for the determination of refractive indices of (rough) transparent solids

Author

Nussbaumer, R., Halter, M., Tervoort, T., Caseri, W., Smith, P., Nussbaumer, R., Halter, M., Tervoort, T., Caseri, W., and Smith, P.

Abstract

Simple methods for the determination of refractive indices of transparent polymers and inorganic and organic solids of irregular geometry or with scratched or corrugated surfaces are rare. A classical procedure is based on the invisibility of a body immersed in a liquid with the same refractive index as that of the body. In order to avoid the laborious procedure connected with the search for a liquid with matching refractive index and to find an approach which is independent of the observation by eye, we describe here a modified immersion method which allows the ready determination of the refractive index of solids. The present method is based on the interpolation of the maximum transmission (nTmax) of a solid immersed in liquids with different, typically non-matching, refractive indices. Illustrations with quartz glass, crown glass and poly(vinylidene fluoride) (PVDF) films showed that nTmax can be determined with a reproducibility of ± 0.003. By comparison with refractive indices determined by ellipsometry, it was concluded that the refractive index of a solid can be determined with the modified immersion method within an accuracy better than ± 0.01 when systematic errors resulting from the fit method are also taken into consideration

Published
2018

14. A Protocol Specification Language for Testing Implementations

Author

Tervoort, T., Prasetya, dr. S.W.B. (Thesis Advisor), Tervoort, T., and Prasetya, dr. S.W.B. (Thesis Advisor)

Abstract

When developing a system that partakes in a communication protocol, testing whether the implementation conforms to the official specification of that protocol is difficult: the specification may be unclear or ambiguous and creating a simulator that automates tests is time-consuming. The protocol specification language APSL is proposed, with which one can describe the types of messages used in a protocol, along with a model of the protocol’s state machine. It distinguishes itself from similar languages by allowing the generation of message parsers and serializers, and by providing an interaction model useful for conformance testing. Additionally, an extensible framework is presented that can execute automatic conformance tests in order to determine whether an implemen- tation exhibits the behaviour expressed by an APSL specification.

Published
2016

15. The effect of size and density on the mean retention time of particles in the reticulorumen of cattle (Bos primigenius f. taurus), muskoxen (Ovibos moschatus) and moose (Alces alces)

Author

Clauss, Marcus, Lechner, I, Barboza, P, Collins, W, Tervoort, T A, Südekum, K H, Codron, Daryl, Hummel, J, University of Zurich, and Clauss, Marcus

Subjects
10253 Department of Small Animals, Particle retention, 630 Agriculture, Rumen physiology, Viscosity, Stratification, Particle size, Fluid throughput, 570 Life sciences, biology, 2916 Nutrition and Dietetics, 2701 Medicine (miscellaneous)
Abstract

British Journal of Nutrition, 105 (4), ISSN:0007-1145, ISSN:1475-2662

Published
2011

16. The effect of size and density on the mean retention time of particles in the reticulorumen of cattle ( Bos primigenius f. taurus), muskoxen ( Ovibos moschatus) and moose ( Alces alces)

Author

Clauss, Marcus; https://orcid.org/0000-0003-3841-6207, Lechner, I, Barboza, P, Collins, W, Tervoort, T A, Südekum, K H, Codron, Daryl; https://orcid.org/0000-0001-5223-9513, Hummel, J, Clauss, Marcus; https://orcid.org/0000-0003-3841-6207, Lechner, I, Barboza, P, Collins, W, Tervoort, T A, Südekum, K H, Codron, Daryl; https://orcid.org/0000-0001-5223-9513, and Hummel, J

Abstract

Particle passage from the reticulorumen (RR) depends on particle density and size. Forage particle density and size are related and change over time in the RR. Particle density mainly influences sorting in the reticulum, whereas particle size influences particle retention in the fibre mat of stratified rumen contents (‘filter-bed’ effect). We investigated these effects independently, by inserting plastic particles of different sizes (1, 10 and 20mm) and densities (1·03, 1·20 and 1·44 mg/ml) in the RR of cattle (Bos primigenius f. taurus) as a pilot study, and of muskoxen (Ovibos moschatus; n 4) and moose (Alces alces; n 2) both fed two diets (browse and grass). Faeces were analysed for plastic residues for 13 d after dosing to calculate mean retention times (MRT). The results confirmed previous findings of differences in absolute MRT between species. Comparing muskoxen with moose, there was no difference in the effect of particle density on the MRT between species but particle size had a more pronounced effect on the MRT in muskoxen than in moose. This indicated a stronger ‘filter-bed effect’ in muskoxen, in accord with the reports of stratified RR contents in this species v. the absence of RR content stratification in moose. Low-density particles were retained longer in both species fed on grass diets, indicating a contribution of forage type to the ‘filter-bed effect’. The results indicate that retention based on particle size may differ between ruminant species, depending on the presence of a fibre mat in the RR, whereas the density-dependent mechanism of sedimentation in the RR is rather constant across species.

