FULL INTEGRATION AND AUTOMATION OF IMMUNOASSAY PROTOCOLS BY ROTATIONALLY ACTUATED DISSOLVABLE FILM VALVES Charles Nwankire 1* , Robert Gorkin 2 , Jonathan Siegrist 1 , Jennifer Gaughran 2 , Di-sien Chan 1 and Jens Ducrée 1,2 1 Biomedical Diagnostics Institute, National Centre for Sensor Research, 2 School of Physical Sciences, Dublin City University, Ireland ABSTRACT Here we describe a fully integrated and automated, multi-step immunoassay protocol utilizing our water-dissolvable films (DFs) actuated, centrifugo-pneumatic valving scheme [1]. This technique establishes a sequence of laboratory unit op- erations comprising of blood separation, metering, mixing/incubation, and liquid reagent release from on-board reservoirs for washing and detection by mere control of the rotational frequency. During storage at rest and at low rotational frequen- cies, the sacrificial DF valves provide permanent liquid and vapor barriers. However, beyond a critical burst frequency rang- ing up to 3500 rotations per minute (rpm), these valves yield by inverting a metastable gas-liquid layer to trigger the wetting and thus dissolution of the DFs. KEYWORDS: Centrifugal, Microfluidics, Dissolvable film, valving, Integration, Sacrificial valve, Burst frequency, Vapor barrier INTRODUCTION Interest in sacrificial valves is due to their ability to create vapor barriers and to precisely gate liquid flows at high rota- tional frequencies which traditional passive valves (e.g. hydrophobic patches) would not be able to sustain. Due to the vapor barriers created by these sacrificial valves, they can be used for on-board reagent storage. While some sacrificial valves such as wax and optofluidic valves have previously been reported, they require external actuators such as laser diodes in order to be activated [2, 3]. The use of DFs as sacrificial valves goes well beyond the state-of-the-art, eliminating the need for exter- nal actuators other than the spindle motor intrinsic to centrifugal platforms. We here consider for the first time the advantageous use of DF-based valving on a centrifugal microfluidic platform [4, 5]. In DF-based centrifugo-pneumatic valving, a gas pocket is pressurized by the centrifugal field acting on the confining liquid plug (see Fig. 1). Beyond a critical spinning frequency, the inverted liquid-gas stack destabilizes and the liquid wets the film, thus dissolving the sacrificial membrane. A novel, multi-material fabrication method was developed for facilitating the system assembly [1]. Figure 1: Frame sequence and schematic representation of the trapped air ballast holding back the liquid. When burst frequency is reached, gas/liquid inversion occurs; liquid enters the pneumatic chamber and dissolves the DF, thus opening the valve. RESULTS AND DISCUSSION Multi – Step Immunoassay (IA) protocol - Figure 2 provides an illustration of a proposed design for a fully integrated and automated multi-step assay protocol, involving blood separation, metering and mixing. In this design, liquid reagents are pre-loaded in the blood separation, wash and mixing chambers respectively. 978-0-9798064-4-5/μTAS 2011/$20©11CBMS-0001 1665 15th International Conference on Miniaturized Systems for Chemistry and Life Sciences October 2-6, 2011, Seattle, Washington, USA