refer to fig1 for a flowchart of a method for assembling a 3d microelectrode structure according to the present invention . the method for assembling a 3d microelectrode structure of the present invention comprises the steps of : a . fabricating 2d microelectrode arrays ; b . stacking and neatly arranging the 2d microelectrode arrays at predetermined positions to form a 3d microelectrode array ; c . assembling the 3d microelectrode array to a carrier chip to form a 3d microelectrode structure . in step a , a 2d microelectrode array 10 is fabricated . refer to fig2 for an embodiment of a 2d microelectrode array 10 according to the present invention . the 2d microelectrode array 10 comprises a base 11 , a plurality of probes 12 connected to the base 11 , a plurality of alignment members 13 connected to the base 11 , and a plurality of positioning members 14 connected to the base 11 . the probes 12 and the alignment members 13 are respectively located at different sides of the base 11 . each alignment member 13 has an exposed electric - connection member 130 . each probe 12 has at least one electrode 120 . the electrodes 120 are respectively electrically connected to the corresponding electric - connection member 130 via wires 15 . the wires 15 are electrically insulated to each other . the wires 15 are wrapped inside the probes 12 and the base 11 lest the wires 15 electrical short to the body fluid . in this embodiment , the alignment members 13 and the positioning members 14 are located at the same side of the base 11 . considering the biocompatibility with organisms , the 2d microelectrode array 10 , especially the base 11 and probe 12 , are made of a high biocompatibility material , such as a glass , pdms ( polydimethylsiloxane ), pi ( polyimide ), or a thick su - 8 photoresist . considering the influence of material strength on the insertion depth , the 2d microelectrode array 10 is made of a glass and fabricated with a glass reflow technology in one embodiment . however , the present invention is not limited by this embodiment . as the glass reflow technology is a prior art , it will not repeat herein . for the details of the glass reflow technology , please refer to an u . s . pat . no . 7 , 259 , 080 “ glass - type planar substrate , use thereof , and method for the production thereof ”, and an u . s . pat . no . 6 , 951 , 119 “ method for producing micromechanical and micro - optic components consisting of glass - type materials ”. refer to fig3 a - 3d for diagrams schematically showing the process of fabricating a 2d microelectrode array 10 according to the present invention . as shown in fig3 a , a master mold 200 is formed on a silicon wafer 100 firstly ; then , molten glass is cast into the master mold 200 via a glass reflow technology ; then , the undesired portions are removed via lapping ; thus is formed the rough structure of the base 11 plus the probes 12 . next , as shown in fig3 b , a metal film 300 and an insulating film 400 are deposited to define the electrodes 120 , the wires 15 and the electric - connection members 130 of the 2d microelectrode array 10 . the insulating film 400 is made of an insulating material , such as silicon dioxide , silicon nitride , or parylene . next , as shown in fig3 c , the undesired silicon structure is removed by etching , and the thickness of the silicon structure of the alignment members 13 is defined at the same time . next , as shown in fig3 d , an adhesive layer 500 is deposited on the predetermined position . the adhesive layer 500 may be made of parylene - c . thus is completed the 2d microelectrode array 10 . refer to fig2 again . in the abovementioned embodiment , the metal film 300 is located on the probe 12 and is exposed from the insulating silicon dioxide film 400 to be defined the electrode 120 ; the metal film 300 , which is exposed from the alignment member 13 , is defined to be the electric - connection member 130 . it should be understood that the process of fabricating a 2d probe 12 array described in the abovementioned embodiments is only an exemplification of the present invention . in practical applications , the electrode 120 , wire 15 , and electric - connection member 130 may be made of different material according to the characteristics and requirements , such as the electrode 120 can be selected from a group consisting of cnt ( carbon nano - tubes ), iridium oxide , platinum , gold , titanium , platinum black , or an electric - conduction polymer pedot ( polyethylenedioxythiophene ). further , the base 11 , probes 12 , alignment members 13 and positioning members 14 mentioned in the embodiments may be fabricated into independent parts or a one - piece component . in step b , the 2d microelectrode arrays 10 are stacked and neatly arranged to form a 3d microelectrode array 30 . refer to fig4 a - 4e for diagrams schematically showing the procedures of step b according to one embodiment of the present invention . in this embodiment , an auxiliary tool 20 is used to arrange the alignment members 13 of the 2d microelectrode arrays 10 neatly at the predetermined positions , whereby the 2d microelectrode arrays 10 are stacked to form a 3d microelectrode array 30 . as shown in fig4 a and 4b , the auxiliary tool 20 has a plurality of slots 21 arranged in parallel . the slots 21 accommodate the alignment members 13 and the positioning members 14 , enable the 2d microelectrode arrays 10 to slide along the direction parallel to the slots 21 , and align the corresponding 2d microelectrode arrays 10 . the width of each slot 21 and the spacing between two adjacent slots 21 are not strictly limited . however , considering the positioning effect , the width of each slot 21 is preferred to be slightly greater than the width of the alignment member 13 . in one embodiment , the sections of the slots 21 are patterned on a wafer , and the sections are etched to form the auxiliary tool 20 . as shown in fig4 c and 4d , a plurality of 2d microelectrode arrays 10 located at the alignment positions of the auxiliary tool 20 is stuck to