| 1. |
- Duineveld, P.C., et al.
(författare)
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Diffusion of solvent in PDMS elastomer for micromolding in capillaries
- 2002
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 18:24, s. 9554-9559
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Tidskriftsartikel (refereegranskat)abstract
- Micromolding in capillaries is a soft lithography method for patterning materials. We have studied the diffusion of solvent from the excavated microsized channels in the stamp into the PDMS material, both theoretically and experimentally. It was demonstrated that a model of 1-D diffusion of solvent through a PDMS stamp, coupled with a mass conservation of the solvent in the channels, leads to a quantitatively accurate model for the velocity of the boundary between liquid-filled and vapor-filled microchannels in the stamp. With the model the diffusion coefficient of the solvent into PDMS was successfully determined.
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| 2. |
- Immerstrand, Charlotte, et al.
(författare)
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Conjugated-polymer micro- and milliactuators for biological applications
- 2002
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Ingår i: MRS bulletin. - : Springer Science and Business Media LLC. - 0883-7694 .- 1938-1425. ; 27:6, s. 461-464
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Tidskriftsartikel (refereegranskat)abstract
- The development of new conjugated-polymer tools for the study of the biological realm, and for use in a clinical setting, is reviewed in this article. Conjugated-polymer actuators, based on the changes of volume of the active conjugated polymer during redox transformation, can be used in electrolytes employed in cell-culture media and in biological fluids such as blood, plasma, and urine. Actuators ranging in size from 10 μm to 100 μm suitable for building structures to manipulate single cells are produced with photolithographic techniques. Larger actuators may be used for the manipulation of blood vessels and biological tissue.
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| 3. |
- Jager, Edwin W.H., et al.
(författare)
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The cell clinic : closable microvials for single cell studies
- 2002
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Ingår i: Biomedical microdevices (Print). - 1387-2176 .- 1572-8781. ; 4:3, s. 177-187
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Tidskriftsartikel (refereegranskat)abstract
- We present the development of a cell clinic. This is a micromachined cavity, or microvial, that can be closed with a lid. The lid is activated by two polypyrrole/Au microactuators. Inside the microvials two Au electrodes have been placed in order to perform impedance studies on single or a small number of cells. We report on impedance measurements on Xenopus leavis melanophores. We could measure a change in the impedance upon cell spreading and identify intracellular events such as the aggregation of pigment granules. The electrical data is correlated to optical microscopy.
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| 4. |
- Johansson, DM, et al.
(författare)
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Synthesis of soluble phenyl-substituted poly(p-phenylenevinylenes) with a low content of structural defects
- 2002
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Ingår i: Macromolecules. - : American Chemical Society (ACS). - 0024-9297 .- 1520-5835. ; 35:13, s. 4997-5003
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Tidskriftsartikel (refereegranskat)abstract
- The synthesis and characterization of two new soluble poly(p-phenylenevinylenes) (PPVs) are reported. The polymers are poly(2-2',5'-bis(octyloxy)benzene)-1,4-phenylenevinylene) (BOP-PPV) and poly(2-(2',5'-bis(octyloxy)benzene)-5-methoxy-1,4-phenylenevinylene) (BOPM-PPV). Both polymers have been polymerized at high and low temperatures to study the formation of structural defects. It is shown that both methoxy groups as side chains and low polymerization temperatures decrease the content of defects in the final polymer. As a consequence, the polymers with lower concentration of defects exhibit higher electroluminescence yields in light-emitting diodes. In addition to this, the polymers with a low content of defects exhibited longer operational lifetimes in these devices. The highest photoluminescence quantum yield in the solid state and electroluminescence efficiency were found to be 72% and 1.74%, respectively.
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| 5. |
- Johansson, Tomas, et al.
(författare)
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Conductivity of de-doped poly(3,4-ethylenedioxythiophene)
- 2002
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Ingår i: Synthetic metals. - 0379-6779 .- 1879-3290. ; 129:3, s. 269-274
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Tidskriftsartikel (refereegranskat)abstract
- The conductivity of chemically and electrochemically de-doped poly(3,4-ethylenedioxythiophene) (PEDOT) has been investigated in situ. We observe a decrease in the conductivity by 4-5 orders of magnitude. The change of conductivity is correlated to the change of electronic structure. We obtain the dielectric function of the polymer by spectroscopic ellipsometry and note that anisotropy is observed in both doped and neutral states. © 2002 Elsevier Science B.V. All rights reserved.
