On chip droplet characterization: a practical, high-sensitivity measurement of droplet impedance in digital microfluidics.

We demonstrate a new approach to impedance measurement on digital microfluidics chips for the purpose of simple, sensitive, and accurate volume and liquid composition measurement. Adding only a single series resistor to existing AC droplet actuation circuits, the platform is simple to implement and has negligible effect on actuation voltage. To accurately measure the complex voltage across the resistor (and hence current through the device and droplet), the designed system is based on software-implemented lock-in amplification detection of the voltage drop across the resistor which filters out noise, enabling high-resolution and low-limit signal recovery. We observe picoliter sensitivity with linear correlation of voltage to volume extending to the microliter volumes that can be handled by digital microfluidic devices. Due to the minimal hardware, the system is robust and measurements are highly repeatable. The detection technique provides both phase and magnitude information of the real-time current flowing through the droplet for a full impedance measurement. The sensitivity and resolution of this platform enables it to distinguish between various liquids which, as demonstrated in this paper, could potentially be extended to quantify solute concentrations, liquid mixtures, and presence of analytes.

[1]  Saman Sadeghi,et al.  Micro-chemical synthesis of molecular probes on an electronic microfluidic device , 2011, Proceedings of the National Academy of Sciences.

[2]  Aaron R Wheeler,et al.  A feedback control system for high-fidelity digital microfluidics. , 2011, Lab on a chip.

[3]  M. Tabrizian,et al.  Nanostructured digital microfluidics for enhanced surface plasmon resonance imaging. , 2011, Biosensors & bioelectronics.

[4]  R. Fair,et al.  Low Voltage Electrowetting-on-Dielectric Platform using Multi-Layer Insulators. , 2010, Sensors and actuators. B, Chemical.

[5]  Hong Wu,et al.  A microfluidic platform for systems pathology: multiparameter single-cell signaling measurements of clinical brain tumor specimens. , 2010, Cancer research.

[6]  T. G. Mitchell,et al.  Multiplexed real-time polymerase chain reaction on a digital microfluidic platform. , 2010, Analytical chemistry.

[7]  P. Sullivan,et al.  Using capacitance measurements in EWOD devices to identify fluid composition and control droplet mixing , 2010 .

[8]  R. Zengerle,et al.  Microfluidic lab-on-a-chip platforms: requirements, characteristics and applications. , 2010, Chemical Society reviews.

[9]  R. Garrell,et al.  Integration of protein processing steps on a droplet microfluidics platform for MALDI-MS analysis. , 2010, Analytical chemistry.

[10]  Vittorio Ferrari,et al.  A microfluidic capacitance sensor for fluid discrimination and characterization , 2011 .

[11]  A. Wheeler,et al.  A digital microfluidic approach to proteomic sample processing. , 2009, Analytical chemistry.

[12]  Bernhard Weigl,et al.  Towards non- and minimally instrumented, microfluidics-based diagnostic devices. , 2008, Lab on a chip.

[13]  Chang-Jin C J Kim,et al.  All-electronic droplet generation on-chip with real-time feedback control for EWOD digital microfluidics. , 2008, Lab on a chip.

[14]  Da-Jeng Yao,et al.  DNA ligation of ultramicro volume using an EWOD microfluidic system with coplanar electrodes , 2008 .

[15]  Richard B. Fair,et al.  Digital microfluidics: is a true lab-on-a-chip possible? , 2007 .

[16]  G. Whitesides.  The origins and the future of microfluidics , 2006, Nature.

[17]  Fei Su,et al.  Concurrent testing of digital microfluidics-based biochips , 2006, TODE.

[18]  R. Garrell,et al.  Droplet-based microfluidics with nonaqueous solvents and solutions. , 2006, Lab on a chip.

[19]  M. Thompson,et al.  Scanning Kelvin nanoprobe detection in materials science and biochemical analysis. , 2005, The Analyst.

[20]  S. Quake,et al.  Microfluidics: Fluid physics at the nanoliter scale , 2005 .

[21]  Angelo Geraci,et al.  Digital field programmable gate array-based lock-in amplifier for high-performance photon counting applications , 2005 .

[22]  K. Chakrabarty,et al.  Ensuring the operational health of droplet-based microelectrofluidic biosensor systems , 2005, IEEE Sensors Journal.

[23]  C. Kim,et al.  Digital microfluidics with in-line sample purification for proteomics analyses with MALDI-MS. , 2005, Analytical chemistry.

[24]  John L. Crassidis,et al.  Sensors and actuators , 2005, Conference on Electron Devices, 2005 Spanish.

[25]  Richard B. Fair,et al.  Automated on-chip droplet dispensing with volume control by electro-wetting actuation and capacitance metering , 2004 .

[26]  T. Jones,et al.  Frequency-dependent electromechanics of aqueous liquids: electrowetting and dielectrophoresis. , 2004, Langmuir : the ACS journal of surfaces and colloids.

[27]  Howard A. Stone,et al.  ENGINEERING FLOWS IN SMALL DEVICES , 2004 .

[28]  Peter R. C. Gascoyne,et al.  Dielectrophoresis-based sample handling in general-purpose programmable diagnostic instruments , 2004, Proceedings of the IEEE.

[29]  Jong Wook Hong,et al.  Integrated nanoliter systems , 2003, Nature Biotechnology.

[30]  Jeong‐Yeol Yoon,et al.  Preventing Biomolecular Adsorption in Electrowetting-Based Biofluidic Chips. , 2003, Analytical chemistry.

[31]  S. Cho,et al.  Low voltage electrowetting-on-dielectric , 2002 .

[32]  C. Kim,et al.  Electrowetting and electrowetting-on-dielectric for microscale liquid handling , 2002 .

[33]  T. Jones,et al.  Dielectrophoretic liquid actuation and nanodroplet formation , 2001 .

[34]  M. Williams,et al.  CRC Handbook of Chemistry and Physics, 76th edition , 1996 .

[35]  W. M. Haynes.  CRC Handbook of Chemistry and Physics , 1990 .

[36]  A. Gobbi,et al.  Physical‐Electrical Properties of Silicon Nitride Deposited by PECVD on III–V Semiconductors , 1990 .

[37]  T. S. West.  Analytical Chemistry , 1969, Nature.