form a 3d microelectrode array 30 via adhesive layers 22 . as shown in fig4 e , the alignment members 13 are thus arranged to have a predetermined shape . during the assembling , the positioning and securing effect is enhanced via heating and applying pressure to the 3d microelectrode array 30 along the direction to the slots 21 ( indicated by the arrow in fig4 d ). in one embodiment , parylene - c is uniformly coated on the contact faces of the bases 11 of the 2d microelectrode arrays 10 , and then the 2d microelectrode arrays 10 are pressured and heated to a temperature of 260 ° c . for 2 hours , whereby forms the 3d microelectrode array 30 . as shown in fig4 e , the alignment members 13 of different 2d microelectrode arrays 10 are alternately arranged lest interference occurs . however , it should be understood that the present invention does not strictly limit the arrangement of the alignment members 13 of the established 3d microelectrode array 30 . in step c , the 3d microelectrode array 30 is assembled to a carrier chip 40 to form a 3d microelectrode structure 1 . refer to fig5 a and 5b respectively for a diagram schematically showing the appearance of the carrier chip 40 and a diagram schematically showing the procedure of step c . the carrier chip 40 includes a plurality of electric - connection pads 41 and a plurality of slots 42 . the arranged pattern of the electric - connection pads 41 is corresponding to the alignment members 13 of the 3d microelectrode array 30 , whereby each exposed electric - connection member 130 of the alignment member 13 can electrically connect to the corresponding electric - connection pad 41 . the slots 42 accommodate the positioning members 14 to assist in aligning and securing the 3d microelectrode array 30 to the carrier chip 40 . as shown in fig5 b , a conductive paste 43 is used as the adhesive and electric - conduction medium when the electric - connection pads 41 contact the electric - connection members 130 . in assembling , the positioning members 14 of the 3d microelectrode array 30 are inserted into the slots 42 , whereby the alignment members 13 can be aligned to contact the electric - connection pads 41 . the conductive paste 43 is heated and solidified to interconnect the electric - connection pads 41 and the electric - connection members 130 . the conductive paste 43 may be a silver paste . as shown in fig5 c , the 3d microelectrode structure 1 is further integrated with a flexible substrate and an asic to perform nervous system measurement . the alignment of the 2d microelectrode arrays 10 is implemented with the alignment members 13 of the base 11 . different type 2d microelectrode arrays 10 may have different numbers and shapes of probes 12 . however , in the present invention , different type 2d microelectrode arrays 10 can be assembled into corresponding 3d microelectrode arrays 30 with the same auxiliary tool 20 or the same carrier chip 40 , as long as they have the same type of base 11 . thus is increased the design flexibility and expanded the application of the probe 12 . for example , the combinations of the probes 12 having different lengths can be used to measure the physiological signals from different depths of an organism at the same time . further , as the alignment member 13 has a greater bottom area , the electric - connection member 130 can easily conduct the electric - connection pad 41 in step c . thus , the disconnection caused by an alignment error will not occur . it should be understood that the electric - connection member 130 exposed from the alignment member 13 may be a portion of the alignment member 13 or the alignment member 13 itself in fact . in this specification , different terms do not necessarily indicate different entities but may be used to demonstrate different aspects of the same thing . the present invention also proposes a 3d microelectrode structure 1 , which is assembled with the abovementioned method , comprises a carrier chip 40 and a 3d microelectrode array 30 electrically connected to the carrier chip 40 , wherein a plurality of 2d microelectrode arrays 10 is stacked to form the 3d microelectrode array 30 . the material and detailed structure of the 2d microelectrode array 10 is the same as that described above . the 2d microelectrode arrays 10 are stacked to make the bases 11 thereof contact each other and form the 3d microelectrode array 30 . in one embodiment , the probe 12 is made of a glass material and thus has high insertion ability and high biocompatibility . in the present invention , different type 2d microelectrode arrays 10 having different numbers and shapes of probes 12 may adopt the same type of base 11 . therefore , the present invention can easily realize the 3d microelectrode arrays 30 having flexible arrangements and combinations of probes 12 , such as a 3d microelectrode arrays 30 having longer probes 12 for a greater insertion depth . in another embodiment , the probes 12 have several electrodes 120 to measure more nerve cells . the signals of a nervous system are mainly transmitted by neurons . when a neuron is stimulated , special ion channels on the cell membrane is opened . thus , ions , such as potassium ions and sodium ions , flow through cell membrane and result in potential change . when the potential is accumulated over a threshold , an action potential is generated and detected by the probe 12 in the form of voltage . the 3d microelectrode structure 1 of the present invention has succeeded in measuring and recording the action potential of crayfish nerve cord and rat cortices . the snr ( signal - to - noise ratio ) in measuring crayfishes is 32 . 6 db , wherein the snr is defined to be the ratio of the amplitude of the nerve impulse to the root - mean - square value of noise . the embodiments described above are only to exemplify the present invention but not to limit the scope of the present invention . any equivalent modification or variation according to the scope of the present invention is to be also included within the scope of the present invention .