Published
2011

30. Mechanical Properties of Sorbitol-Clarified Isotactic Polypropylene:  Influence of Additive Concentration on Polymer Structure and Yield Behavior

Author

Kristiansen, M., Tervoort, T., Smith, P., and Goossens, H.

Abstract

The solid-state structure and yield behavior of isotactic polypropylene (i-PP) containing the nucleating/clarifying agent 1,3:2,4-bis(3,4-dimethylbenzylidene)sorbitol (DMDBS) was investigated in the additive concentration range 0−1 wt %. The raise of the crystallization temperature of i-PP caused by addition of 0.2 wt % and more of the additive led to an increase in the polymer lamellar thickness, which, in turn, resulted in an increase of the yield stress at constant aging time. Both the strain-rate dependence of the yield stress and the rate of increase of the yield stress upon physical aging of compression-molded samples were not influenced by the addition of DMDBS. Analysis of the experimental data by means of the Eyring theory for thermally activated processes resulted in an average shear activation volume of 2.21 nm3. The dependence of the yield stress on the additive concentration was in gratifying agreement with the previously reported monotectic phase behavior of the i-PP/DMDBS system.

Published
2005

31. The Binary System Isotactic Polypropylene/Bis(3,4-dimethylbenzylidene)sorbitol:  Phase Behavior, Nucleation, and Optical Properties

Author

Kristiansen, M., Werner, M., Tervoort, T., Smith, P., Blomenhofer, M., and Schmidt, H.-W.

Abstract

The phase behavior of the binary system consisting of the commercial nucleating and clarifying agent 1,3:2,4-bis(3,4-dimethyldibenzylidene)sorbitol (DMDBS, Millad 3988) and isotactic polypropylene (i-PP) was investigated over the entire concentration range by means of differential scanning calorimetry (DSC), rheology, and optical microscopy. Experimental phase diagrams were constructed from data obtained in melting and crystallization studies, and a simple binary monotectic is advanced. Distinct regimes in the phase diagram, which apparently dictate nucleation and clarification of i-PP by DMDBS, are discussed. A maximum increase in the crystallization temperature of i-PP due to the nucleating action of DMDBS was observed in compositions containing between 0.2 and 1 wt % of the latter. Liquid−liquid phase separation was observed at elevated temperatures for i-PP/DMDBS mixtures comprising more than 2 wt % of DMDBS. A study of the optical properties of the i-PP/DMDBS system revealed that values for haze and clarity of injection-molded plaques progressively decreased and increased, respectively, in the concentration range between 0.2 and 1 wt % DMDBS in i-PP; at DMDBS concentrations exceeding 1 wt % the presence of the additive had an adverse effect on the optical properties of i-PP. Finally, a surprisingly strong influence of cooling kinetics on the phase behavior and, consequently, on the optical properties of the i-PP/DMDBS system was detected, which is of obvious relevance for industrial applications.

Published
2003

32. On Abrasive Wear of Polyethylene

Author

Tervoort, T. A., Visjager, J., and Smith, P.

Abstract

Despite widespread and growing use of polymers in applications where abrasion is present, ranging from gearboxes to prosthetic joints, abrasive wear of these materials is ill-understood. We present a study that for commercially relevant polyethylene (PE) points to the effective number of physical cross-links per macromolecular chain as the principal&sbd;remarkably simple&sbd;factor that dictates the intrinsic abrasive wear resistance. This new insight has permitted us, among other things, to identify a polyethylene of a hereto unknown matrix of desirable properties, i.e., ultra-wear-resistant and&sbd;unlike the commonly used ultrahigh molecular weight version (UHMW PE)&sbd;melt-processable, which should open a host of novel applications.

Published
2002
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33. Melt-Processable Poly(tetrafluoroethylene)

Author

Tervoort, T., Visjager, J., Graf, B., and Smith, P.