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| 6. |
- Jonforsen, M., et al.
(författare)
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Synthesis and characterization of poly(quinoxaline vinylene)s and poly(pyridopyrazine vinylene)s with phenyl substituted side-groups
- 2002
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Ingår i: Synthetic metals. - 0379-6779 .- 1879-3290. ; 131:1-3, s. 53-59
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Tidskriftsartikel (refereegranskat)abstract
- Poly(quinoxaline vinylene) and poly(pyridopyrazine vinylene) with 3(2'-ethylhexyloxy)phenyl side-groups have been synthesized and compared with similar polymers with purely aliphatic side-chains. The new polymers had smaller bandgaps, and from cyclic voltammetry it was seen that the phenyl substituted side-groups made the polymers easier to reduce, with half wave potentials of -1.02 and -1.33 V versus Ag/AgCl for the poly(pyridopyrazine vinylene) and poly(quinoxaline vinylene) respectively. The attachment of the phenyl substituted side-groups had counteracting effects on the stability towards photo-oxidation, which resulted in improved stability of the poly(pyridopyrazine vinylene) compared to its equivalent with purely aliphatic side-chains, while the poly(quinoxaline vinylene) showed decreased stability. © 2002 Elsevier Science B.V. All rights reserved.
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| 7. |
- Jonforsen, M, et al.
(författare)
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Synthesis and characterization of soluble and n-dopable poly(quinoxaline vinylene)s and poly(pyridopyrazine vinylene)s with relatively small band gap
- 2002
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Ingår i: Macromolecules. - : American Chemical Society (ACS). - 0024-9297 .- 1520-5835. ; 35:5, s. 1638-1643
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Tidskriftsartikel (refereegranskat)abstract
- Synthesis and characterization of poly(quinoxaline vinylene)s and poly(pyridopyrazine vinylene)s with linear and branched aliphatic side chains are reported. The electron affinity of the polymers was measured with cyclic voltammetry (CV) and found to be highest for the pyridopyrazine vinylene polymers, Compared to CN-MEH-PPV, the pyridopyrazine vinylene polymers were easier to reduce, while the quinoxaline derivatives were harder. UV-vis absorption measurements showed that the polymers have relatively small band gaps.
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| 8. |
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| 9. |
- Nilsson, Peter, et al.
(författare)
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Conformational transitions of a free amino-acid-functionalized polythiophene induced by different buffer systems
- 2002
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Ingår i: Journal of Physics. - : IOP Publishing. - 0953-8984 .- 1361-648X. ; 14:42, s. 10011-10020
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Tidskriftsartikel (refereegranskat)abstract
- A chiral, 3-substituted polythiophene with an amino-acid function shows pH-dependent visible, emission and circular dichroism spectra in buffered aqueous solution. At pH equal to the pI of the amino-acid, the backbone adopts a nonplanar right-handed helical conformation and the polymer chains are separated from each other. Increasing pH leads to a more planar conformation of the backbone and an aggregation of the polymer chains occurs. A lower pH will also lead to a more planar conformation of the backbone, but aggregation of the polymer chains appears to be absent. The aggregates are disrupted by increasing ionic strength in alkaline buffer systems, indicating hydrogen bonding is important for aggregation. On the other hand, ions containing an amino group and one or more hydroxyl groups induce a more planar conformation of the polymer backbone.
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| 10. |
- Nyberg, Tobias, et al.
(författare)
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Macromolecular nanoelectronics
- 2002
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Ingår i: Current applied physics. - 1567-1739 .- 1878-1675. ; 2:1, s. 27-31
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Tidskriftsartikel (refereegranskat)abstract
- We have explored new organic materials and fabrication methods to fabricate organic photodiodes and light emitting diodes. Grafting of a fullerene derivative to a polythiophene backbone yielded an integrated acceptor-donor polymer that we used as the active material in organic photodiodes. Using a method of soft lithography. soft embossing, we fabricated submicron structures to be used as organic light emitting diodes. Employing a silicone rubber replica (stamp) of an optical diffraction grating we transferred the grating pattern to an organic resist layer by placing the stamp in conformal contact with the resist. The transferred pattern was subsequently used as an etch mask for the processing of the device. The structures were successfully utilized as light emitting diodes and photodiodes, with device characteristics influenced by the imposed structure. (C) 2002 Published by Elsevier Science B.V.
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