Surface printing: Stamp of approval
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Surface printing: Stamp of approval
NPG Asia Materials research highlight | doi:10.1038/asiamat.2010.150
Published online 13 September 2010
A molecule-selective microcontact printing technique could provide an alternative approach for molecular detection.
Fig. 1: Photograph of a PDMS stamp for molecule-selective microcontact printing.
A technique for transferring positively charged molecules onto a flake of gold has been developed by a team of researchers in China and Belgium[1].
The method could be used to develop sensors that recognize specific compounds such as biological molecules, which could aid disease diagnosis.
The technique is a form of microcontact printing, where a stamp is used to pick up an ‘ink’ — in this case, positively charged molecules — and print them onto a surface.
The researchers, led by Huaping Xu of Tsinghua University in Beijing, China, made the stamp using a process that imprints a layer-by-layer film on its surface. The scientists coated a plastic called PDMS with layers of a diazo resin and a mixture of porphyrin and poly(acrylic acid). Exposing the structure to ultraviolet light caused the diazo resin and poly(acrylic acid) to form a chemical bond. The porphyrin could then be washed away with solvent to leave recesses on the surface of the stamp (Fig. 1).
The team found that these recesses could pick up molecules of Alcian Blue 8GX, a positively charged dye molecule that is commonly used for staining cells to reveal the presence of certain sugar molecules. The stamp did not pick up a negatively charged version of the dye, proving that it selectively bound only positively charged molecules.
The stamp loaded with Alcian Blue ink was then pressed onto a gold substrate. After a processing step, the researchers observed that the Alcian Blue had been transferred to the gold surface. “The film can also act as an ink reservoir to achieve multiple printing,” says Xu.
Each Alcian Blue molecule bears four positive charges. To prove the versatility of their method, the team also showed that microcontact printing could be achieved with molecules of glutathione, which bears a single positive charge.
These proof-of-principle experiments show that the method could be used to transfer a wide variety of molecules in a similar way, including the commonly used fluorescent dye Rhodamine 6G, or even large biological molecules. The team is now extending the technique to create surfaces that can distinguish between enantiomers — two mirror-image forms of a molecule — or between molecules of slightly different size.
Reference
1. Liu, Z.H.,1,2,3 Yi, Y.,1 Xu, H.P.,1* Zhang, X.,1 Ngo, T.H.4 & Smet, M.4 Cation-selective microcontact printing based on surface-molecular-imprinted layer-by-layer films. Adv. Mater. 22, 2689 (2010). | article
Author affiliation
1. Key Lab of Organic Optoelectronics and Molecular Engineering, Department of Chemistry, Tsinghua University, Beijing 100084, China
2. Key Laboratory of Photochemical Conversion and Optoelectronic Materials, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, China
3. Graduate University of the Chinese Academy of Sciences, Beijing 100049, China
4. Molecular Design and Synthesis, Catholic University of Leuven, Celestijnenlaan 200F, B-3001 Leuven, Belgium
*Email:
[email protected]
This research highlight has been approved by the author of the original article and all empirical data contained within has been provided by said author."
