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Issue 18, 2012
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Accurate dispensing of volatile reagents on demand for chemical reactions in EWOD chips

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Abstract

Digital microfluidic chips provide a new platform for manipulating chemicals for multi-step chemical synthesis or assays at the microscale. The organic solvents and reagents needed for these applications are often volatile, sensitive to contamination, and wetting, i.e. have contact angles of <90° even on the highly hydrophobic surfaces (e.g., Teflon® or Cytop®) typically used on digital microfluidic chips. Furthermore, often the applications dictate that the processes are performed in a gas environment, not allowing the use of a filler liquid (e.g., oil). These properties pose challenges for delivering controlled volumes of liquid to the chip. An automated, simple, accurate and reliable method of delivering reagents from sealed, off-chip reservoirs is presented here. This platform overcomes the issues of evaporative losses of volatile solvents, cross-contamination, and flooding of the chip by combining a syringe pump, a simple on-chip liquid detector and a robust interface design. The impedance-based liquid detection requires only minimal added hardware to provide a feedback signal to ensure accurate volumes of volatile solvents are introduced to the chip, independent of time delays between dispensing operations. On-demand dispensing of multiple droplets of acetonitrile, a frequently used but difficult to handle solvent due to its wetting properties and volatility, was demonstrated and used to synthesize the positron emission tomography (PET) probe [18F]FDG reliably.

Graphical abstract: Accurate dispensing of volatile reagents on demand for chemical reactions in EWOD chips

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Publication details

The article was received on 10 Mar 2012, accepted on 12 Jun 2012 and first published on 15 Jun 2012


Article type: Paper
DOI: 10.1039/C2LC40244K
Lab Chip, 2012,12, 3331-3340

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    Accurate dispensing of volatile reagents on demand for chemical reactions in EWOD chips

    H. Ding, S. Sadeghi, G. J. Shah, S. Chen, P. Y. Keng, C. “. Kim and R. M. van Dam, Lab Chip, 2012, 12, 3331
    DOI: 10.1039/C2LC40244K

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