Abstract
A new analytical detector based on a liquid drop resistor–capacitor (RC) filter is described, in which transformed gain vs. frequency curves are used to analyze compounds. This detector can be used to detect either charged or neutral species (that are dielectrically different) which are dissolved in a liquid (e.g., water, alcohol, solvent mixtures, etc.). This device was fabricated by modifying an electrowetting on dielectric (EWOD)-based experimental setup. When a liquid drop is placed on a dielectric surface, the system acts as a RC filter. At a given frequency, gain is a function of conductivity, surface tension, dielectric constant, double-layer thickness of the solid–liquid drop interface, as well as the applied voltage. Since different liquids and solutions have different physical properties, each liquid/solution has a unique curve (peak) in gain vs. frequency plot. This is the basic principle behind the detector. Different amounts of zinc chloride dissolved in water, benzalkonium chloride in water, 1-methylimidazole in water, cetyltrimethyl-ammonium chloride (CTAC) in water, and CTAC dissolved in ethylene glycol solutions were tested with the detector as proof of principle. The device can be used as a stand-alone detector or can easily be coupled with droplet based microfluidic lab-on-a-chip systems such as EWOD-based microfluidic chips.
Similar content being viewed by others
References
Nanayakkara YS, Moon H, Armstrong DW (2010) ACS Appl Mater Interfaces 2:1785–1787
Nanayakkara YS, Perera S, Bindiganavale S, Wanigasekara E, Moon H, Armstrong DW (2010) Anal Chem 82:3146–3154
Cordella C (2010) Actual Chim 345:13–18
Kumar A, Pluntke M, Cross B, Baret J-C, Mugele F (2005) Finite conductivity effects and apparent contact angle saturation in AC electrowetting. In: Proceedings of the Materials Research Society Fall Meeting, Boston, USA, Nov 2005
Jones TB, Wang K, Yao D (2004) Langmuir 20:2813–2818
Jones TB (2002) Langmuir 18:4437–4443
Zeng J, Korsmeyer T (2004) Lab Chip 4:265–277
Chatterjee D, Shepherd H, Garrell RL (2009) Lab Chip 9:1219–1229
BENZALKONIUM CHLORIDE || Skin Deep Cosmetics Database | Environmental Working Group (2011). Available from www.ewg.org Accessed 8/5/2011
Prince SJ, McLaury H, Allen LV, McLaury P (1999) J Pharm Biomed Anal 19:877–882
United States Pharmacopeia 23/National Formulary 18 (1995) US Pharmacopeial Convention, Inc., Maryland, pp. 2218–2219
CETRIMONIUM CHLORIDE || Skin Deep Cosmetics Database | Environmental Working Group (2011). Available from www.ewg.org Accessed 8/5/2011
Terol A, Gomez-Mingot M, Maestre SE, Prats S, Todoli JL, Paredes E (2010) Int J Cosmet Sci 32:65–72
Anderson DJ (1989) Clin Chem 35:2152–2153
Schreiner C, Zugmann S, Hartl R, Gores HJ (2010) J Chem Eng Data 55:1784–1788
Cheung KC, Di Berardino M, Schade-Kampmann G, Hebeisen M, Pierzchalski A, Bocsi J, Mittag A, Tárnok A (2010) Cytometry Part A 77A:648–666
Agilent Technologies (2006) Agilent impedance measurement handbook: a guide to measurement technology and techniques. Agilent Technologies, Santa Clara
Ren H, Fair RB, Pollack MG (2004) Sens Actuators B B98:319–327
Gong J, Kim C (2008) Lab Chip 8:898–906
Shih SCC, Fobel R, Kumar P, Wheeler AR (2011) Lab Chip 11:535–540
Mugele F, Baret J (2005) J Phys Condens Matter 17:R705–R774
Wijethunga PAL, Nanayakkara YS, Kunchala P, Armstrong DW, Moon H (2011) Anal Chem 83:1658–1664, Washington, DC, USA
Widegren JA, Saurer EM, Marsh KN, Magee JW (2005) J Chem Thermodyn 37:569–575
Nanayakkara YS, Moon H, Payagala T, Wijeratne AB, Crank JA, Sharma PS, Armstrong DW (2008) Anal Chem 80:7690–7698
Millefiorini S, Tkaczyk AH, Sedev R, Efthimiadis J, Ralston J (2006) J Am Chem Soc 128:3098–3101
Moon H, Cho SK, Garrell RL, Kim CJ (2002) J Appl Phys 92:4080
Acknowledgments
The authors thank Prof. Hyejin Moon for allowing the authors to use her laboratory and Robert A. Welch Foundation (Y0026) for funding.
Author information
Authors and Affiliations
Corresponding author
Electronic supplementary material
Below is the link to the electronic supplementary material.
ESM 1
(PDF 535 kb)
Rights and permissions
About this article
Cite this article
Nanayakkara, Y.S., Armstrong, D.W. A liquid drop RC filter apparatus for detection. Anal Bioanal Chem 401, 2669–2678 (2011). https://doi.org/10.1007/s00216-011-5426-0
Received:
Revised:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s00216-011-5426-0