Abstract

The identification of a window of viscosities of poly(tetrafluoroethylene)s is described that permits standard melt-processing of this unique polymer into mechanically coherent, tough objects&sbd;a polymer that, heretofore, has been characterized as “intractable” and “not melt-processable”.

Published
2000

34. From Vauquelin's and Magnus' Salts to Gels, Uniaxially Oriented Films, and Fibers:  Synthesis, Characterization, and Properties of Tetrakis(1-aminoalkane)metal(II) Tetrachlorometalates(II)

Author

Bremi, J., Brovelli, D., Caseri, W., Hahner, G., Smith, P., and Tervoort, T.

Abstract

Complexes of the type [Pt(NH2R)4][PtCl4] with R = (CH2)nCH3, where n is 3, 6, 7, 8, 9, 11, or 13, were synthesized and characterized with various methods (e.g., IR spectroscopy, SAXS, XPS, NEXAFS, TEM, DSC, and TGA). For comparison, the classical Magnus' green and pink salt (where R = H) were also prepared. The designated alkyl-substituted platinum compounds are pink, but their structure seems to be related rather with Magnus' green than with the pink salt. However, the Pt−Pt distance in the pink alkyl-substituted compounds is most likely larger than in Magnus' green salt. This result is in agreement with the low electrical conductivity (<10-10 S/cm) in the alkyl-substituted complexes. Because the Pt−Pt interactions in the [Pt(NH2R)4][PtCl4] compounds are presumably weak, these substances may be regarded as self-assembled supramolecular structures. Nonetheless, the prepared complexes show some characteristics of rigid-rod polymers with flexible side chains; for example, they are insoluble when the alkyl chains are short but become soluble for longer alkyl chains, and they are able to form two-dimensional hexagonal or sheet structures. The complexes melt under decomposition above 100 °C. The soluble [Pt(NH2R)4][PtCl4] complexes form gels with fibrillar structures at temperature ranges that depend on the length of R. Films and fibers with uniaxially oriented fibrils were prepared from gels by drawing and electrostatic spinning. The mixed-metal complexes [Pd(NH2R)4][PtCl4] and [Pt(NH2R)4][PdCl4] (R = octyl) were also synthesized. The chemical and physical properties of the compounds with palladium differed significantly from those of [Pt(NH2R)4][PtCl4]. In particular, one of these complexes is insoluble, whereas the other one decomposes relatively quickly in solution.

Published
1999

35. Toward a Force Spectroscopy of Polymer Surfaces

Author

Feldman, K., Tervoort, T., Smith, P., and Spencer, N. D.

Abstract

The adhesional forces between a series of polymer film surfaces and chemically well-defined atomic force microscopy tips have been measured and found to depend strongly on the chemical nature of both probe and sample surfaces. For a given series of polymers, the ranking in adhesion strength was markedly different for polar and nonpolar probes, irrespective of the precise chemical composition of those probes. In the case of nonpolar polymers, a correlation of adhesion force with calculations based on the Lifshitz theory of Van der Waals interactions was found. In the case of polar polymers, a reasonable correlation with water-contact angle was observed. The adhesional differences between different probe tips translate into reversals of chemical contrast in high-spatial-resolution lateral force images, when examining polymer blends using chemically different tips, demonstrating the potential of this approach for the nanometer-scale, friction-mediated surface-chemical imaging of polymers. Central to these experiments has been the use of perfluorodecalin as a medium for measuring interactions. Employment of this liquid greatly facilitates measurement of the forces between the probe tip and the polymer surface.

Published
1998

36. Continuum damage mechanics: combining thermodynamics with a thoughtful characterization of the microstructure

Author

Hütter, M., Tervoort, T., Hütter, M., and Tervoort, T.

Abstract

We formulate a macroscopic description of the mechanics of damaged materials. To represent the microstructure, the distribution of crack sizes is captured by way of the Minkowski functionals, or so-called quermass integrals, while a second-rank tensor is used to describe the average orientation of the cracks. A two phase-type approach is adopted to distinguish elastically strained material from unstrained regions in the wake of the cracks. Using nonequilibrium thermodynamic techniques, the driving force for the growth of the microcracks is naturally identified. In particular, Griffith's law is generalized to assemblies of polydisperse crack sizes. Due to the detailed characterization of the microstructure, we are also able to account for the plastic zones at the rims of the cracks that are known to hamper the crack growth, and to discuss possible forms of the damage parameter. The presented approach separates in a transparent fashion the incorporation of fundamental thermodynamic and mechanic principles on one hand, from the specification of the material and details of the crack formation and growth on the other hand

37. A simple method for the determination of refractive indices of (rough) transparent solids

Author

Nussbaumer, R., Halter, M., Tervoort, T., Caseri, W., Smith, P., Nussbaumer, R., Halter, M., Tervoort, T., Caseri, W., and Smith, P.

