Field of the Invention The present invention relates to a microelectro- mechanical device with integrated control of a flow of a fluid, said device having a first sheet and a cover. which is arranged on the first sheet and connected thereto, the first sheet having, in its surface engaging the cover, a flow duct system formed in the surface and intended for the fluid, and the device further having an inlet to the flow duct system, an outlet from the flow duct system and at least one microsensor, which is mounted in the flow duct system and arranged to react to the fluid.

Background Art In a known device of this type, the first sheet is made of silicon and the cover consists of a second sheet which is also made of silicon. Before these sheets are placed on each other and interconnected, the duct system is formed in at least one of the two opposing sheet sur- faces, which takes place by vacuum etching. Such an etch- ing process requires great capital investments, and the cost of manufacture of this known device in small and medium-size series is therefore high.

For the device in operation to work properly, it is in certain applications necessary for the fluid to be heated to a temperature which is in a predetermined temperature range. Since silicon is a material with good thermal insulating power, quick heating of the fluid can- not take place by heating the silicon sheets, but use is made of a separate heating apparatus which is connected in front of the known device and through which the fluid is first passed to be heated before it is supplied to the flow duct system of the device and through this is passed to the sensor. This is a complicated technique which in addition requires a separate heating apparatus.

Summary of the Invention The object of the present invention therefore is to provide a device which is relatively simple and inexpen- sive to manufacture and which makes it possible to quick- ly heat a fluid in the flow duct system of the device in a simple manner.

According to the invention, this object is achieved by a device, which is of the type stated by way of intro- duction and characterised in that the first sheet has a first layer of polymer material which engages the cover and in which the flow duct system is formed, and that an electrically conductive layer, which is quickly eatable so as to quickly heat the fluid in the flow duct system by heat conduction, is arranged in one of the first sheet and the cover.

Microcomponents, such as micropumps and microvalves, can be arranged in the flow duct system.

In a preferred embodiment, the electrically conduc- tive layer consists of a carbon fibre sheet.

The electrically conductive layer is suitably arranged in the first sheet, the layer of polymer mate- rial being formed on the electrically conductive layer.

The first sheet advantageously has a second layer of polymer material, which is formed on the electrical- ly conductive layer at the side thereof opposite to the first layer of polymer material.

The cover preferably consists of a second sheet, which has a third layer of polymer material engaging the first layer of polymer material of the first sheet and an electrically conductive layer, on which the third layer <BR> <BR> <BR> of"polymer material is formed. A second flow duct system' coacting with the flow duct system in the first layer of polymer material of the first sheet and supplementing said flow duct system can be formed in the layer of poly- mer material of the second sheet.

Brief Description of the Drawing The invention will now be described in more detail with reference to the accompanying drawing.

Fig. 1 shows a device according to the invention in section along line I-I in Fig. 2.

Fig. 2 is a top plan view of a lower sheet included in the device.

Description of a Preferred Embodiment The device shown in the drawing has a first sheet 1 and a second sheet 2, which are placed on each other and interconnected. The drawing illustrates the device in a horizontal position, and therefore the first sheet 1 and the second sheet 2 will here be referred to as lower and upper sheet, respectively.

The lower sheet 1 has an upper layer 3 of polymer material, a lower layer 4 of polymer material and an intermediate layer 5 of an electrically conductive mate- rial, for instance a metal foil or a carbon fibre sheet.

In a preferred embodiment, the lower sheet 1 has an intermediate layer 5 which consists of a carbon fibre sheet, on which an upper and a lower layer 3 and 4, respectively, of polymer material have been applied in molten state and then rapidly cooled for consolidation of the polymer material.

The upper sheet 2 is formed in essentially the same way as the lower sheet 1 and thus has an upper layer 6 of polymer material, a lower layer 7 of polyer material and an intermediate layer 8 of an electrically conductive material, which in the preferred embodiment also consists of a carbon fibre sheet.

The two sheets 1 and 2 have the same dimensions, and the upper sheet 2 is arranged on the lower sheet 1 so as to fully cover the same and is therefore also referred to as cover sheet or cover. The sheets 1 and 2 are glued together.

It should here be noted that the thickness of the various sheets 3-8 is shown to be disproportionately

great in relation to the surface of the sheets 1 and 2.

