Abstract:
A method for fabricating a plurality of biosensors includes the steps of: providing a base with a surface; forming a carbon nanotube array including a plurality of carbon nanotubes substantially parallels to each other on the surface; forming a plurality of lead pairs on the surface, the plurality of lead pairs divides the plurality of carbon nanotubes into a plurality of first carbon nanotubes and a plurality of second carbon nanotubes; eliminating the plurality of second carbon nanotubes; cutting the plurality of first carbon nanotubes to form a plurality of third carbon nanotubes and a plurality of fourth carbon nanotubes; and fabricating a plurality of receptors to electrically connect the plurality of third carbon nanotubes to the plurality of fourth carbon nanotubes.

Description:
RELATED APPLICATIONS 
       [0001]    This application is a continuation application of U.S. patent application Ser. No. 13/008146, filed Jan. 18, 2011, entitled, “BIOSENSOR, BIOSENSOR PACKAGE STRUCTURE HAVING SAME, AND METHOD FOR FABRICATING SAME,” which claims all benefits accruing under 35 U.S.C. §119 from China Patent Application No. 201010521439.0, filed on Oct. 27, 2010 in the China Intellectual Property Office. 
     
    
     BACKGROUND 
       [0002]    1. Technical Field 
         [0003]    The present disclosure relates to a biosensor with electrodes comprising a plurality of carbon nanotubes, a biosensor package structure having the same, and a method for fabricating the same. 
         [0004]    2. Description of Related Art 
         [0005]    In general, a biosensor is a device that uses a specific biological element or a physical element similar to the biological element to get information from a measured object. The detected information is usually transduced by the biosensor into recognizable signals such as colors, fluorescence, or electrical signals. With technical advances in modem science, a biosensor is one of the devices that have developed rapidly. 
         [0006]    A biosensor is composed of a receptor which reacts with a measured object to be detected, and electrodes which transmit current variation generated by the reaction between the receptor and the measured object. Examples of the receptor include an enzyme, antibody, antigen, membrane, receptor, cell, tissue, and deoxyribonucleic acid (DNA), which selectively reacts with the measured object. The electrodes are usually metal electrodes. 
         [0007]    However, a width of each of the metal electrodes in the above-described biosensor is in a range from several micrometers (um) to dozens of micrometers. Thus, an amount of electrodes in a unit area of the biosensor is too few to influence accuracy and sensitivity of the same. Furthermore, the metal electrodes with poor inoxidability will shorten a lifetime of the biosensor. 
         [0008]    Thus, there remains a need for providing a new biosensor which has greater accuracy, sensitivity, and a longer lifetime. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    Many aspects of the disclosure can be better understood with reference to the drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present disclosure. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the views. 
           [0010]      FIGS. 1 ,  2 , and  3  are schematic views of embodiments of a biosensor. 
           [0011]      FIG. 4  is a schematic view of an embodiment of a biosensor package structure. 
           [0012]      FIGS. 5 ,  6 ,  7 ,  8 , and  9  show different schematic views of processes to manufacture a plurality of biosensors. 
       
    
    
     DETAILED DESCRIPTION 
       [0013]    The disclosure is illustrated by way of example and not by way of limitation in the figures of the accompanying drawings in which like references indicate similar elements. It should be noted that references to “an” or “one” embodiment in this disclosure are not necessarily to the same embodiment, and such references mean at least one. 
         [0014]    According to one embodiment, a biosensor  120  as illustrated in  FIG. 1  comprises a base  180  with a surface, two electrodes  1210  and  1220 , and a receptor  1230 . The two electrodes  1210  and  1220  are illustrated as a first electrode  1210  and a second electrode  1220  for exemplification and should not be treated as a limitation. The first electrode  1210 , the second electrode  1220 , and the receptor  1230  are located on the surface of the base  180  with an interval. 
         [0015]    The first electrode  1210  comprises a first lead  1212  and a plurality of first carbon nanotubes  1214 . The first carbon nanotubes  1214  are substantially parallel to each other, and comprise a first probe  1216 . The first lead  1212  is electrically connected to one side of each of the first carbon nanotubes  1214  and an external circuit (not shown). 
         [0016]    Similarly, the second electrode  1220  comprises a second lead  1222  and a plurality of second carbon nanotubes  1224 . The second carbon nanotubes  1224  are substantially parallel to each other, and comprise a second probe  1226 . The second lead  1222  is electrically connected to one side of each of the second carbon nanotubes  1224  and an external circuit (not shown). 
         [0017]    The first carbon nanotubes  1214  and the second carbon nanotubes  1224  can be single-walled carbon nanotubes, double-walled carbon nanotubes, multi-walled carbon nanotubes, or combinations thereof. The diameter of the single-walled carbon nanotubes can be in the range from about 0.5 nanometers (nm) to about 50 nm. The diameter of the double-walled carbon nanotubes can be in the range from about  1  nm to about 50 nm. The diameter of the multi-walled carbon nanotubes can be in the range from about 1.5 nm to about 50 nm. In one embodiment, the length of the first carbon nanotubes  1214  and the second carbon nanotubes  1224  can be in a range from about  10  micrometers (um) to about 50 um. 
