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Friday, 19 July 2013

Femtoscale surface chemistry arrays by Microfluidic Pen Lithography

Reporting in Nature Communications, team from ICN2, UAB, Diamond Light Source and NanoInk report lithographic method for creating femtolitre surface chemistry arrays

A team led by researchers from ICN2's NANOup Group has pioneered a new lithographic method for creating arrays of femtoscale chemical reactions or crystallisations by controlled dispensing and mixing of femtolitre reagent volumes. They describe their new method, Microfluidic Pen Lithography (MPL), in the latest issue of Nature Communications, in an article entitled "Femtolitre chemistry assisted by microfluidic pen lithography". The team comprised ICN2 Group Leader and ICREA Research Professor Daniel Maspoch, and Laboratory Engineer Carlos Carbonell, of the NANOup Group, and colleagues at the Universitat Autonoma de Barcelona (UAB), Diamond Light Source (Didcot, UK) and NanoInk (Skokie, USA).

There is ever-growing demand for performing experiments at femtolitre or even smaller scale, from chemical synthesis to biological studies or high-throughput screening. This in turn has sparked the development of methods for dispensing and controlling reagents at these miniscule volumes, to date performed either by using specially engineered microdevices and wells, or by encapsulating reagents in vesicles such as micelles. However, the former tends to be rather costly, whereas the latter is very limited in terms of high-throughput. Thus, the ICN2 researchers and their colleagues sought a cheaper, simpler and more versatile method that would enable creation of arrays in a spatially ordered fashion, whether for combinatorial synthesis, process development (e.g. testing of crystallisation conditions), or chemical or biological screening.

Professor Maspoch and co-workers turned to lithography—namely, to microfluidic pens. They devised a two-step process in which femtolitre droplets are first generated, and then femtolitre volumes are precisely delivered into these droplets. By performing sequential rounds of droplet generation and volume addition, they were able to rapidly mix reagents for in situ reactions.

As proof-of-concept, they performed a series of femtoscale tests on surfaces, studying the mixing parameters and capabilities; crystallisation of metal-organic frameworks (MOFs); acid-base reactions (between fluorescein acid and KOH); biological recognition reactions; and screening of new metal-peptide networks. The chemistry was done in water or organic solvents.

Whilst MPL is not the first method for performing femtoscale chemistry, it is the first method reported to date for creating femtoscale combinatorial arrays on surfaces. The team is confident that MPL will gradually mature, and expand in scope, as have other lithographic methods, such as Dip-Pen Nanolithography (DPN). One future milestone that they hope will enable dramatic advances for high-throughput chemical synthesis, and chemical or biological screening, is the creation of multi-tip pens for MPL (similar to those now available for DPN), which will make simultaneous dispensing of multiple reagents possible.

To read the article "Femtolitre chemistry assisted by microfluidic pen lithography", click here.