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Microsystems are commonly manufactured by photolithographic or injection moulding techniques in a variety of realizations and on almost any material. A perennial problem in the manufacturing of microsystems is the difficulty to obtain hybrid devices that incorporate distinct materials with different functionalities. In most of the cases, cumbersome prototyping and high investment needed for manufacturing are additional problems that add to the cost of the final product. Such drawbacks are true not only for lab-on-a-chip but also for certain microreactor applications. Most importantly, in many commercial applications where an intermediate product between full fluidics control and a 'strip' is needed, such restraints prohibit the feasibility of reduction to practice. Screen printing on the other hand is a low cost technique that has been used for years in mass producing two-dimensional low cost reproductions of a mask pattern for circuits and art incorporates prototyping in production and allows the use of an almost limitless variety of materials as 'inks'. In this work it is demonstrated that taking advantage of the deposited ink's three-dimensional nature, screen printing can be used as a versatile and low cost technique for the fabrication of microchannels. Microchannels with dimensions in the order of 100 μm were fabricated that could readily incorporate functionalities through the choice of the materials used to create the microstructure. Variables have been investigated through a factorial experimental design as important process parameters that affect the resolution and print thickness of the resulting microchannels that incorporate electroactive elements. Such studies can lead to the optimization of the process for custom applications.

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Lateral-flow immunosensing devices continue to be the most successful commercial realization of analytical microdevices. They owe their success to their simplicity, which significantly depends on the capillary-driven flow and versatile technological platform that lends itself to fast and low-cost product development. To compete with such a convenient product, microsystems can benefit from simple-to-operate fluid manipulation. We show that the capillary-driven flow in microchannels can be manipulated with electrochemically activated valves with no moving parts. These valves consist of screen-printed electrode pairs that are transversal to the flow. One of the electrodes is solvent-etched to produce a superhydrophobic surface that provides passive stopping and facilitates low-voltage (~1 V) actuation of the flow via electrowetting. The operation of such valves in the stop-go mode, with a response time between 2 and 45 sec depending on the type and concentration of salt, is demonstrated. Mechanistic investigations indicated that the response depends on at least three phenomena that contribute to electrocapillarity: the electrochemical double-layer capacitance, specific counterion adsorption, and possible electrohydrodynamic effects.