Abstract:
Disclosed are a method and a device for feeding and/or discharging fluids in microreactor arrays through one or several fluid ducts that extend into each individual microreactor and can be individually controlled and regulated, in order to control, regulate, influence, and/or verify processes. The fed or discharged amounts of fluid are introduced into or discharged from the volume of the reaction liquid during a continuous shaking process and are evenly mixed as a result of the shaking process. The continuous shaking process causes sufficient mass transfer and thorough mixing of the reaction partners or fluids while the reaction is not limited or restricted by the mass transfer conditions.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is the National Stage of PCT/DE2007/001143 filed on Jun. 28, 2007, which claims priority under 35 U.S.C. §119 of German Application No. 10 2006 030 068.8 filed on Jun. 28, 2006. The international application under PCT article 21(2) was not published in English. 
     BACKGROUND 
     The invention relates to a microreactor array, a device comprising a microreactor array, and a method for using a microreactor array. By means, of conventional titer plates it becomes possible to implement microreactor arrays of, for example, 6, 24, 48, 96, 384 or more individual microreactors. Just as the number of microreactors varies greatly, so can the volume of the individual reactors. While the term “microreactors” is used already at scales of below 10 ml, further reduction of the volume to below 1 ml, below 500 μl, below 100 μl or even below 10 μl can be associated with some advantages. The surface-to-volume ratio that has been increased by the volume reduction is larger, and oxygen input into the reaction solution through simple diffusion is simpler. The microreactor arrays can be shaken continuously until the end of the reaction. Individual metered addition makes it possible to carry out various experiments in each individual reactor. The invention is, in particular, also suitable for automating screening experiments in a fedbatch mode, a continuous mode and/or pH regulation. The invention relates in particular to microbial, biochemical, enzymatic and chemical reactions. The invention supports sterile, aseptic or monoseptic operation. 
     Process parameters such as for example the pH value, concentrations of dissolved oxygen, dissolved carbon dioxide, biomass, educt and product, or temperature can be used as controller outputs for controlling the metered addition. Particularly suitable, in the context of the invention, is a non-invasive acquisition of the process parameters with the use of optical or electromagnetic measuring methods through the bottom that is permeable to electromagnetic radiation. 
     In many areas of biology, process technology, pharmacy and medicine, screening of biological systems becomes necessary (e.g. selection of suitable biological strains, enzymes or suitable culture media and culture conditions). In this context there is a need for high sample throughputs (parallelisation of the experiments) and for a reduction in the quantity of reactants, some of which are expensive. 
     By means of the bioreactors in use at present, for example shaker flasks, small-scale fermenters and test tubes, it is not possible to meet this demand. Established techniques do not meet the requirements for automation, cost minimisation and the required high throughput. In particular in the case of biocatalytic systems, there is a requirement to carry out many parallel experiments at the microliter scale, because such processes, generally speaking, progress more slowly and especially in the development phase are more expensive than comparable chemical processes. It is therefore necessary to develop microbioreactors that in the smallest possible space provide a suitable environment for biological cultivation and biocatalytic reactions. In this context two criteria should be underlined as being important prerequisites for suitable operating conditions: the possibility of carrying out the corresponding experiments under sterile or monoseptic conditions, and ensuring mass transfer (liquid-liquid; liquid-gas; solid-liquid; solid-gas) that is suitable and adequate for the biological culture or for the biocatalytic reaction system. 
     Microreactor arrays, for example microtiter plates (MTPs) provide an ideal platform in order to achieve a high number of parallel operations. Due to the small reaction volumes (e.g. &lt;10 μL to &gt;5 mL per chamber), the high number of parallel operations (e.g. 6 to 1536 chambers per plate) and the option of automating the cultivation processes (in a form that can be handled by robots), microreactor arrays represent the bioreactor that overall is most cost-effective and that has the most promising future. Furthermore, the use of non-invasive optical measuring methods in order to acquire process variables is already quite advanced in this reactor type. Moreover, the operating conditions in shaken MTPs as far as the mass transfer (maximum oxygen transfer capacity) is concerned are already well characterised (Hermann et al., 2002) and are thus comparable to the operating conditions in laboratory reactors, pilot reactors or production reactors. 
     For these very reasons there has recently been an increase in the use of microreactor arrays. At present, microtiter plates are already used for screening biological systems. To this effect the individual reaction chambers are filled, inoculated, and incubated on a rotary shaker. As a result of the shaking movement the feed of oxygen into the reaction fluids is improved, and thorough mixing of the reaction fluids is achieved. Apart from the shaking movement there are other possible options that may be considered for thoroughly mixing fluids in microtiter plates (e.g. moving the fluid by means of sound waves). In order to keep the system sterile, the microtiter plates are covered by an air-permeable membrane (pore size &lt;0.2 μm) or airproof film or foil or a cover construction, or cultivation takes place in an open manner in a sterile environment. 
     In order to carry out the different biocatalytic reactions it is often necessary to add to the ongoing reaction various fluids or gasses while the experiment is ongoing. In this context the supply of pH adjusters (alkaline solutions and acids) for pH titration of the ongoing reaction, and the infeed of substrates should be emphasized. It is only the infeed of substrates during the process that makes it possible to carry out regulated batch, fedbatch and continuous processes. These modes of operation are particularly important for flexible and successful biological screening and for further development of the processes. 
     A brief discussion of the importance of the most important operating methods is provided below. 
     The pH value of a medium is one of the most important environmental influences for cell growth and for the ability of micro-organisms to develop. The activities of the enzymes that catalyse all the reactions due to the metabolic process are decisively influenced by the pH value. However, the pH value of the medium continuously changes as a result of the metabolism of the organisms and as a result of the consumption of the components of the culture medium. If pH regulation is lacking, it is difficult to achieve high cell densities. Therefore regulation of the pH value by titration of pH adjusters (alkaline solution or acid) is necessary. The pH adjuster can be in liquid or gaseous form. 
     In industrial production processes the fedbatch mode (cultivation with the infeed of substrate) is the standard process. The fedbatch mode is necessary in many production processes, for example in order to prevent inhibition as a result of excessive substrate concentrations or catabolite repression. Fedbatch mode must therefore be possible for the corresponding bioreactors. In addition it is precisely in this mode, where the pH value changes greatly, that pH regulation is almost always necessary. 
