Microsystems are gaining more and more interest in several technological areas. The complete integration of different basic elements like pumps, valves and reaction chambers is possible by the use of microtechnologies. In the field of micro analysis systems a mixing procedure of different solutions is often required. A static micromixer built up in silicon has been developed. The design and fabrication procedures of the micromixer allow the integration of other microcomponents like pumps, valves or sensors. The micromixer consists of two structures silicon wafers. The structured surfaces are bonded together by using a low temperature silicon direct bonding process. The structure of the mixer consists of several identical mixing elements. The size of one element is about . Each element consists of two or more microchannels for different liquids to be mixed. The arrangements of the microchannels in the elements lead to a mixing of the liquids. We found a homogeneous mixing after about 5 mixing elements for mixable liquids. Not mixable liquids will be emulsified after about 16 - 20 mixing elements.
Microactuators are an essential component in microsystems or microdevices, and in applications that include artificial muscles, pumps, valves, or switchers. Liquid‐crystalline elastomers are a new class of actuator material in the field of microsystem technologies, which can be used in standard processes. This newly developed actuator provides new possibilities in microfluidics because of its dimensional changes activated by the increase in temperature.
Dynamic micropumps employing pyramid-trunc shaped diffusers as dynamic passive valves have been developed, built and tested. They are particularly characterized by a very simple fabrication technology and good high frequency performance. A prototype being 5*5*lmm3 in size reached with methanol a Lero load pump rate of more than 300plimin and a maximum pump pressure of about 7kPa at 5kHz working frequency. Dynamic micropumps can, therefore, compete with known solutions of similar or even bigger size. Thc dircction-dependent behaviour of silicon microdiffusers have been cxpcriinentally investigated; the results arc discussed. Based on the found characteristics, a static model for dynamic membrane pumps has bccn derived. The calculatcd parameters match quite well the real values of different tested micropumps. By the static model, pump layout adapted to the demanded application becomcs easier.
Photo‐crosslinkable side‐chain liquid‐crystalline polymers (LCPs) containing photoreactive benzophenone cores are synthesized in order to obtain their corresponding side‐chain liquid‐crystalline elastomers (LCEs). This strategic synthesis allows thin elastomeric films and their integration into microsystems for actuators and micromachines to be obtained. As an example of this principle, a gripper was developed. The position of its arms can be changed by applying voltages from 1.5 to 3.5 V at different rates. Small changes in the liquid‐crystalline elastomer film cause strains of up to 150% in the microdevice and the capacity to move up to 400 times its own mass due to the nematic‐to‐isotropic transformation.magnified image
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