Fluidic-mechanical actuators

This section presents indicative implementations of actuator microconveyor platforms or actuators that could potentially be used for planar micromanipulation, separated into categories according to the classification made in the introduction thermomechanical, electrostatic, electromechanical and fluidic-mechanical. For each implementation, a brief description of the actuators, their operation principle as well as their reported performance characteristics is given unfortunately not all the information relevant within the scope of this chapter has been reported by the respective authors. At the end of the section, a comparison between the most promising actuators or platforms for planar micromanipulation is made in a concentrative table and the most suitable of them are determined based on the criteria proposed in the previous paragraph. 

Fig. 13 Integrated PDMS microfluidic system comprising four modules an injection/separation module in which pumping was entirely supported by electroosmotics a protein trapping module a circular micromixer where pumping was mechanically achieved and an enzyme reaction module. Fluidic channels are in red, actuation channels are in blue-green. Valve actuation channels were filled with water in order to avoid air entering the fluidic channels through the PDMS membranes. Integrated valves are numbered from 1 to 6. Reproduced from [135]...

Gray BL, Collins SD, Smith RL (2004) Interlocking mechanical and fluidic interconnections for microfluidic circuit boards. Sens Actuators A 112 18-24... 

Microfluidic Control Sequential and combinatorial delivery of signals to cells or tissue in microfluidic devices can be accomplished by using built-in control systems. Several microfluidic tools including valves, pumps, mixers, fluidic oscillators, fluidic diodes, etc. have been developed to accomplish fluidic control in these devices. These components can either be passive or active. Examples of passive elements include one-way valves (flap, ball) and hydrophobic patohes which take advantage of the interactiOTi between the chemical surface properties of the substrate and Uquid. Active elements, on the other hand, typically require some type of actuation mechanism. Several mechanisms for force transduction in microfluidic devices include mechanical, thermal, electrical, magnetic, and chemical actuation systems as well as the use of biological transducers. There has been a significant amount of work in this area that has been presented in a review by Erickson and Li [5]. 

Compared to conventional LoaC devices, the LoaD platform displays several intrinsic advantages regarding the integration of optical detection methods. The actuation and the detector as well as all moving parts can be entirely delegated to a robust macroscopic unit which resembles a conventional ODD, e.g., a CD or a DVD player. The LoaD device thus constitutes a fluidically and optically merely passive module. Also, the mechanical interface between the polymer disc and the optical detection module is usually made up by a simple, central clamp holder. Finally, the optical detection can be performed by conventional optical equipment with the disc either at rest or rotating a suitable frequency to match the acquisition rate capability of the detector. 

While microelectronics can be described as the fabrication of electrical components like transistors, diodes, resistors and capacitors on a semiconductor substrate, mostly silicon, MEMS and MOEMS are using the manufacturing technologies of microelectronics to fabricate mechanical and optical structures as well as sensing or actuating devices. Typical examples are pressure sensors, microphones, acceleration and angular-rate sensors, magnetic compasses, inkjet heads, micro-scanners, micro-fluidic devices, biosensors, etc., to name some. 

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