     Furthermore, continuous reaction management of biocatalytic systems is important in order to achieve a steady state or steady-state balance and in order to determine kinetic parameters, as well as to carry out long-term experiments (e.g. to determine the genetic stability of genetically modified micro-organisms). 
     For many decades, regulating the pH value and carrying out the reactions in fedbatch mode has been the state of the art in large-scale industrial applications. Likewise, commercially available small-scale (&gt;10 mL-500 mL) reactor systems are becoming increasingly widespread (e.g. fedbatch pro by DasGip [U.S. Pat. No. 6,202,713], Sixfors by Infors, etc.). 
     Small-scale reactor systems are used for screening and process development; they can be operated under the above-mentioned conditions. However, the following applies: the smaller the reaction volume, the more elaborate and cost-intensive the implemented solution. Due to the very considerable technical expenditure in the case of small reaction volumes, and due to the low achievable degree of parallel operation in the case of greater reaction volumes, the proposed approaches to this problem are associated with very considerable limitations. For example, in the current approaches it is not possible to have high-throughput screening (&gt;16, &gt;20, &gt;50, &gt;500, &gt;1,000, &gt;10,000 to &gt;100,000 reactions per day) while at the same time providing high-content screening (&gt;1, &gt;2, &gt;3, &gt;4, &gt;5 reaction parameters for each reaction point in time). At present different approaches to finding a solution have been implemented or are pursued to implement the described operational modes in microreactor arrays. Broadly-speaking, a differentiation can be made among contactless, contacting, and microfluidic dosing methods. 
     The technique for contactless metered addition of very small quantities of fluid is largely based on piezo technology. As a result of the very considerable instances of acceleration (up to 100,000 g) that can be achieved by a piezo element, it is possible to separate, and thus to dose, very small droplets (&gt;30 pL) from a reservoir. Various companies (e.g. Nano-Plotter™ by GeSim; Autodrop by Microdrop) market devices for the metered addition of very small volumes of fluid in MTPs. 
     Furthermore, contactless dosing methods exist that are operated with the use of compressed air (e.g. Vieweg GmbH) [EP 1036594]. The achievable droplet volumes range from approximately 5 μL to 0.2 mL. Furthermore, there are patents relating to the cultivation of cells in microreactors with the use of droplet infeed of reaction fluids [DE 10221565, DE 10019862, DE 10046175]. In these approaches the reaction fluids are fed through capillaries to the reaction chamber or above the reaction chamber until at the tip of the capillary a droplet of adequate size has formed, which droplet then drips into the reaction space. In the case of aqueous media the volume of such a droplet is in the order of approximately 20 μL, depending on the diameter and the design of the needles. 
     In contacting dosing methods the infeed of fluids mostly takes place by controlled dipping of pipette tips into the reaction fluids of the individual chambers of the microreactor arrays by way of a pipetting robot. In this process serially (one pipette tip) or in parallel (several pipette tips) the desired quantities of fluids are metered to the individual chambers. By dipping the pipette into the reaction fluid the metered droplet can be separated from the pipette tip so that quantities in the picoliter range can also be dosed [DE 10201749, DE10116642, WO 02/080822]. 
     Utilisation of microfluidic transport in microreactors is not new either. There are already several approaches for transporting and controlling minute quantities of fluid in microreactors, e.g. WO 02/37096, U.S. Pat. No. 6,403,338, EP 1142641, DE 60000109, U.S. Pat. No. 6,268,219, WO 01/68257, US 2005/0032204; US 2005/0084421, WO 02/060582, WO 03/025113, WO01/68257, WO2004/069983. 
     Taking into consideration the current approaches and evaluation of them by applying the criteria of sterile operation of the reaction space, oxygen supply of the biological cultures, and realisation of individual infeed and discharge of fluids, the individual approaches are associated with the following disadvantages. 
     While contactless jet-dosing based on piezo technology makes it possible to dose very small quantities of fluid, these methods are however cost-intensive and prone to malfunction. 
     When compared to piezo-technology-based methods, pressure-driven or gravity-driven methods are more cost-effective, but they are associated with a disadvantage in that only comparatively larger droplet volumes (&gt;5 μl or &lt;0.2 mL) can be dosed. As a result of the volume ratio of the infed droplets to the reaction volume of the individual microtiter plates, at the time of adding a droplet of reaction fluid an extreme increase in the corresponding concentrations in the reaction chambers takes place. As a result of these extreme concentration increases the experiments are considerably influenced so that the analysis results obtained are not representative and cannot be transposed to larger scales. Such extreme increases in concentration can then only be counteracted by an increase in the volume of the culture. 
     Contactless dosing methods are associated with a further disadvantage in that closing off the microreactor arrays by means of a membrane or a cover is either not possible at all or is possible only with very considerable expenditure. Closing them is necessary in order to keep the individual reaction vessels of an MTP sterile or monoseptic, and in order to minimise any evaporation of reaction fluid. 
     Furthermore, contactless dosing methods do not allow dosing during continuous shaking of microreactor arrays. Only intermittent dosing is possible, because any metered addition is only possible after the shaking process has been stopped. However, in the case of biocatalytic reactions non-intermittent metered addition is desirable because as a result of stopping the shaking movement the operating conditions (e.g. interruption of the oxygen infeed and of thorough mixing) undergo a sudden change, and thus any analysis results obtained in this manner can be used only to a limited extent. 
     In the case of contacting dosing methods there is a considerable danger of contamination or cross contamination as a result of the pipette dipping into the reaction fluid. Furthermore, with this method, too, closing the microreactor arrays off by means of a membrane or a cover is prevented, and any metered addition of fluids during the shaking process is likewise not possible. 
     Existing microfluidic approaches relating to the transport and control of minute quantities of fluid in microreactors comprise at least one of the following deficiencies: The methods are not designed to dose variable volumes to individual chambers of microreactor arrays. The methods are exclusively used for the analysis of substances and substance flows, for the separation of substance flows and/or for the preparation of the smallest possible sample volumes. The methods only support even separation of fluid volumes in microreactor arrays. With these methods it is not possible to achieve any targeted metered addition to individual chambers. The methods do not allow any sterile closing off of the microreactor arrays by means of a membrane or a cover. The methods do not support the metered addition or discharge of fluids during continuous shaking of the microreactor arrays in order to thoroughly mix the reaction fluids and in order to set adequate mass transfer rates. 
     In summary it can be stated that none of the approaches mentioned above make it possible to unify the following requirements of a biotechnological, biochemical or chemical process:
     1. individual infeed and discharge of fluids into and from the individual reaction chambers of a microreactor array (e.g. in order to implement pH titration or a fedbatch process);   2. sterile or monoseptic closing-off of the microreactor array during infeed or discharge of fluids;   3. adequate and controlled mass transfer (e.g. for the supply of oxygen) by means of shaking.   

