Actuation principle

The core components of a complete microsystem are the integrated sensing, acting or passive micromechanical devices. In most cases, a naked chip manufactured in bulk or surface micromachining is used for the detection of a physical or chemical quantity or some actuation principle, like the dosage of ink droplets in inkjet printheads. A complete microsystem can consist of a complex set of these devices. 

The classification of micropumps is somewhat arbitrary. One might distinguish micropumps according to the type of momentum transfer to the solution (mechanical or electrical), but for practical reasons, we choose here to distinguish them by the presence or absence of mechanical valves, this being a generic element of many pumps. A second classification can be made using the actuation principles (see Fig. 5). Various examples of the different pump-types are listed below. 

Unit-dose and bi-dose systems are designed to deliver one or two doses into the nostril(s) (Fig. 9). As compared to multidose pump systems, unit-dose and bi-dose systems are distinguished by a different actuation principle. The dose volume is predetermined by the prefilled glass vial and sealed with a rubber stopper. The glass and rubber are the identical materials used in syringes. The benefit is an optimal protection against environmental influences. Unif-dose and bidose systems can be sterilized, and an aseptic filling procedure justifies the omission of preservatives. 

The actuation principles for the devices listed in the above is so clear that the explanation is not necessary. The metals or the alloys, which are appropriate to the listed devices, are classified into three categories ... 

Here, the microfluidic actuation principles that are utiziled in massively parallel analysis are outlined briefly. This is followed by some commercial application examples. Due to the similar principle, microarrays and picowell plates are presented together, followed by bead based assays. 

It is obvious that certain actuating properties of transducer materials are far beyond the ones of conventional actuating principles. This enables to use them in special application areas such as lightweight construction, active vibration control, or the development of highly dynamic systems for instance. 

Shen et al. [2] exploit the peristaltic actuation principle in an active-valve magnetic micropump with advantages as high efficiency and selfpriming. The magnetic active-valve micropump consists of three in series chambers in middle layer which the central actuation chamber of this layer acts as a pumping chamber, while the left and right chambers act as valves. 

The rapid development of new methods of fabrication and microfluidic components enables the desired control and manipulation of small amounts of fluids. The microvalves in microelec-tromechanical systems (MEMS) are essential elements of a micro total analysis system. Typically, there are two types of microvalve one is the passive valve, the operation of which is dependent upon its surrounding pressure conditions, and the other is the active valve, which can be controlled actively. Active valves are categorized in three major ways initial working state, control pattern, and actuation principle. Each microvalve has advantages and disadvantages from the... 

The actuation principle of IPMCs is based on the electromechanically induced bending. At the same time, in nature, biological muscles utilize... 

Actuators Current MEMS Actuator Principles Materials Selection Conjugated Polymer Microactuators 14-17... 

When heated up, the austenitic structure will be established again. At the same time the SM element will return to its original shape because neither the phase transformation nor the de-twinning of the martensitic structure involves changes to the atomic lattice. The SM element may exert high forces when recovering its predefined shape therefore the SM effect can be employed as a new actuator principle. 

The properties of electrically activated shape memory actuators described so far have indicated that these actuators are well-suited to drive mechanical mechanisms. The advantages and disadvantages of this kind of new actuator principle are smnmarized in Table 6.6. 

Shape memory actuators offer a lot of advantages, but there are also some quite serious drawbacks. When comparing SM actuators with other actuator principles (such as piezoelectric stacks or solenoids), it should be taken into consideration that research for improved shape memory materials is relatively young. With shape memory alloys and actuators slowly gaining commercial importance it is expected that in the next few years new SM alloys will emerge that have higher transition temperatures and good effect stability [85,86]. 

Micro assembly. While most of the technology used to fabricate parts of millimeter or micrometer size could be copied and modified from microelectronic fabrication processes, this is not true for micro assembly. There are scarcely any devices suitable for a small- or medium-scale automated assembly of micromechanical systems. Micro assembly opens a broad field of potential applications for new actuator principles. An example is the handling of millimeter-sized, lightweight parts under clean-room conditions and with small operational space available. 

For some applications the simultaneous incorporation of two actuation principles in a hybrid way can be of interest. An example for this is the combined use of electromagnetic and electrostatic forces in a microvalve [311]. The electromagnetic force is applied for generating large displacements in opening or closing the valve, whereas the electrostatic force can keep the valve in its closed position with very little power consumption. Similarly, the... 

Figure 6.140 shows the measurement results obtained with the two selfsensing actuator principles for electrical large-signal operation. They display the characteristics of the three transfer paths of the bidirectional actuator, illustrated in the form of s-Sd, Sr S and Fr F trajectories. In this case, the values X, and ym in the (6.80), (6.77) and (6.78) correspond to the inverse control voltage, the measured control voltage and the measured piezoelectric charge. 

Compared to the mid 1990s, there has not been too much variation in the sensing and actuation principles to be used. With regard to sensing optical fibre and piezoelectric sensors are dominant, followed by MEMS, which however still rather plays a secondary role. On the actuation side piezoelectric... 

The electrolysis of water an actuation principle for mems with a big opportunity. Mechatronics 10 571-581... 

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