Abstract

Simple methods for the determination of refractive indices of transparent polymers and inorganic and organic solids of irregular geometry or with scratched or corrugated surfaces are rare. A classical procedure is based on the invisibility of a body immersed in a liquid with the same refractive index as that of the body. In order to avoid the laborious procedure connected with the search for a liquid with matching refractive index and to find an approach which is independent of the observation by eye, we describe here a modified immersion method which allows the ready determination of the refractive index of solids. The present method is based on the interpolation of the maximum transmission (nTmax) of a solid immersed in liquids with different, typically non-matching, refractive indices. Illustrations with quartz glass, crown glass and poly(vinylidene fluoride) (PVDF) films showed that nTmax can be determined with a reproducibility of ± 0.003. By comparison with refractive indices determined by ellipsometry, it was concluded that the refractive index of a solid can be determined with the modified immersion method within an accuracy better than ± 0.01 when systematic errors resulting from the fit method are also taken into consideration

39. Determination of the molecular weight distribution of ultrahigh molecular weight polyethylene from solution rheology

Author

Vincenzo Ianniello, Salvatore Costanzo, Rossana Pasquino, Giovanni Ianniruberto, Enrico Troisi, Theo A. Tervoort, Nino Grizzuti, Ianniello, V., Costanzo, S., Pasquino, R., Ianniruberto, G., Troisi, E., Tervoort, T. A., and Grizzuti, N.

Subjects
Mechanics of Materials, Mechanical Engineering, General Materials Science, Condensed Matter Physics
Abstract

We investigate the linear rheology of ultrahigh molecular weight polyethylene (UHMWPE) solutions with the aim of determining the molecular weight distribution of the polymer. The UHMWPE is dissolved in oligo-ethylene in order to avoid issues related to unfavorable interactions with the solvent. To prepare the solutions, UHMWPE, solvent, and a fixed amount of antioxidants are mixed by means of a corotating twin-screw microcompounder. All prepared solutions are within the concentrated regime, as confirmed by the scaling laws of the main rheological parameters (plateau modulus, relaxation time, and zero-shear viscosity) with concentration. Based on the viscoelastic response of the solutions, we adopt a heuristic approach to extrapolate the linear viscoelastic behavior of the melt, according to a time-concentration superposition principle. Such a technique allows us to span many decades of angular frequency, eventually attaining the terminal relaxation regime. The latter is difficult to achieve by direct measurements in the molten state because of experimental issues such as extremely long experimental times and thermal limits. The viscoelastic spectrum of the melt is used to obtain the molecular weight distribution (MWD) according to the time-dependent diffusion/double reptation model. The MWD of UHMWPE evaluated by using this approach agrees well with data obtained from gel permeation chromatography.

Published
2022

40. Structuring Hydrogel Cross-Link Density Using Hierarchical Filament 3D Printing.

Author

Bayles AV, Pleij T, Hofmann M, Hauf F, Tervoort T, and Vermant J

Abstract

Polymer hydrogels, water-laden 3D cross-linked networks, find broad application as advanced biomaterials and functional materials because of their biocompatibility, stimuli responsiveness, and affordability. The cross-linking density reports material properties such as elasticity, permeability, and swelling propensity. However, this critical design parameter can be challenging to template locally. Here, we report a continuous processing scheme that uses laminar flow to direct the organization of cross-linking density across a single sample. Dilute and concentrated poly(ethylene glycol) diacrylate solutions are fed into custom serpentine millifluidic devices. These feature a modular sequence of splitting, rotation, and recombination elements, which create patterned streamlines that serve as a template for hierarchical concentration distributions. Poly(acrylic acid) microgels impart viscoplasticity, which stabilizes layered flow during multiplication and ensures reliable advection. The devices produce structured, seamless filaments, which are then arranged into objects using 3D printing, and photopolymerized to secure the heterogeneous distribution. The flow-encoded, multiscale architecture provides mechanical contrast, which is demonstratively exploited to program robust and reversible shape transformations, potentially useful in soft actuator and sensor applications. The unique structures achieved, and the geometrically dictated, chemistry-agnostic operating principles used to achieve them, provides a new means to engineer hydrogels to suit a variety of applications.