         [0018]    More specifically, the first carbon nanotubes  1214  respectively correspond to the second carbon nanotubes  1224 . Thus, the first probe  1216  of each of the first carbon nanotubes  1214  corresponds to the second probe  1226  of each of the second carbon nanotubes  1224 . A distance between each two first carbon nanotubes  1214  is in a range from about 5 um to about 10 um. Similarly, a distance between each two second carbon nanotubes  1224  is in a range from about 5 um to about 10 um. A distance between the first probe  1216  of each of the first carbon nanotubes  1214  and the second probe  1226  of each of the second carbon nanotubes  1224  is equal to or less than 10 um. Furthermore, as shown in  FIG. 1 , an extended direction of each of the first carbon nanotubes  1214  is substantially parallel to an extended direction of each of the second carbon nanotubes  1224 . 
         [0019]    The first lead  1212  and the second lead  1222  can be conductive thick liquid, metal, carbon nanotubes, indium tin oxide (ITO), or any combination thereof. In one embodiment, the first lead  1212  and the second lead  1222  are made by printing or plating the conductive thick liquid. The conductive thick liquid comprises powdered metal, powdered glass with a low fusion point, and binder. The powdered metal is powdered silver. The binder is terpineol or ethyl cellulose. A weight percentage of the powdered metal is in a range from about 50% to about 90%. A weight percentage of the powdered glass with a low fusion point is in a range from about 2% to about 10%. A weight percentage of the binder is in a range from about 8% to about 40%. 
         [0020]    The receptor  1230  comprises a plurality of carriers  1232  and a plurality of sensing materials  1234 . The sensing materials  1234  are embedded in each of the carriers  1232 . The first probe  1216  of each of the first carbon nanotubes  1214  and the second probe  1226  of each of the second carbon nanotubes  1224  are covered by the receptor  1230 , such that the first electrode  1210  and the second electrode  1220  are electrically connected to each other. More specifically, the carriers  1232  define a plurality of conductive circuits, between the first carbon nanotubes  1214  of the first electrode  1210  and the second carbon nanotubes  1224  of the second electrode  1220 , to electrically connect the sensing materials  1234 . 
         [0021]    The carriers  1232  can be carbon nanotubes, carbon fibers, amorphous carbon, graphite, or any combination thereof. In one embodiment, the carriers  1232  are carbon nanotubes with a plurality of functional groups. The functional groups can be carboxyl (—COOH) groups, hydroxyl (—OH) groups, aldehyde (—CHO) groups, amino (—NH2) groups, or any combination thereof. 
         [0022]    In testing, the sensing materials  1234  embedded in the carriers  1232  react to a measured object such that current of the biosensor  120  is varied. The current variation of the biosensor  120  is transmitted by the first carbon nanotubes  1214  and the first lead  1212 . Alternatively, the current variation of the biosensor  120  is transmitted by the second carbon nanotubes  1224  and the second lead  1222 . The sensing materials  1234  can be antibodies, antigens, DNA, or any combination thereof. In one embodiment, the sensing materials  1234  are antibodies. 
         [0023]    According to another embodiment, a biosensor  120  as illustrated in  FIG. 2  comprises a base  180  with a surface, a first lead  1212 , a plurality of first carbon nanotubes  1214 , a second lead  1222 , and a plurality of second carbon nanotubes  1224 . Each of the first carbon nanotubes  1214  comprises a first probe  1216 , and each of the second carbon nanotubes  1224  comprises a second probe  1226 . Furthermore, as shown in  FIG. 2 , the first carbon nanotubes  1214  substantially parallel to each other and the second carbon nanotubes  1224  substantially parallel to each other form a specific angle. 
         [0024]    According to still another embodiment, a biosensor  120  as illustrated in  FIG. 3  comprises a base  180  with a surface, a first lead  1212 , a plurality of first carbon nanotubes  1214 , a second lead  1222 , and a plurality of second carbon nanotubes  1224 . 
         [0025]    Each of the first carbon nanotubes  1214  comprises a first probe  1216 , and each of the second carbon nanotubes  1224  comprises a second probe  1226 . Furthermore, as shown in  FIG. 3 , an extended direction of each of the first carbon nanotubes  1214  is substantially perpendicular to an extended direction of each of the second carbon nanotubes  1224 . 
         [0026]    According to an embodiment, a biosensor package structure  100  as illustrated in  FIG. 4  comprises a base  180  with a surface, a cover box  110 , and a plurality of biosensors  120 . The base  180  and the cover box  110  are plastered to each other to define a cavity  1102 . 
