Micro organism cultivation device

In the micro organism cultivation device of this invention, an implantable bio-artificial micro device, i.e., a cell apartment, is provided to cultivate cells or tissues. The cells or tissues to be cultivated include that secrete hormones such as islets of Langerhans. At both sides of the cell apartment, provided are microfluidic channels comprising dynamic micro-electric field array filters. The dynamic micro-electric field array filters comprise a plurality of electrodes distributed inside the microchannels. By periodically switching the polarity of the electrodes, microfluidic flows are generated in the microchannels. All inlet flows to the cell apartment are filtered by the immunoisolation of the micro-electric field array filters before entering into the cell apartment. The micro-electric field array filters provide a physical immune protection to the cells cultivated in the cell apartment against the immune system of the host. The microfluidic flows driven by the micro-electric field array accelerate the release of the hormones secreted by the cells cultivated in the cell

DETAILED DESCRIPTION OF INVENTION FIG. 1 illustrates the plan view of the micro organism cultivation device of this invention. As shown in this figure, the micro organism cultivation device of this invention comprises a microchannel 1 , a cultivation module 6 in said microchannel 1 , a first electrode array 2 and 3 , and a second electrode array 4 and 5 , both positioned beside the cultivation module 6 . The microchannel 1 may be prepared in a substrate (not shown), allowing a microfluid, such as the blood, to pass through. The cultivation module 6 is provided in the microchannel 1 to contain living cells 7 to be cultivated. The fist electrode array 2 and 3 functions as an electro-hydrodynamic pump and an immunoisolation filter for the inlet microfluid simultaneously. The second electrode array 4 and 5 , on the other hand, functions as an electro-osmosis pump for the outlet microfluid. The cultivation module 6 of this invention comprises a microfabricated rigid geometric structure and functions as a cell apartment, such that micro organisms 7 (such as islet cells) may be cultivated inside the cell apartment. In general applications, the surface of the cell apartment 6 may be coated with bio-compatible materials, such as Parylene-C. The first electrode array comprises a positive electrode array 3 and a negative electrode array 2 . Both the positive electrode array 3 and the negative electrode array 2 comprise a plurality of pillar electrodes distributed in the microchannel, in an interlock arrangement. In some other embodiments of this invention, the electrode arrays 2 and 3 are prepared with electrode strips, electrode plates or electrode forks. When a voltage is applied to the first electrode array 2 and 3 , electron flow circles will be formed between the positive electrode array 3 and the negative electrode array 2 , through the microfluid therebetween. The electron flow circles will carry the fluid at the circumstance to flow along the direction of the electron flow and an EHD pumping effect is carried out. At the same time, the micro-electric field among the electrodes of the negative electrode array 2 forms a capture net to intercept the IgG, cytokine particles and the chemokine articles that carry negatives. In other words, the electro-hydrodynamic pump provides driving forces to the inlet microfluid and functions as an immunoisolation filter for the inlet microfluid simultaneously. The second electrode array 4 and 5 functions as the driving force provider for the outlet fluid from the cultivation module 6 . The second electrode array 4 and 5 comprises a negative electrode 4 and a positive electrode 5 . In this embodiment, both electrodes comprise a metal strip affixed to the wall of the microchannel 1 , perpendicularly to the direction of the micro-flow inside the microchannel 1 . When a negative voltage is applied to the negative electrode 4 and a positive voltage is applied to the positive electrode 5 , opposite charges are formed in the solution near the channel wall, whereby a local electrical gradient is formed. The charges in the microfluid can then be moved under the external applied electric field, in turn, drive the microfluid to flow from electrode 4 to electrode 5 . As a result, the second electrode array 4 and 5 functions as an electro-osmosis pump for the microfluid inside the microchannel 1 . Due to the electro-osmosis pump 4 and 5 , the hormone secreted by the cells 7 (such as islet cells) inside the cell apartment 6 may be transported to outside the cell apartment 6 . In this embodiment, the electro-osmosis pump 4 and 5 functions as the major driving force provider for the microfluid in the microchannel 1 . In the embodiment shown in FIG. 1 , the micro organism cultivation device comprises two groups of electro-hydrodynamic pumps 2 , 3 and 8 , 9 and two groups of electro-osmosis pumps 4 , 5 and 10 , 11 . A controller (not shown) may be used to control the application of voltages to these pumps to generate driving forces to the microfluid in the microchannel 1 with different directions, as shown by separate arrows in FIG. 1 . The flow directions of the microfluid in the microchannel 1 may be controlled as shown in the following Table I. 2 TABLE I Electro-hydro- Electro-osmosis dynamic pump pump Flow 2 3 8 9 4 5 10 11 direction − &plus; − &plus; A→B − &plus; − &plus; B→A When the driving mode of the microfluid is from A to B, among electrodes 2 and 3 of the electro-hydrodynamic pump left to the cultivation module 6 is generated a local micro-electric field to function as an immunoisolation for the cultivation module 6 . As the micro organisms 7 are positioned between electrodes 4 and 5 , released articles secreted by the micro organisms 7 , such as insulin, may be easily transported to the microchannel 1 by the electro-osmosis effects of these electrodes 4 and 5 . At the same time, no voltage is applied to the other group of electro-hydrodynamic electrodes 8 and 9 , whereby no articles will be captured by the electric field generated by electrode array 8 and 9 . The article secreted by the micro organisms 7 may be released to the microfluid. On the other hand, when the driving force is from B to A, as shown in FIG. 1 , an immunoisolation is generated at the