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Concept

Polyimide

Résumé

vignette|Mousse isolante Solimide Les polyimides (en abrégé PI) sont des polymères colorés (souvent ambrés) qui comportent des groupes imide dans leur chaîne principale. Les polyimides sont surtout connus pour leur thermostabilité. Classification Selon la composition de leur chaine squelettique, les polyimides peuvent être classés en :

aliphatiques ;
semi-aromatiques ;
aromatiques : c'est le cas des polyimides les plus largement utilisés en raison de leur caractère thermostable.

Selon les réactifs utilisés pour leur synthèse, les polyimides peuvent être : Ces polymères de spécialité se trouvent sur le plan commercial sous les noms de Kapton (commercialisé en 1962) et Vespel de DuPont, Upilex d'UBE, P84 d'Evonik Fibers, Meldin de Saint-Gobain Performance Plastics, etc. Polyimides linéaires Plusieurs voies de synthèse sont possibles pour préparer les polyimides linéaires. Parmi ces méthodes :

la réaction entre un dianhydride et une diamine (la plus coura

Source officielle

https://fr.wikipedia.org/wiki/Polyimide

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Publications associées (47)

Surface Microstructures on Planar Substrates and Textile Fibers Guide Neurite Outgrowth: A Scaffold Solution to Push Limits of Critical Nerve Defect Regeneration?

Thomas Lehnert, Li Yao

The treatment of critical size peripheral nerve defects represents one of the most serious problems in neurosurgery. If the gap size exceeds a certain limit, healing can't be achieved. Connection mismatching may further reduce the clinical success. The present study investigates how far specific surface structures support neurite outgrowth and by that may represent one possibility to push distance limits that can be bridged. For this purpose, growth cone displacement of fluorescent embryonic chicken spinal cord neurons was monitored using time-lapse video. In a first series of experiments, parallel patterns of polyimide ridges of different geometry were created on planar silicon oxide surfaces. These channel-like structures were evaluated with and without amorphous hydrogenated carbon (a-C:H) coating. In a next step, structured and unstructured textile fibers were investigated. All planar surface materials (polyimide, silicon oxide and a-C:H) proved to be biocompatible, i.e. had no adverse effect on nerve cultures and supported neurite outgrowth. Mean growth cone migration velocity measured on 5 minute base was marginally affected by surface structuring. However, surface structure variability, i.e. ridge height, width and inter-ridge spacing, significantly enhanced the resulting net velocity by guiding the growth cone movement. Ridge height and inter-ridge distance affected the frequency of neurites crossing over ridges. Of the evaluated dimensions ridge height, width, and inter-ridge distance of respectively 3, 10, and 10 mu m maximally supported net axon growth. Comparable artificial grooves, fabricated onto the surface of PET fibers by using an excimer laser, showed similar positive effects. Our data may help to further optimize surface characteristics of artificial nerve conduits and bioelectronic interfaces.

Public Library Science2012

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Design and printing of a coplanar capacitive proximity sensor to detect the gap between dielectric foils edges

Danick Briand, Rubaiyet Iftekharul Haque, Martin Lubej

This paper presents the design and development of a coplanar capacitive proximity sensor for the detection of the gap between the edges of dielectric foils. The finite element analysis is applied to study the design of the sensor by investigating the effects of different physical parameters, like, the sensing electrodes width, the spacing between them and the thickness of the substrate on its responses. The sensitivity of the sensor increases with the ascending electrode width; but is negatively affected by the growing spacing between electrodes. Conversely, the foil edge gap detection range rises with the growing electrode width and spacing between electrodes. Moreover, the optimum sensor performance is observed for the foil edge gap positioned centered with the sensing electrodes and the target foil remaining in contact with its surface. The capacitive proximity sensor with optimum set of parameters is fabricated on a polyimide foil by the inkjet of the sensing electrodes. The sensor demonstrates an average optimum sensitivity of 0.105 fF/μm for an edge gap detection range of 500 µm with a 450 µm thick polyethylene foil, when the vertical gap between the foil and the active area of the sensor is maintained to zero. The sensitivity and the detection range capability reduce significantly with the increasing vertical gap between the sensor and foil.

2022

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We have experimentally studied the variation in electrical resistance of flexible platinum lines patterned on polyimide foil when they are subjected to circular bending constraints. The lines were patterned by means of standard photolithography and sputtering deposition. Two different photolithography masks were used for comparative evaluation: an un-expensive transparency mask and a standard chromium mask. Measurements of the temperature coefficient of resistance (TCR) and time stability of the resistance have been acquired for lines bent down to 1.25 mm radius of curvature on a customized bending setup, showing good reliability results. The robustness of the lines has been also assessed by registering their change in resistance while bending at different radii of curvature. The lines showed reliability issues for radii of curvature below 1.25 mm, presenting a resistance variation of 19% for transparency mask-fabricated lines and 9% for chromium mask-fabricated lines. The worse reliability performances of transparency mask lines, compared to the chromium mask ones, was found to be due to their imperfect edges, which promoted the formation and propagation of cracks during bending. The results of the experiments in this work permitted to compare the performances of flexible conductive lines with, different geometry and fabricated with two different masks, establishing quantitative and qualitative bending limits for their appropriate operation in flexible electronics systems. (C) 2014 Elsevier Ltd. All rights reserved.

Elsevier2014

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Surface Microstructures on Planar Substrates and Textile Fibers Guide Neurite Outgrowth: A Scaffold Solution to Push Limits of Critical Nerve Defect Regeneration?

Thomas Lehnert, Li Yao

Public Library Science2012