The length and width of the sheets 1 and 2 are usually in the order of a few centimetres, and their total thickness is usually about 1 mm.

In connection with the application of the upper layer 3 on the electrically conductive layer 5 during manufacture of the lower sheet 1, the upper layer 3 of the lower sheet 1 has been provided with a flow duct system 9 for a fluid. The flow duct system 9 consists of grooves which have been embossed in the upper surface of the layer 3 by means of an embossing tool. The device has an inlet 10 to the flow duct system 9 and an outlet 11 from the same. The inlet 10 extends from the underside of the lower sheet 1 through its lower layer 4 and inter- mediate layer 5 into the flow duct system 9 in the vici- nity of one lateral edge of the sheet 1, and the outlet 11 extends from the flow duct system 9 through the inter- mediate layer 5 and lower layer 4 of the lower sheet 1 from the underside of the sheet 1 in the vicinity of the opposite lateral edge. In use of the device, a fluid is supplied to the flow duct system 9 via the inlet 10, through the flow duct system 9 and out of the same through the outlet 11.

Various microcomponents can be arranged in the flow duct system 9. In the embodiment illustrated, a micropump 12 and a microvalve 13 are arranged in the upstream part of the flow duct system 9. The micropump 12 is arranged to pump the fluid at the desired flow rate. The micro- valve 13, which is mounted at a junction in the flow duct system 9, is arranged to distribute the flow of the fluid between two branches 9a and 9b in the flow duct system 9 which extend from the junction. The microcomponents 12 and 13 are of prior-art type and controlled by means of a control unit 14 of prior-art type, which is mounted on the underside of the lower sheet 1. The control unit 14 controls the microcomponents 12 and 13 wirelessly, for instance electromagnetically. To facilitate such control,

the electrically conductive layer 5 of the lower sheet 1 has, in contrast to the electrically conductive layer 8 of the upper sheet 2, two through holes 15 and 16 which are arranged straight under the micropump 12 and the microvalve 13, respectively.

In the embodiment illustrated, a microsensor 17a is arranged in the branch 9a and a microsensor 17b is arranged in the branch 9b. Here the microsensor 17a is a sensor for detecting the fluid, and the sensor 17b a sensor for determining the temperature of the fluid. One of the microsensors, for instance the microsensor 17a, can be replaced with an analytical sensor for analysing the fluid. In this case, the microsensor 17a communicates wirelessly with a computing unit 18 which can receive analysis data from the analytical sensor 17a for process- ing, showing, recording and/or storing this data and possibly utilise it in order to control the microcompo- nents 12 and 13 via the control unit 14. The computing unit 18 can be adapted to forward this analysis data, wirelessly or non-wirelessly, for continued processing.

The lower sheet 1 has, in contrast to the upper sheet 2, for reasons of communication two further holes 19 which extend through its conductive layer 3 and are arranged straight under a respective one of the micro- sensors 17a, 17b.

The flow duct system 9 can, of course, be formed in a manner other than illustrated in the drawing. The design of the flow duct system 9, the location of the inlet 10 and the outlet 11 and also the arrangement of microcomponents 12,13 and microsensors 17a, 17b may be varied according to the application in which the device is intended to be used. Moreover the device can be pro- vided with more than one inlet and more than one outlet.

Different fluids can simultaneously be conducted through the flow duct system of the device. These fluids may then, when necessary, be mixed in a microcompartment which is formed in the flow duct system 9.

In some applications, it must be possible to heat a fluid quickly to a predetermined temperature or a predetermined temperature range for the microsensor or microsensors 17a, 17b that are used in the device to function in an optimal manner, or for evaporation of the fluid which when supplied to the flow duct system 9 is in a liquid phase to be provided. Such quick heating can be achieved in the inventive device by the elec- trically conductive layer 5 of the lower sheet 1 being heated inductively or in some other known manner. It goes without saying that such heating can also be achieved by the electrically conductive layer 8 of the upper sheet 2 being heated inductively or in some other manner. Since the layers 3 and 7 of polymer material are very thin (0.1-0.2 mm), the temperature of the fluid supplied to the flow duct system 9 can thus be changed quickly.

The electrically conductive layers 5 and 8 also have the function of shielding the microcomponents 12 and 13 and the microsensors 17a and 17b from any components (not shown) for radiocommunication, which are arranged outside the two sheets 1 and 2.