right side of the cultivation module 6 by electrode array 8 and 9 . As the micro organisms 7 are positioned between electrodes 10 and 11 , the electro-osmosis pumping force generated by electrodes 10 and 11 drives the microfluid so to transport articles secreted by the micro organisms 7 out of the cultivation module 6 . At this time, electrode array 2 and 3 is not supplied a voltage, whereby no articles will be captured by the electric field to be generated. The secreted articles may thus be easily released to the microfluid. In the application of the micro organism cultivation device of this invention, an external power supply controller (not shown) is used to cyclically switch the flow direction of the microfluid. As a result, all inlet flow of the microfluid into the cultivation module is filtered by the micro-electric field immunoisolation provided by the electro-hydrodynamic electrode array. All outlet flow of the microfluid, on the other hand, is driven by the electro-osmosis pump from either direction. FIG. 2, a through f, shows the flow chart of the preparation of the micro organism cultivation device of this invention. As shown in this figure, the micro organism cultivation device of this invention may be prepared according to the following steps: Step a, preparation of chip: At step a, a substrate is prepared and a deep microchannel is formed in the substrate. The substrate is preferably a silicon substrate. A SiN 4 mask layer is formed on the substrate and the substrate is etched in a KOH, THAM (tetramethyl ammonium hydroxide) or EDP (ethylene diamine pyrozine) H 2 O solution until a microchannel with necessary depth (e.g., 200-300 nm) is formed. Step b, preparation of electrodes and cultivation module: At step b, the SiN4 mask layer is removed with a H 3 PO 4 . A Cr and Au layer is sputtered on the substrate to function as the seed layer of the electrodes. Spin coat a thick photoresist layer. The photoresist layer shall be able to cover the seed layer such that the matrix pattern of the structure of the cultivation module may be prepared with the micro-lithographic technology. Thereafter, electroplate Au to the seed layer to form the cultivation module. The height of the Au layer may be about one third to one half of the depth of the microchannel. Step c, preparation of electro-hydrodynamic electrodes: The thick photoresist is removed. Spin coat a thick photoresist layer. Again, this photoresis layer shall totally cover the seed layer. The matrix pattern of the electro-hydrodynamic electrodes is prepared with the micro-lithographic technology. Thereafter, Au is electroplated to form the electrodes. Step d, preparation of electro-osmosis electrodes: The photoresist is removed. Spin coat a thick photoresis layer. This photoresist is required to totally cover the seed layer. The pattern of the electro-osmosis electrodes is prepared with the micro-lithographic technology. The product is subject to etching of the Cr and Au layer to form the electrodes. Step e, formation of insulation layer: The photoresist is removed. Deposit a paryline high molecular insulation layer 17 with the chemical vapor deposition technology. Such an insulation layer provides the conformal deposition effects to the high-depth pattern of the structure. Step f, cover: At step f, a glass layer 18 prepared with through holes for lead pads or for the entrance of the micro organisms is anode bonded with the chip prepared in the previous step. A micro organism cultivation device is thus prepared. 
 EFFECTS OF INVENTION In the micro organism cultivation device of this invention, the rigid structure prepared with the semiconductor process provides an uniformed and accurately defined geometric arrangement to cultivate the micro organism. Such arrangements help to improve the affixation of the cultivated micro organisms to the cell apartment and the stability of their biological functions. In the present invention, the inlet flow and the outlet flow are separately treated. All inlet flows in either direction are subject to the immunoisolation provided by the micro electric field generated by the electro-hydrodynamic electrode arrays and all outlet flows are driven by the electro-osmosis electrodes, each having its respective operation. As a result, different standards are applied to the treatments of the inlet flow and the outlet flow separately. Such a design provides a breakthrough to the paradox of the conventional art. As in an embodiment of this invention, the microfluidic flow is cyclically shifted in directions. It is thus possible to avoid accumulation of blood corpuscles, protein molecules, antibodies and cell hormones at the micro electric field immunoisolation area. It is also possible to accelerate the supply of nourishments to the cultivated cells, the ventilation of wastes and the release of hormones such as insulin. In some embodiments of this invention, a bi-directional driving system is used to drive the microfluid. In such a design, it is not necessary to provide two groups of driving force providers. In addition, the driving force provider is not limited to the electro-osmosis pumps as shown in the embodiment of this invention. In this invention, it is possible to provide a special function in avoiding the adhesion of the blood cell or the protein fibers, when the microfluid is the blood. It is majorly because any inlet blood is at the negative electrodes of the electro-hydrodynamic pump where electrical rejection is generated to avoid the blood cells from being contacted with the electrodes. Although the outlet blood is at the side of the positive electrode of the electro-osmosis pump, the substantial current rejection is strong enough to push away the blood cells. Although this invention is suited in cultivating cells in blood, it is understood that it is suited in any microfluid. The microfluid is not limited to blood or human blood. The organisms to be cultivated are not limited to animal cells. Other micro organisms such as hepatocytes, endocrine cells, bacteria, tissue . . . etc. may be cultivated in the cultivation device of this invention. As the present invention has been shown and described with reference to preferred embodiments thereof, those skilled in the art will recognize that the above and other changes may be made therein without departing form the spirit and scope of the invention.