Published
2022
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41. Ultrasound-mediated piezoelectric differentiation of neuron-like PC12 cells on PVDF membranes.

Author

Hoop M, Chen XZ, Ferrari A, Mushtaq F, Ghazaryan G, Tervoort T, Poulikakos D, Nelson B, and Pané S

Subjects
Animals, Cell Culture Techniques, Neurons metabolism, PC12 Cells, Rats, Signal Transduction, Cell Differentiation radiation effects, Electric Stimulation, High-Energy Shock Waves, Neurons cytology, Neurons radiation effects, Ultrasonic Waves
Abstract

Electrical and/or electromechanical stimulation has been shown to play a significant role in regenerating various functionalities in soft tissues, such as tendons, muscles, and nerves. In this work, we investigate the piezoelectric polymer polyvinylidene fluoride (PVDF) as a potential substrate for wireless neuronal differentiation. Piezoelectric PVDF enables generation of electrical charges on its surface upon acoustic stimulation, inducing neuritogenesis of PC12 cells. We demonstrate that the effect of pure piezoelectric stimulation on neurite generation in PC12 cells is comparable to the ones induced by neuronal growth factor (NGF). In inhibitor experiments, our results indicate that dynamic stimulation of PVDF by ultrasonic (US) waves activates calcium channels, thus inducing the generation of neurites via a cyclic adenosine monophosphate (cAMP)-dependent pathway. This mechanism is independent from the well-studied NGF induced mitogen-activated protein kinases/extracellular signal-regulated kinases (MAPK/ERK) pathway. The use of US, in combination with piezoelectric polymers, is advantageous since focused power transmission can occur deep into biological tissues, which holds great promise for the development of non-invasive neuroregenerative devices.

Published
2017
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42. Collagen nerve conduits releasing the neurotrophic factors GDNF and NGF.

Author

Madduri S, Feldman K, Tervoort T, Papaloïzos M, and Gander B

Subjects
Animals, Chick Embryo, Ganglia, Spinal growth & development, Glial Cell Line-Derived Neurotrophic Factor metabolism, Materials Testing, Nerve Growth Factor metabolism, Stress, Mechanical, Collagen chemistry, Delayed-Action Preparations chemistry, Glial Cell Line-Derived Neurotrophic Factor administration & dosage, Nerve Growth Factor administration & dosage
Abstract

Artificial nerve conduits (NC) can clinically be instrumental for facilitating the surgery of damaged peripheral nerves. To improve axonal regeneration of injured peripheral nerves, we have developed collagen nerve conduits (NC) releasing glial cell line-derived neurotrophic factor (GDNF) alone or in combination with nerve growth factor (NGF), which exert synergistic action on axonal growth. Degradation of the NC and their mechanical and drug release properties were controlled by two means: (i) cross-linking the collagen tubes by physical means, through a dehydro-thermal treatment (DHT), before loading with the neurotrophic factors (NTFs) GDNF or GDNF/NGF; and (ii) coating the drug-loaded collagen tubes with layers of poly(lactide-co-glycolide) (PLGA). Non-cross-linked collagen NC (C-NC) released high amounts of NTFs during the initial 2-3 days of incubation, whereas the DHT-treated collagen NC (C(dht)-NC) did not show a prominent burst effect. The release kinetics was similar for GDNF alone and GDNF co-delivered with NGF. Within 30 days, the C-NC released 78% and 83% of the total doses of GDNF and NGF, respectively, whereas the C(dht)-NC released only 68% of GDNF and 56% of NGF. The bioactivity of the NTFs released up to 30 days was confirmed by an in vitro bioassay using chicken embryonic dorsal root ganglion (DRG) explants. The C(dht)-NC also possessed adequate mechanical resistance against radial compression, the pull-out of a suture thread, and loss of patency upon bending. Modulus and pull-out strength increased in the order of C-NC, C(dht)-NC approximately Neuragen, and Neurolac, with the latter two products being commercially available collagen and polyester NC, respectively. In vitro degradation time upon incubation with collagenase increased in the same order for the collagen-based NC. In conclusion, co-delivery of synergistically acting GDNF and NGF from structurally improved NC may be a promising tool for the successful repair of peripheral nerve defects., (Copyright 2009 Elsevier B.V. All rights reserved.)

Published
2010
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