     SUMMARY 
     Based on this state of the art it is the object of the invention to remove some of these limitations for microreactor arrays. For, already at the smallest scale of primary screening the operating conditions should be as similar as possible to those of subsequent production, because otherwise selection would take place according to incorrect criteria. An incorrect selection of catalysts (strains, enzymes, proteins or chemical catalysts) in primary screening due to unsuitable test conditions has an effect on the entire subsequent process development and as a rule can no longer be compensated for. The economic disadvantages are likely to be considerable, but they cannot be quantified because up to now no suitable techniques were available at the microscale that would, for example, make possible pH control and fedbatch operation in primary screening. 
     In order to implement such operating methods in microreactor arrays, due to the small reaction volumes, feeding and discharging the fluid quantities needs to take place in the nano- or picoliter range. This is necessary in order to appropriately influence or regulate the processes and in order to, if necessary, achieve the same ratios of fed-in or discharged volumes to reaction volumes as is the case in larger reactors. In this way scale-up of the results of the analysis can be made possible. 
     The object is met by a microreactor array comprising several containers and at least one duct that forms a fluid line to the container. 
     The microreactor array according to the invention supports a fluid system for the infeed and discharge of fluids. A fluid system is defined as a device comprising a duct system that provides various ducts on one plane or on several planes, through which ducts the desired fluids are conveyed. Furthermore, the fluid system preferably comprises valves that can close off the individual ducts, thus allowing control of the fluid ducts. If the ducts for conveying fluid and if the actuators or control devices for the valves are implemented on different planes or substrates, these planes are referred to as control planes. Through the fluid ducts the fluids are individually conveyed to the individual reaction chambers. By means of a concurrent shaking process of the microreactor array, the fluid quantities conveyed to the reaction chambers can mix with the remaining reaction volumes. By means of controlling the individual inflows to the various reaction chambers of the microreactor array, individual inflow and outflow can be implemented. 
     Controlling the individual fluid ducts can be implemented by various methods. Among other solutions, pneumatic control ducts are imaginable which extend at right angles to the fluid ducts on a different plane and which when subjected to pressure can squeeze and close off the desired fluid duct by means of a thin membrane. However, optically, thermally, electromechanically or magnetically actuated microvalves can be used for controlling the fluid ducts. In order to minimise any diffusion of the reaction media within the reactor, back into the fluid ducts, simple passive valves can be implemented at the inlet of the duct into the reactor. 
     In addition, the fluid ducts and reactor chambers can be designed such that they are at least partly permeable to electromagnetic radiation (for example light). In this way electromagnetic or non-invasive optical reaction monitoring is made possible. Depending on the measuring task at hand, the fluid system can be designed as the lid, the bottom or the mid-plane of the microreactor array so that access to the microreactors is provided from the top or from the bottom. 
     In its various embodiments the invention provides the following advantages when compared to hitherto-implemented approaches: 
     Individual feed and discharge of reaction fluids to and from the individual chambers of the microreactor arrays is made possible. 
     The feed and discharge of reaction fluids can be implemented such that optical access to each individual chamber of the microreactor array remains ensured. In this way the operating states can be determined in a non-invasive manner in each individual chamber by optical measurements. 
     Individual metered addition and data acquisition can make it possible to regulate controller outputs for each individual reaction chamber. 
     Metered addition can take place without the need to interrupt the shaking process. 
     The reaction chambers can be closed off with a gas-permeable membrane or a gas-permeable cover. This makes possible sterile operation and minimises evaporation, as a result of which the reaction volume can be kept largely constant. 
     When compared to the state of the art, the arrangement according to the invention and improvements to this arrangement overcome the following disadvantages: 
     The very small quantities (&gt;10 μL) of fluids (e.g. pH adjusters, substrate) that are required in the individual reaction chambers can be fed to and discharged from the individual chambers in a sterile manner. 
     The reaction chambers can be closed off in a sterile manner by a semi-permeable membrane or a cover. 
     Adding the fluids can take place without the need to interrupt any shaking process. The supply of oxygen to the organisms contained in the chambers is thus not interrupted, and continuous thorough mixing of the fluids, solids and gases is ensured. 
     In relation to its form and applicability, the system can be based on commercially available microtiter plates. 
     The methods and devices described in the claims disclose further combinations of features that per se are significant in the context of the invention and that also in any further combination among themselves and also in connection with previously-mentioned features describe aspects that are significant in the context of the invention. 
     It is advantageous if in the microreactor arrays each container comprises a duct. In this way the different containers can receive their supplies individually. In particular for feeding and discharging fluid it can be advantageous if the containers are connected by means of at least two ducts. 
     This results in a microreactor array in which one or several fluid ducts leads/lead to each individual microreactor. Consequently, the microreactor array can be individually controlled and/or regulated. This makes it possible to provide process management, process regulation, process influencing and/or process control. 
