Flexible polyimides

Figure 12.12 Image of an organo-metallic palladium precursor solution that was deposited by the author on a flexible polyimide substrate via spin coating and thermally processed at 200 °C for 30 seconds.

Before implantation several in vitro tests were performed. For evaluation of a possible toxic reaction, we investigated the material and the whole devices in vitro with cell culture methods. Direct contact and extraction tests with a mouse fibroblasts cell line (L 929) and a neuroblastoma cell line (neuro-2-a) were performed according to the international standard ISO 10993 ( Biological Evaluation of Medical Devices ). The materials and devices showed no toxicity, i.e. no significant differences in membrane integrity of the cell membranes, mitochondrial activity and DNA synthesis rate. The neuro-2-a cell line is so sensitive that even small changes in process technology are detectable. The flexible polyimide structures proved to be non toxic. 

Fig. 2. Photograph of a flexible polyimide-based in vivo sensor for glucose, lactate and pH measurements...

A similar concept based on a mixture of BMI-MDA (Matrimide 5292 A) and bis-alkenylphenol (Matrimide 5292 B) with a flexible polyimide has been patented as a heat-resistant adhesive [117]. 

The semi-IPN concept has also been used in order to improve the high-temperature adhesive properties of a flexible polyimide. Polyimide prepared with isophthaloyldiphthalic anhydride and mefa-phenylenediamine presents good adhesive properties but is limited to 270 °C. By blending it with a bisnadimide... 

Highly reflective, surface-metallized, flexible polyimide films containing silver are accessible by the incorporation of [Ag(hfac)] into poly(amic acid) solutions followed by thermal curing to 300 "C . The silvered films are thermally stable and maintain mechanical properties similar to those of the parent polyamide. 

Covers lightweight, flexible polyimide foam as a layered thermal-insulation-barrier material developed for use within a specific frequency range on submarines. Cunently there is only one Type, with three Gasses, 1, 2, and 3, with single, double and triple layers, respectively. The layers of polyimide foam are bonded to a polyj osphazene/barium sulfate sheet. 

Solimide Foam. [Ethyl] Flexible polyimide foam for thermal and acoustical insulation applies. 

Chip is attached face down and wire bonded to the interposer. A thin elastomer, sandwiched between the chip and interposer, cushions the chip and the solder-ball interconnects, relieving stresses (see Fig. 1.13). The interposer generally consists of a metallized, flexible polyimide tape on which are formed electrical connections by photolithographic processes. As a final step, the exposed wire bonds and edges of the chip are molded with epoxy. 

K. C. Cheung, P. Renaud, H. Tanila, and K. Djupsund. Flexible polyimide microelectrode array for in vivo recordings and current source density analysis. Biosens. Bioelectron., 22(8) 1783-1790, March 2007. 

S. Metz, B. A. D. Bertrand, and P. Renaud, Flexible polyimide probes with microelectrodes and embedded microfluidic channels for simultaneous drug delivery and multi-channel monitoring of bioelectric activity. Biosensors and Bioelectronics, 19(10), 1309-1318, 2004. 

For aerospace applications, several advanced sealants have been mentioned cyanosilicones (123),fluoroalkyl-arylenesiloxanylene (FASIL) (124), phosphonitrilic fluo-roelastomers (PNF ) (125,126), flexible polyimide (127), tetrafluoroethylene oxide phenylquinoxaline elastomer (FEX) (128), perfluoroalkyl ethers (129), etc. These advanced sealants have been used for fuel tank sealing, channel sealing, filleting, aerodynamic smoothing, and other assemblies. Basically, they should be high-temperature serviceable, fault-tolerant, and adhere well to metals and/or composites. 

The reaction product between BFBSI and BMJEP gave a flexible polyimide sealant with the following properties ... 

D.J. Liaw, EC. Chang, Highly organo-soluble and flexible polyimides with color lightness andtransparencybasedon2,2-te[4-(2-trifluoromethyl-4-aminophenoxy)-3,5-di-methylphenyljpropane, J. Polym. Sci., Part A Polym. Chem. 42 (22) (2004) 5766-5774. 

The integrated circuits were composed of a central power management system (CPMS) and a low power system (LPS), deployed on a flexible polyimide substrate on a ground plane, glued on the back side of the SIW. More details of the implementation are described in Ref. [27]. 

Synthsis and Characterization Two series of PBTA/PI block copolymers have been prepared from two different flexible polyimides. The chemical structures are illustrated in Scheme 1. 

Fig. 9.28. Flexible, polyimide based sieve electrodes interfacing regenerating axons in peripheral nerves...

Stieghtz, T. Koch, K.P. Schiittler, M Flexible, Polyimide-Based Modular Implantable Biomedical Microsystems for Neural Prostheses. IEEE Eng. in Med. and Biology Magazine, vol. 24, no. 5 (2005), pp. 58-65... 

The preparation of polyimides with magnetic filler content as humidity sensor devices represents a new research area. Because aromatic polyimides are more frequently utilized in sensing technology due to their excellent mechanical and thermal properties or radiation resistance (Sroog 1991) as well as their favorable thermal stability and dielectric properties (Hu et al. 2009), the development of new, more flexible polyimides requires different strategies. In order to increase the solubility of polyimides, two structural modifications of the polymer chain were proposed ... 

Multimodal tactile sensor on flexible polyimide substrate capable of sensing the hardness, roughness, temperature and thermal conductivity of the object in contact has been developed. The sensor is constructed using a polyimide substrate (Figure 8) and consists of multiple sensor nodes arranged in an array format[45]. 

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