Microfluidics and electrochemistry: an emerging tandem for next-generation analytical microsystems

Microfluidic and electrochemical technologies have been at the forefront of the development of emerging analytical microsystems. Microfluidics and electrochemistry show a synergistic relationship, empowering their inherent features. Thus, integration of microfluidics and electrochemical (bio)sensors is envisioned as a powerful tandem for boosting the next generation of lab-on-a-chip platforms, including point-of-care and point-of-need systems. In this review, a general overview of the advantages, drawbacks, and gaps as well as remaining challenges and future trends of coupling microfluidics and electrochemical cells is presented. Special attention is given to the manufacturing and scale-up of the integrated devices and all those aspects that can push on the development of true lab-on-a-chip platforms for reaching the industrial domain and actual commercialization.     

Smart portable electrophoresis instrument based on multipurpose microfluidic chips with electrochemical detection

A second generation of a battery-powered portable electrophoresis instrument for the use of ME with electrochemical detection was developed. As the first-generation, the main unit of the instrument (150 mm × 165 mm × 95 mm) consists of four-outputs high-voltage power supply (HVPS) with maximum voltage of 3 KV and acquisition system (bipotentiostat) containing 2-channels for dual electrochemical detection. A new reusable microfluidic platform was designed in order to incorporate the microchips with the portable instrument. In this case, the platform is integrated to the main unit of the instrument so that it is not necessary to have any external cable for the interconnection of both parts, making the use of the complete system easier. The new platform contains all the electrical connections for the HVPS and bipotentiostat, as well as fluidic ports for driving the solutions. The microfluidic electrophoresis instrument is controlled by means of a user-friendly interface from a computer. The possibility of wireless connection (Bluetooth?) allows the use of the instrument without any external cable improving the portability. Therefore, the second generation brings a more compact and integrated electrophoresis instrument for "in situ" applications using microfluidic chips in an easy way. The performance of the electrophoresis system was initially evaluated using single- and dual-channel SU-8/Pyrex microchips with different models of integrated electrodes including microelectrodes and interdigitated arrays. The method was tested in different analytical applications such as separation of neurotransmitters, chlorophenols, purine derivatives, vitamins, polyphenolic acids, and flavones.     

Fabrication and evaluation of single- and dual-channel (Pi-design) microchip electrophoresis with electrochemical detection

A new dual-channel microchip capillary electrophoresis (MCE) has been developed on glass substrates for the first time with electrochemical detection. Dual-channel (called Pi-design) as well as single-channel microchips have been fabricated on soda-lime glass using photolithography, wet etching and thermal bonding. Moreover, a laser writing system has been applied for the fabrication of photomasks with the different microchip designs (single- and dual-channel configurations). The microfabricated channels have been characterized by optical, confocal and scanning electron microscopy. The resulting single- and dual-channel microchips have been evaluated using an end-channel amperometric detector based on one (single-channel) or two (dual-channel) 100-mum gold wires aligned at the outlet of the separation channel. Parameters affecting the separation of several phenolic compounds (dopamine, p-aminophenol and hydroquinone) have been studied in the glass microchips. Thus, the influence of separation voltage, detection potential and background electrolyte has been examined in the single-channel microchip. Different total length microchannel has been compared. Furthermore, the possibility of carrying out two simultaneous measurements has been demonstrated in the new dual-channel microchip electrophoresis. The injection format has been checked and resulted to be critical, in such a way that a special and new form is employed for obtaining simultaneous signals at both channels. Analytical characteristics, such as sensitivity and reproducibility have been evaluated and resulted very adequate.