Vapor Phase Polymerization of EDOT from Submicrometer Scale Oxidant Patterned by Dip-Pen Nanolithography

Some of the most exciting recent advances in conducting polymer synthesis have centered around the method of vapor phase polymerization (VPP) of thin films. However, it is not known whether the VPP process can proceed using significantly reduced volumes of oxidant and therefore be implemented as part of nanolithography approach. Here, we present a strategy for submicrometer scale patterning of the conducting polymer poly­(3,4-ethylenedioxythiophene) (PEDOT) via in situ VPP. Attolitre (10^–18 L) volumes of oxidant “ink” are controllably deposited using dip-pen nanolithography (DPN). DPN patterning of the oxidant ink is facilitated by the incorporation of an amphiphilic block copolymer thickener, an additive that also assists with stabilization of the oxidant. When exposed to EDOT monomer in a VPP chamber, each deposited feature localizes the synthesis of conducting PEDOT structures of several micrometers down to 250 nm in width. PEDOT patterns are characterized by atomic force microscopy (AFM), conductive AFM, two probe electrical measurement, and micro-Raman spectroscopy, evidencing in situ vapor phase synthesis of conducting polymer at a scale (picogram) which is much smaller than that previously reported. Although the process of VPP on this scale was achieved, we highlight some of the challenges that need to be overcome to make this approach feasible in an applied setting

Organic Solvent-Based Graphene Oxide Liquid Crystals: A Facile Route toward the Next Generation of Self-Assembled Layer-by-Layer Multifunctional 3D Architectures

We introduce soft self-assembly of ultralarge liquid crystalline (LC) graphene oxide (GO) sheets in a wide range of organic solvents overcoming the practical limitations imposed on LC GO processing in water. This expands the number of known solvents which can support amphiphilic self-assembly to ethanol, acetone, tetrahydrofuran, <i>N</i>-dimethylformamide, <i>N</i>-cyclohexyl-2-pyrrolidone, and a number of other organic solvents, many of which were not known to afford solvophobic self-assembly prior to this report. The LC behavior of the as-prepared GO sheets in organic solvents has enabled us to disperse and organize substantial amounts of aggregate-free single-walled carbon nanotubes (SWNTs, up to 10 wt %) without compromise in LC properties. The as-prepared LC GO-SWNT dispersions were employed to achieve self-assembled layer-by-layer multifunctional 3D hybrid architectures comprising SWNTs and GO with unrivalled superior mechanical properties (Young’s modulus in excess of 50 GPa and tensile strength of more than 500 MPa)

List of studies using IPFP as the stem cell source and the growth factors used.

<p>List of studies using IPFP as the stem cell source and the growth factors used.</p

Histology of week 4 chitosan-ASC constructs in chondrogenic and control media.

<p>There is a paucity of cellular attachment and growth in control media and lack of toluidine blue staining. Chitosan fibres are clearly stained by eosin. The cells that have grown and attached to the chitosan structure under chondrogenic media shows extracellular matrix deposition with strong toluidine blue staining, suggesting the presence of proteoglycans. Magnification 20×. A–D represent whole tissue images with scale bars at 500 µm as indicated. E–F represents magnified images with scale bars at 20 µm as indicated.</p

Immunohistochemistry of week 4 pellet culture in control and chondrogenic media.

<p>Collagen type II and proteoglycan is expressed in chondrogenic pellet compared with no expression in control media. Collagen type I is expressed in both control and chondrogenic pellet. Magnification 20×. Scale bars at 50 µm as indicated.</p

Photoswitchable Layer-by-Layer Coatings Based on Photochromic Polynorbornenes Bearing Spiropyran Side Groups

Herein, we present the synthesis of linear photochromic norbornene polymers bearing spiropyran side groups (poly­(SP-R)) and their assembly into layer-by-layer (LbL) films on glass substrates when converted to poly­(MC-R) under UV irradiation. The LbL films were composed of bilayers of poly­(allylamine hydrochloride) (PAH) and poly­(MC-R), forming (PAH/poly­(MC-R))_<i>n</i> coatings. The merocyanine (MC) form presents a significant absorption band in the visible spectral region, which allowed tracking of the LbL deposition process by UV–vis spectroscopy, which showed a linear increase of the characteristic MC absorbance band with increasing number of bilayers. The thickness and morphology of the (PAH/poly­(MC-R))_<i>n</i> films were characterized by ellipsometry and scanning electron microscopy, respectively, with a height of ∼27.5 nm for the first bilayer and an overall height of ∼165 nm for the (PAH/poly­(MC-R))₅ multilayer film. Prolonged white light irradiation (22 h) resulted in a gradual decrease of the MC band by 90.4 ± 2.9% relative to the baseline, indicating the potential application of these films as coatings for photocontrolled delivery systems

Relative chondrogenic gene expression between control and chondrogenic pellets and cell-scaffold constructs at 4 weeks.

<p>Collagen type II gene was not expressed in all control cultures for both pellets and cell-scaffolds at week 4. Both collagen type II and aggrecan genes were significantly increased by week 4 over control groups (*p<0.05; t-test). The increase in SOX9 was less significant between the control groups and the chondrogenic groups at 4 weeks. These results represent 3 separate experiments using 3 separate biological replicates (N = 3) as well as triplicate internal replicates for each qPCR reaction. Mean plotted with error bars representing the SEM.</p

In vitro culture of cell-scaffold constructs using cell inserts.

<p>Scaffolds were cut using a 6×10⁵ ASCs in a 24 tissue culture plate well inserts with an internal diameter of 6.5 mm and permeable membrane of 3.0 µm pore size.</p

3D printed chitosan scaffold.

<p>(A) Macroscopic image of a 3D printed chitosan scaffold showing strands of chitosan extruded in a 3D lattice pattern overlying each other forming a 3D structure. (B) Scanning electron microscope (SEM) image showing the lattice network of chitosan fibres. Scale bars as indicated.</p

Macroscopic image of pellet cultures in control and chondrogenic media at 4 weeks.

<p>A comparative image showing pellets cultured in control vs chondrogenic media shows a distinct difference in size at 4 weeks between the larger chondrogenic pellets and the smaller control pellet.</p