     An exemplary embodiment provides for the containers to be arranged in one plane, and for the duct to be arranged in the plane of the containers. To this effect the duct can, for example, be implemented in the sidewalls of the microreactor array. The fluids to be dosed are consequently no longer in constant contact with the fluid in the microreactors. In this arrangement, as a result of the fluid crescent generated by shaking, the droplet presented through the fluid duct is separated from the sidewall and is taken up by the reaction fluid. 
     Another embodiment variant provides for the containers to be arranged in one plane, and for the duct to be arranged underneath the plane of the containers. 
     In particular if the microreactor array comprises a cover, it is advantageous if the containers are arranged in one plane and if the duct is arranged above the plane of the containers. In this way the fluid ducts can be implemented in the cover of the microreactor array, and the fluids to be dosed are consequently in permanent contact with the fluid in the microreactors. In this embodiment, too, the droplet presented through the fluid duct is removed from the cover as a result of the fluid crescent that is generated by the shaking movement and that extends to the cover, and is taken up by the reaction fluid. 
     The microreactor array can also be designed such that the fluid ducts for the infeed of fluids are implemented in the cover of the microreactor array, and such that the exits of the fluid ducts do not establish contact with the fluid in the microreactors. The fluid droplets are then removed as a result of considerable acceleration, and are fed to the reaction fluid. 
     It is understood that various ducts can also be arranged in different positions relative to the plane of the containers. 
     In order to implement different microreactor arrays it is thus advantageously proposed that the transition between the duct and the container be arranged above the fill plane of the container, and that the array comprises a cover in which the duct is arranged. 
     It is advantageous if the microreactor array comprises a valve and/or a pump. A valve makes possible the controlled supply of fluids, while a pump provides the necessary increase in pressure in order to convey fluids into the reaction chambers. The exemplary embodiments shown explain that a valve can also be further developed in a simple manner so that it becomes a pump. 
     In order to control the valve or a pump, a focused light beam, thermal control or control by way of microwaves is proposed. A light beam can also be focused on or guided to the respective valves by way of wave guides which, in particular, are integrated in the control plane. Thermal excitation can, for example, be implemented by means of an electrical heating coil. Further options involve magnetically or inductively controlled valves and pumps. 
     Furthermore, by way of transitions of hydrophilic and hydrophobic surfaces the duct can assume a valve function. This results in passive valves for controlling the fluids. 
     It is proposed that the duct comprises thermally or electrically shape-changing materials. Thermally shape-changing polymers and/or metal alloys can be used for this purpose. Furthermore, shape memory alloys (SMAs) and shape memory polymers or electrically shape-changing ceramics (piezo crystals) can be used in the implementation of valves and pumps. 
     One embodiment provides for the duct to comprise a wall as a valve or pump, which wall is deformable by pressure. As a result of controlled pneumatic or mechanical pressure from the outside, one of the sides of the fluid duct can be pushed into said fluid duct in order to close it off, thus implementing an active valve function or a pump function. 
     The valves or pumps used in the fluid system can also comprise a film or foil, or a thin substrate that interacts with an electrical circuit that is used as a control plane of the fluid system. 
     One embodiment provides for indentations on the array to be designed as pneumatic connections. Such indentations and preferably one or several reaction chambers, in particular of a microtiter plate, can be used on a microreactor array as pneumatic connections for controlling the fluid flows. 
     In particular if pressure is applied to a deformable wall, in the case of a multiple series connection a peristaltic pumping effect can be generated, wherein the pressure acting onto one side of the fluid duct can be generated pneumatically or mechanically. 
     In particular if the fluid ducts are implemented in the bottom of the microreactor array, the fluids to be dosed, separated by a valve, can be in contact with the reaction fluid in the microreactors. An alternative provides for the fluids to be dosed to be separated from the reaction fluid in the microreactors by means of a partially permeable membrane. To this effect a partially permeable membrane is arranged in the duct or in the container. 
     It is advantageous if at least one surface of the array is designed to provide optical access. With the use of suitable materials at least one surface of the individual microreactors as an optical access can make possible the individual acquisition of data from the individual microreactors, which data can be used for controlling the processes. 
     Furthermore, it is advantageous if the microreactor array comprises sensors, in the individual containers, for the acquisition of data. In this arrangement, different sensors, and in particular also chemical sensors in dissolved or immobilised form, can be used, in the individual microreactors, for the individual acquisition of data. 
     One exemplary embodiment provides for containers of the microreactor array to comprise a form or surface structure that is suitable for minimising any contact between the fluid and the duct. As a result of a special form of the individual microreactors, or additional structures contained in them, minimising the contact between the fluid crescent and the exit of the fluid duct, diffusion of the fluid into the ducts can be prevented. 
     The object on which the invention is based is also met by a device comprising a microreactor array, which device comprises a movement device. Such a movement device can be a mechanical shaker, a stirrer or an ultrasound device. 