         [0027]    The base  180  which comprises conductive wires  150  can be a hard base or a flexible base. The hard base can be a ceramic base, a glass base, a quartziferous base, a siliceous base, an oxidative siliceous base, a diamond base, an alumina base, or any combination thereof. The flexible base can be a macromolecule base made by polydimethylsiloxane (PDMS), polycarbonate (PC), polymethyl methacrylate (PMMA), polyethylene (PE), polyimide (PI), polyethylene terephthalate (PET), polyether sulphone (PES), cellulose resin, polyvinylchloride (PVC), benzocyclobutene (BCB), acrylic resin, or any combination thereof. The base  180  comprises a siliceous slice  1802  with a surface and a silica layer  1804  formed on the surface of the siliceous slice  1802 . In one embodiment, a thickness of the siliceous slice  1802  is in a range from about 0.5 millimeter (mm) to about  2  mm, and a thickness of the silica layer  1804  is in a range from about 100 um to about 500 um. 
         [0028]    The cover box  110  comprises an input passage  1104  and an output passage  1106 . The input passage  1104  is disposed in one side of the cover box  110 , and the output passage  1106  is disposed in an opposite side of the same. In the embodiment, the cover box  110  is a poly dimethyl siloxane (PDMS) box. Diameters of the input passage  1104  and the output passage  1106  is in a range from about 200 um to about 400 um. The cavity  1102  is defined as a cuboid, a length of the cavity  1102  is in a range from about 5 mm to about 10 mm, a width of the same is in a range from about 0.2 mm to about 1 mm, and a height of the same is in a range from about 50 um to about 100 um. 
         [0029]    The biosensors  120  are located on the surface of the base  180  side by side. The first electrode  1210  and the second electrode  1220  of each of the biosensors  120  are connected to pins  160  by the conductive wires  150 . Thus, the biosensors  120  are electrically connected to the external circuit via the pins  160 . 
         [0030]    Accordingly, when the measured object is delivered to the cavity  1102  by the input passage  1104 , and withdrawn from the cavity  1102  by the output passage  1106 , the measured object will pass through the biosensors  120 . Thus, the biosensors  120  react to the measured object such that current of each of the biosensors  120  is varied. Afterward, the current variation of each of the biosensors  120  is transmitted to the external circuit by the conductive wires  150  and the pins  160 . Finally, the external circuit can get information from the measured object. 
         [0031]    According to an embodiment, a method for fabricating a plurality of biosensors is illustrated in following steps. For exemplary purpose, the embodiment is adapted for fabricating the biosensors  120  of  FIG. 1 . 
         [0032]    Referring to  FIG. 5 , in step one, a base  180  with a surface is provided, and a carbon nanotube array  190  is formed on the surface of the base  180 . The carbon nanotube array  190  comprises a plurality of carbon nanotubes substantially parallel to each other. 
         [0033]    Referring to  FIG. 6 , in step two, a plurality of first leads  1212  and a plurality of second leads  1222  are formed by printing or plating conductive thick liquid on the surface of the base  180 . Each of the first leads  1212  corresponds to each of the second leads  1222 , and are electrically connected to each other by at least one of the carbon nanotubes of the carbon nanotube array  190 . 
         [0034]    Referring to  FIG. 7 , in step three, a part of the carbon nanotubes of the carbon nanotube array  190  is eliminated. Thus, the carbon nanotubes between each of the first leads  1212  and each of the second leads  1222  remain on the surface of the base  180 . 
         [0035]    Referring to  FIG. 8 , in step four, the carbon nanotubes between each of the first leads  1212  and each of the second leads  1222  are cut to form a plurality of first carbon nanotubes  1214  and a plurality of second carbon nanotubes  1224 . Each of the first carbon nanotubes  1214  corresponds to each of the second carbon nanotubes  1224 . 
         [0036]    Referring to  FIG. 9 , in step five, receptors  1230  are fabricated between each of the first leads  1212  and each of the second leads  1222 . Thus, the first carbon nanotubes  1214  and the second carbon nanotubes  1224  between each of the first leads  1212  and each of the second leads  1222  are electrically connected to each other by one of the receptors  1230 . 
         [0037]    Accordingly, the present disclosure is capable of transmitting current variation of a biosensor via electrodes with carbon nanotubes. In addition, a width each of the electrodes can be decreased without influencing the accuracy and sensitivity of the biosensor. Thus, the biosensor can be easily manufactured with greater accuracy, sensitivity, and a longer lifetime. 
         [0038]    It is to be understood that the above-described embodiments are intended to illustrate rather than limit the disclosure. Any elements described in accordance with any embodiments is understood that they can be used in addition or substituted in other embodiments. Embodiments can also be used together. Variations may be made to the embodiments without departing from the spirit of the disclosure. The above-described embodiments illustrate the scope of the disclosure but do not restrict the scope of the disclosure.