Towards integrated microliquid handling systems

Abstract

In this paper we describe components for integrated microliquid handling systems such as fluid injection analysis, and first results of planar integration of components. The components discussed are channels, passive and active valves, actuators for micropumps, micromixers, microflow sensors, optical detectors, pumps and dosage systems. The dosage system described comprises a flow sensor and a pump micromachined on a single silicon wafer sandwiched between Pyrex wafers. The liquid pump is of the reciprocating type with a thermo-pneumatic actuator. The microliquid flow sensor is based on the thermal anemometer type. Both pump and flow sensor are realized in a 3 inch (100)-Si wafer using a KOH bulk etch from both sides of the wafer. The dosing system allows accurate dosing of liquid in the wl regime and can easily be integrated with components as mixers and detectors to microliquid handling systems. A new concept for micromixing of liquids is introduced and its feasibility is demonstrated. The mixer allows fast mixing of small amounts of two liquids and it is applicable to microliquid handling systems. The,mixer has a channel for the liquid, an inlet port for t h e reagent, and a mixing area, the bottom of which has 400 micronozzles (15 p m x i 5 Nm). Through these nozzles, a reagent is injected into the sample liquid, making many microplumes. These plumes speed up mixing by diffusion over a short distance.

Some Important Problems and Progress in Micro / Nano-scale Thermal Science and Engineering

“…All this is closely related with the practical application, for example, due to the rapid development of low-temperature technology and thin metal film and metal wire application growth needs, Tien et al [ 10] on the thin metal film and metal lines were calculated and found that its conductivity and thermal conductivity are lower than the corresponding value in the macroscopic case, one of the reasons is close to the surface of the average free electrons due to the interface of the scattering will be shortened, and the electron mean free path increases with the decrease of temperature, especially at low temperature, when the average free path of energy carrier (such as electron) is the smallest of the given sample In the order of magnitude, the transport of these carriers will reflect the dependence on the size of the sample [11], resulting in the traditional theory of the predicted physical properties of the sample and its real value there is a significant deviation, it is these theories and experiments the observed contradictions contribute to the development of micro-scale thermal science. Micro-scale heat transfer and fluid science cover a very broad field [12][13][14][15][16][17][18][19][20], such as solid-liquid films, semiconductor devices, optical devices, superconducting devices, chip cooling devices, micro-electromechanical systems, biochips, microsensors, laser processing, thermal medical engineering, life and thermal science and contains a lot of challenging topics.…”

Micro Total Analysis Systems: Microfluidic Aspects, Integration Concept and Applications

“…[2] into a (mostly) electrical signal. However, recently miniature components such as mixers, filters, separation columns, reactors etc., have been developed [3,4] that are capable of pretreating the sample, carrying out a chemical reaction or separating the different components within a sample mixture. The possibility to integrate such components into one miniaturized system leads to a more generalized view on information gathering (see Fig.…”

“…Several review articles describing miniaturized devices for fluid handling have been published that give excellent and detailed overviews of the state of the art [3,4]. Here, some examples of microfabricated valves and pumps will be given to illustrate the possibilities of silicon microtechnology.…”

An electrochemical active valve

“…For microfluidics, basic components like pumps and valves, activated by different principles [2], have already been realized with the use of silicon microtechnology (Table 1; for an extensive comparison of active valves see [3,41) Depending on the application, some actuation principles may be preferable, but most of these need either high voltages (eg, electrostatic, piezoelectric) or have quite high power consumption with low efficiency (eg, heat dissipation in the case of thermal actuation), which limits their applicability. The goal of this research is to develop a micromachined active valve that provides a continuous regulation around a desired pressure value.…”