     It is advantageous if the movement device drives at least one pump that is integrated in the microreactor array. Such a pump can increase the pressure in a fluid duct, which pressure ensures conveyance of the fluid after a valve has been opened. 
     One embodiment provides for the duct to be designed and to be arranged relative to a container comprising reaction fluid such that a quantity of fluid at the end of the duct is only taken by the crescent of the fluid surface when the reaction fluid is moved. 
     It is advantageous if the device comprises a microtiter plate and a control plane with valves. Apart from valves for controlling through-flows, the control plane can also comprise pumps for the actual conveyance of fluid. On the other hand the control plane can also comprise only valves for controlling through-flows, wherein the actual mass conveyance is implemented by external pumps or pressurisation. 
     Dividing the microtiter plate and the control plane makes it possible to use microreactor arrays that are based on the standard format for microtiter plates. In this way the microtiter plate can be supplemented by a fluidic dosing system. On the other hand a microtiter plate can also itself form part of the fluid system and can be supplemented only by a control plane. It is advantageous if the control plane comprises an electrical circuit. 
     Furthermore, it is proposed that a fluid plane and a control plane are combined in a modular manner. In this way reuse of the complex control plane is ensured, while the fluid plane can be produced as a sterile single-use product. 
     The object on which the invention is based is also met by a method for using a microreactor array for feeding and/or discharging fluids in microreactor arrays through one or several fluid ducts that lead to individual microreactors. Providing the fluid ducts makes it possible to individually control or regulate the fluid ducts. Furthermore, the fluid quantities fed or discharged can be introduced into or withdrawn from the volume of the reaction fluid during a mixing process. A continuous shaking process can ensure adequate mass transport and thorough mixing of the reaction partners or of the fluids. In this process the reaction of the reaction partners is not limited by conditions relating to the metabolic process. 
     One embodiment of the method provides for a quantity of fluid to be kept at the duct and to be taken only when the reaction fluid is moved through the crescent of the fluid surface. 
     A particular procedure of the method provides for the required fluid quantities in a first step to be placed into a fluid reservoir provided for this purpose by means of conventional dosing methods such as micro- or nanodispensing, and in a subsequent second step for the access ports for dosing to be sealed off so as to be pressure-proof, and for the predosed quantities of fluid to be pushed at overpressure through the membranes and into the microreactors. In a special procedure of the method, until the end of the reaction of the reaction partners, the reaction space in each microreactor is at each point in time closed either by a membrane or a cover and/or by the fluid-filled fluid systems, in order to in this way prevent any uncontrolled infeed or discharge of matter or contamination. 
     Furthermore, it is proposed that the microreactor array be covered up by a membrane or a cover, and that all the fluids to be fed and discharged be guided through pre-sterilised materials so as to keep the entire reaction procedure sterile or monoseptic. 
     Furthermore, the fluids to be fed can be kept ready in an indentation, preferably of one of the reaction chambers on the microreactor array, or in some other receiving vessel that is connected to feed lines. The fluids to be fed can also be kept ready in a separate container that is not being shaken as well, and can then be fed to the individual microreactors by way of ducts or tubes. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
       In each case the figures diagrammatically show exemplary embodiments of the invention, further inventions and combinations of features according to the invention. 
         FIG. 1  shows various options of implementing a microreactor array; 
         FIG. 2  shows reservoirs that are connected to the reactors of the microreactor array by way of tubes or flexible fluid ducts; 
         FIG. 3  shows closing off individual or several fluid ducts that lead to a reactor; 
         FIG. 4  shows that with a clever arrangement of fluid ducts of the fluid plane and of the pneumatically actuated membranes the fluid pressure or gas pressure in a branch of the fluid duct can be increased; 
         FIG. 5  shows the use of a semi-permeable membrane at the transition from the fluid duct to the reaction chamber; 
         FIG. 6  shows another cross-sectional view; 
         FIG. 7  shows a sidewall feed device; 
         FIG. 8  shows a further variant of the microreactors wherein the fluid to be dosed is presented through an opening in the cover; 
         FIG. 9  shows the fluid crescent does not extend to the cover; 
         FIG. 10 , in this manner a cover can individually supply the most minute quantities of fluid to any number of microreactors; 
         FIG. 11 , the individual fluid prechambers  11  are filled by capillary action this volume reduction can be implemented by the heating elements shown in  FIG. 11A , or by the piezo crystals shown in  FIG. 11B ; and 
         FIG. 12  shows a duct extension to protruding from the cover into the fluid within the reactor where, as shown it is in permanent contact with the fluid; 
         FIG. 13  shows a semi-permeable membrane affixed to the underside of the cover, can be used; 
         FIG. 14  shows an arrangement in which the microreactor array with its individual reactors is decoupled from the laser light source; 
         FIG. 15  A shows how in a first step the respectively required quantity of fluid is filled into the corresponding fluid prechambers by means of a micro- or nanodispenser 
         FIG. 15B  shows how the dosing openings  21  are closed after the filling procedure, with pressure is applied to the fluid ducts and the fluid prechambers by way of a pneumatic system; 
         FIG. 16A  shows a fluid- and reactor plane comprises three components: a bottom with the reactor chambers and the fluid ducts; 
         FIG. 16B  shows these access ports, are used in order to connect to the membrane the actuator arrangement that is affixed to a cover; 
         FIG. 16C  shows this droplet is sheared off from the fluid crescent; 
