Wendell K. Tomazelli Coltro 1 José A. Fracassi da Silva 2, 3 Heron D. Torres da Silva 3 Eduardo M. Richter 3 Rogério Furlan 4 Lúcio Angnes 3 Claudimir L. do Lago 3 Luiz H. Mazo 1 Emanuel Carrilho 1 1 Instituto de Química de São Carlos, Universidade de São Paulo, São Carlos-SP, Brazil 2 Instituto de Química, Universidade Estadual de Campinas, Campinas-SP, Brazil 3 Instituto de Química, Universidade de São Paulo, São Paulo-SP, Brazil 4 Department of Physics and Electronics, University of Puerto Rico at Humacao, Humancao, Puerto Rico Electrophoresis microchip fabricated by a direct-printing process with end-channel amperometric detection We describe the development of an electrophoresis microchip fabricated by a direct- printing process, based on lamination of printed polyester films with end-channel amperometric detection. The channel structures are defined by polyester (base and cover) and by a toner layer (walls). The polyester-toner devices presented an electro- osmotic flow (EOF) magnitude of ,10 25 cm 2 V 21 s 21 , which is generated by a polymeric mixture of the toner and polyester composition. The microelectrodes used for detec- tion were produced combining this laser-printer technology to compact discs. The performance of this device was evaluated by amperometric detection of iodide and ascorbate. The detection limits found were 500 nmol ? L 21 (135 amol) and 1.8 mmol ? L 21 (486 amol) for iodide and ascorbate, respectively. Keywords: Amperometric detection / Microchip / Miniaturization DOI 10.1002/elps.200406091 1 Introduction Since the introduction of the micrototal analysis system (mTAS) concept [1], also called lab-on-a-chip, the poten- tial of microfabrication has been explored and it is still in the focus of research in order to bring new technologies to analytical systems. Microfluidic devices have been applied in almost every area of separation science [2, 3], particularly in miniaturized capillary electrophoresis (CE) systems. Advantages of working in a microchip electro- phoresis format are numerous and include fast analysis times, the use of high field strengths, minute consumption of reagents, and the possibility for disposable/portable devices. Numerous articles have been published in the last years, which show a dramatic advance in fabrication methods, operating techniques, and applications in var- ious research fields [2–6]. Microanalytical devices were initially constructed using silicon, quartz, and glass substrates [2, 3]. The popularity of these materials comes from the ease of design and fabrication of both prototypes and small series of micro- fluidic chips, using standard methods of microelectronics, such as patterning and etching [7]. Microsystems utilizing these substrates have demonstrated successfully their analytical capability. Yet, the fabrication processes are time-consuming, and the resulting microchips are usually expensive for use as disposable devices on a cost-effec- tive basis [8]. Polymer materials, in contrast, offer attrac- tive mechanical and chemical properties, low cost, ease of fabrication, biocompatibility, and higher flexibility. These advantages make polymeric materials very attrac- tive for generating truly integrated disposable devices for in-the-field and point-of-care applications [9–11]. Several works on polymer-based microfluidic devices have appeared in literature [12]. Polymers used include poly(- methyl methacrylate) (PMMA), polyvinylchloride (PVC), polycarbonate (PC), polystyrene (PS), polyurethane (PU), and poly(dimethylsiloxane) (PDMS). Techniques used for making polymer microfluidic device include laser abla- tion, hot embossing, injection molding, silicone rubber casting, and replica molding [7, 12]. The search for new materials and new technologies has been a permanent objective of analytical community. Lago and co-workers [13] described recently a new Correspondence: Prof. Dr. Emanuel Carrilho, Instituto de Quí- mica de São Carlos, Universidade de São Paulo, Avenida Trabal- hador São Carlense, 400 Cx. Postal 780, 13560-970, São Carlos- SP, Brazil E-mail: emanuel@iqsc.usp.br Fax: +55-16-3373-9983 Abbreviations: CTAH, cethyltrimethylammonium hydroxide; DTL, double toner layer; EC, electrochemical; PDMS, poly(di- methylsiloxane); PMMA, poly(methyl methacrylate); STL, single toner layer 3832 Electrophoresis 2004, 25, 3832–3839  2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim