Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is the most successful transparent conductive polymer widely used in functional organic devices. However, its potential in fabrication of highly conductive electrodes still has not been fully explored. This paper is an attempt to fill the existing gap of knowledge on possible post-treatments of dimethyl sulfoxide (DMSO)-doped PEDOT:PSS thin films. In the present study, surface morphology, optical and electrical properties of untreated and sulfuric acid treated DMSO-doped PEDOT:PSS multilayers on the glass coverslip substrates are examined. It is demonstrated that short-time sulfuric acid treatment enhances electrical and optical properties, and smoothens surface of the transparent conductive films. Enhancement of electrical conductivity by more than 30 % can be associated with increase in doping level, removal of excess PSS and accompanied shape alterations of the conjugated PEDOT chains. Acid treatment also results in smoother transmittance spectra and a slight improvement of optical transparency. Hence, sulfuric acid post-treatment can be considered as a simple and inexpensive technique for the complementary doping of DMSO-doped PEDOT:PSS films with the aim to develop the more effective transparent electrodes.

A photopolymerizable thiol-ene composition was prepared as a mixture of pentaerythritol tetrakis(3-mercaptopropionate) (PETMP) and 1,3,5-triallyl-1,3,5-triazine-2,4,6(1H,3H,5H)-trione (TTT), with 1 wt. % of 2,2-dimethoxy-2-phenylacetophenone (DMPA) photoinitiator. A systematic analytical analysis that investigated the crosslinked PETMP-TTT polymer coatings employed Fourier transform infrared spectroscopy, ultraviolet–visible spectroscopy, differential scanning calorimetry, thermogravimetric analysis, pencil hardness, thermo-mechanical cyclic tensile, scratch testing, and atomic force microscopy. These coatings exhibited high optical transparency and shape-memory that assisted scratch-healing properties. Scratches produced on the PETMP-TTT polymer coatings with different constant loadings (1.2 N, 1.5 N, and 2.7 N) were completely healed after the external stimulus was applied. The strain recovery ratio and total strain recovery ratio for PETMP-TTT polymer were found to be better than 94 ± 1% and 97 ± 1%, respectively. The crosslinked PETMP-TTT polymer network was also capable of initiating scratch recovery at ambient temperature conditions.

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Engineering of sophisticated synthetic 3D scaffolds that allow controlling behaviour and location of the cells requires advanced micro/nano-fabrication techniques. Ultrafast laser micro-machining employing a 1030-nm wavelength Yb:KGW femtosecond laser and a micro-fabrication workstation for micro-machining of commercially available 12.7 and 25.4 μm thickness polyimide (PI) film was applied. Mechanical properties of the fabricated scaffolds, i.e. arrays of differently spaced holes, were examined via custom-built uniaxial micro-tensile testing and finite element method simulations. We demonstrate that experimental micro-tensile testing results could be numerically simulated and explained by two-material model, assuming that 2-6 μm width rings around the holes possessed up to five times higher Young's modulus and yield stress compared with the rest of the laser intacted PI film areas of 'dog-bone'-shaped specimens. That was attributed to material modification around the micro-machined holes in the vicinity of the position of the focused laser beam track during trepanning drilling. We demonstrate that virgin PI films provide a suitable environment for the mobility, proliferation and intercellular communication of human bone marrow mesenchymal stem cells, and discuss how cell behaviour varies on the micro-machined PI films with holes of different diameters (3.1, 8.4 and 16.7 μm) and hole spacing (30, 35, 40 and 45 μm). We conclude that the holes of 3.1 μm diameter were sufficient for metabolic and genetic communication through membranous tunneling tubes between cells residing on the opposite sides of PI film, but prevented the trans-migration of cells through the holes. Copyright © 2016 John Wiley & Sons, Ltd.

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