         FIG. 17  diagrammatically shows a regulating principle which would, for example, be suitable for a pH-controlled procedure of the analysis; 
         FIG. 18  illustrates one embodiment of the design, wherein the fluid to be dosed is presented through an opening in the reactor bottom; and 
         FIG. 19  shows the fluid to be dosed is presented through an opening at half the reactor height 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows various options of implementing a microreactor array  1  that is based on a standard microtiter plate format. In this arrangement it is not mandatory for the geometric arrangements of the individual reactors  2  to be circular. The use of the standardised microtiter plate format ensures unimpeded compatibility with conventional pipetting robots. It is also possible to implement reservoirs  3  on the plate that keep ready the fluids to be fed. Apart from designing the reservoir  3  and the microreactor  2  so that they differ in shape, they can also be identical in shape. For example, in existing microreactor arrays some microreactors  2  can be used as reservoirs  3  for the fluids to be transported. These reservoirs  3  can be implemented on the microtiter plate in any shape and position. 
     In many cases it may be sensible to keep the fluids that are to be fed to the reactors  2  or that are to be discharged from said reactors  2  ready in separate reservoirs  3  that are not being subjected to shaking. These reservoirs are then connected to the reactors of the microreactor array by way of tubes or flexible fluid ducts  4  as shown in  FIG. 2 . 
     Closing off individual or several fluid ducts  4  that lead to a reactor  2  can, as shown in  FIG. 3 , be implemented by means of thin membranes  8  that are pressurised with compressed air through a pneumatic duct  7 , that push into the fluid duct  4  and in this way close off said fluid duct  4 . In the example shown, the fluid plane  5  and the pneumatically actuated control plane  6  form part of the bottom of the microreactor array  1 . The valves shown in the diagram only have control functions. The actual mass transport can be implemented by external pumping devices. 
       FIG. 4  shows that with a clever arrangement of fluid ducts  4  of the fluid plane  5  and of the pneumatically actuated  7  membranes  8  the fluid pressure or gas pressure in a branch of the fluid duct  4  can be increased and at the same time further supply ducts can be closed. For example, by way of a single membrane  8  in a single step a duct can be pressurised while other fluid ducts  4  are being closed. 
       FIG. 5  shows the use of a semi-permeable membrane  10  at the transition from the fluid duct  4  to the reaction chamber  2 . In a simple manner it can minimise any uncontrolled diffuse mass transfer from the duct to the reactor and vice versa. An actuator  9  (e.g. piezo crystal, shape memory alloy, shape-changing polymers, etc.), or a pneumatic duct  7  that is separated by a membrane, provides the pumping capacity required in order to push the medium in the fluid prechamber  11 , which medium is to be fed, through the membrane  10  and into the reaction chamber  2 . 
     Apart from the implementation of a duct feed device  4  in the bottom, a sidewall feed device, shown in  FIG. 7 , can also be sensible. In order to present a droplet on the inside of the reactor  2 , so that said droplet is carried along by the crescent generated by shaking, in this arrangement, too, the already mentioned valve techniques or pumping techniques can be used. In this duct arrangement  4 , too, the fluid ducts can be controlled by way of pneumatic control ducts or some other actuator arrangement  9  (e.g. shape memory alloys or shape-changing polymers etc.). 
     Targeted surface treatment of the ducts  4  provides a further option of controlling the fluid flows within the fluid plane. With the transition from hydrophilic to hydrophobic surfaces it is possible to create simple barriers to the fluid flow. In the example shown, such a barrier  13  prevents the fluid from the side duct  4  from flowing into the vertically extending main duct  4 . By means of brief pressurisation this barrier  13  can be overcome. Once contact with the main flow has occurred, just a brief interruption of the main flow (e.g. by air bubbles) can again restore the function of the barrier  13 . An additional air inlet at the location of the barrier can also cause the inflow from the side duct to cease after a drop in pressure. 
     In a further variant of the microreactors the fluid to be dosed is presented through an opening in the cover, as shown in  FIG. 8 . Apart from the fluid ducts  4  through which the fluid is conveyed to the individual reactors  2 , the cover also comprises aeration inlets with special membrane inserts  15  in order to ensure sterile gas supply if this is required for the process. To ensure that the droplet presented by the duct  4  can also be taken up in small quantities by the fluid, the fluid crescent  12  generated as a result of shaking needs to extend right up to the fluid duct inlet. 
     In the case, shown in  FIG. 9 , where the fluid crescent  12  does not extend to the cover, the droplets detached from the fluid duct  4  need to be accelerated considerably so that the volume of the droplets is kept as small as possible. This approach circumvents the above-mentioned disadvantages of contactless dosing methods. In this embodiment the dosing unit forms part of the cover and can be shaken along with the microreactor array. For this reason, too, the cover needs to comprise fluid ducts  4  and aeration inlets  15  to the individual reactors. 
     As shown in  FIG. 10 , in this manner a cover can individually supply the most minute quantities of fluid to any number of microreactors. As shown in  FIG. 11 , the individual fluid prechambers  11  are filled by capillary action. Due to the very small opening to the reaction chamber  2 , no droplets detach as a result of surface tension. It is only as a result of fast actuation that reduces the volume of the fluid prechamber  11  that minute droplets are shot into the reaction chamber. This volume reduction can be implemented by the heating elements  16  shown in  FIG. 11A , or by the piezo crystals  17  shown in  FIG. 11B . 
     Instead of the use of highly accelerated droplets for dosing minute quantities of fluid, it is also possible for a duct extension to protrude from the cover into the fluid  12  within the reactor  2 , where, as shown in  FIG. 12 , in permanent contact with the fluid  12 , said duct extension ensures the feed or discharge of further media. Any unwanted diffusion into the fluid duct  4  or out of it can to a very large extent be minimised by a very small opening or by a semi-permeable membrane. 
     A semi-permeable membrane  10 , affixed to the underside of the cover, can be used twofold. As shown in  FIG. 13 , on the one hand said semi-permeable membrane  10  ensures sterile oxygen exchange at the aeration inlets  15 , and on the other hand it enables better control of the fluid infeed through the fluid duct  4 . Said semi-permeable membrane  10  prevents diffuse thorough mixing in the fluid duct  4  and allows fluids to pass only if the duct is slightly pressurised. 
     Many materials such as solid polymers or encapsulated polymer gels or metal alloys, which can be used for actuation, in other words as a pump or valve, can be influenced and controlled  20  by electromagnetic waves such as laser light. The example shown in  FIG. 14  describes an arrangement in which the microreactor array  1  with its individual reactors  2  is decoupled from the laser light source  18 . The microreactor array  1  is shaken, while the stationary laser  18  is focused on a particular point. In order to activate, by means of light, the region to be actuated, either the shaking radius can be selected to be sufficiently small so that the targeted region is never entirely out of focus, or that during the shaking movement said shaking radius is always guided by the laser focus  19 . While in this way it is not possible to implement continuous radiation, in most cases, however, pulsed energy input is quite sufficient in order to achieve the desired effects. 
     Another approach consists of implementing the dosing and infeed of fluids to the individual reactors  2  in two steps that are independent of each other.  FIG. 15  A shows how in a first step the respectively required quantity of fluid is filled into the corresponding fluid prechambers  11  by means of a micro- or nanodispenser  22  (e.g. pipetting robot) that travels in the x-y plane. In this arrangement the dosing openings  21  should be selected to be large enough so that the dispenser as a stationary dosing unit  22  need not retrace the shaking movement of the microreactor array  1 . By means of a mechanism the dosing openings  21  are closed after the filling procedure, and, as shown in  FIG. 15B , pressure is applied to the fluid ducts  4  and the fluid prechambers  11  by way of a pneumatic system  7 . This pressure ensures fluid transfer through a semi-permeable membrane  10 . The membrane  10  (pore size &lt;0.2 μm) ensures sterile fluid feed. 
     For commercial application a system is advantageous in which the sterile fluid ducts  4  and the actuators are implemented in systems that are separate of each other. The advantage stems from the re-usability of the expensive actuator arrangement, while the fluid ducts and the reactors can be used as sterile single-use or disposable products. The design, shown in  FIG. 16A , of the fluid- and reactor plane comprises three components: a bottom with the reactor chambers  2  and the fluid ducts  4 ; a thin flexible membrane  8  with recesses at the positions of the reactors  2 ; and a top fixture that comprises direct access ports to the reactors  2  in order to fill them and in order to ensure the supply of oxygen during the experiments. In addition, the top fixture also comprises access ports  23  to the membrane  8  above the fluid ducts  4 . These access ports  23 , shown in  FIG. 16B , are used in order to connect to the membrane the actuator arrangement  9  that is affixed to a cover  14 . Simple self-adjustment of the cover  14  is ensured by means of conical access ports. The actuator arrangement situated in the cover makes it possible to press the membrane into the fluid duct  4  situated underneath it, thus closing off said fluid duct  4 . The fluid system  4  first fills itself by capillary action, and after the access ports to the individual reactors  2  have been closed, is pressurised. This pressure can be generated in the cover itself, or it can be generated by external pumps. As a result of a brief opening action of the fluid ducts  4 , a small droplet arises on the reactor wall. This droplet is sheared off from the fluid crescent  12  shown in  FIG. 16C  and is taken along. 
       FIG. 17  diagrammatically shows a regulating principle which would, for example, be suitable for a pH-controlled procedure of the analysis. The pH value in the shaken reactors  2  can be read individually from the outside in a non-invasive manner with the use of optical measuring methods  24 . To this effect so-called optodes  25  can be used. The measured value can be acquired and evaluated continuously. By way of a control circuit, the infeed of corresponding adjusters is then controlled. Such a solution can be implemented equally for a substrate—or for some other substance-infeed and fluid discharge. In this case all the process parameters (e.g. pO2, pCO2, T, biomass concentration, etc.), which process parameters have been acquired optically or electrically from the reaction system, can be used as control variables, or as an alternative, the fluids to be fed or discharged are fed or discharged according to a predetermined profile, or as a single pulse or as repeated pulses. 
       FIG. 18  again illustrates the primary design of the invention. The fluid to be dosed is presented through an opening in the reactor bottom. A plane underneath the reactor bottom comprises the fluid ducts  4  through which the fluids are conveyed to the individual reactors  2 . A gas-permeable membrane  15  can ensure sterile gas infeed to the reactors. The droplets presented through the fluid ducts are taken up into the fluid by the fluid crescent  12  generated by the shaking movement. 
     In the variant of the microreactors, which variant is shown in  FIG. 19 , the fluid to be dosed is presented through an opening at half the reactor height. A mid-plane comprises the fluid ducts  4  through which the fluids are conveyed to the individual reactors  2 . A gas-permeable membrane  15  can ensure sterile gas infeed to the reactors. The droplets presented through the fluid ducts are taken up into the fluid by the fluid crescent  12  generated by the shaking movement. 
     
       
         
               
             
               
               
               
             
           
               
                   
               
               
                 List of reference characters 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                   
                  1 
                 Microreactor array 
               
               
                   
                  2 
                 Microreactor 
               
               
                   
                  3 
                 Reservoir for fluids to be fed or discharged 
               
               
                   
                  4 
                 Fluid duct/tube connection 
               
               
                   
                  5 
                 Fluid plane 
               
               
                   
                  6 
                 Control plane 
               
               
                   
                  7 
                 Pneumatically controlled duct 
               
               
                   
                  8 
                 Flexible membrane 
               
               
                   
                  9 
                 Actuator of any design 
               
               
                   
                 10 
                 Semi-permeable membrane 
               
               
                   
                 11 
                 Fluid prechamber 
               
               
                   
                 12 
                 Fluid crescent 
               
               
                   
                 13 
                 Modified surface 
               
               
                   
                 14 
                 Cover of the microreactor 
               
               
                   
                 15 
                 Aeration inlet to the reactor 
               
               
                   
                 16 
                 Heating elements 
               
               
                   
                 17 
                 Piezo element 
               
               
                   
                 18 
                 Laser 
               
               
                   
                 19 
                 Focused laser beam 
               
               
                   
                 20 
                 Electromagnetically or thermally actuated material 
               
               
                   
                 21 
                 Dosing opening 
               
               
                   
                 22 
                 Dosing unit/pipetting robot 
               
               
                   
                 23 
                 Adjustment openings 
               
               
                   
                 24 
                 Optical reading unit 
               
               
                   
                 25 
                 Optode (varies its fluorescence characteristics 
               
               
                   
                   
                 depending on chemical variables, e.g. pH value) 
               
               
                   
                 26 
                 Control unit/computer