Abstract:
The present disclosure relates to peripheral nerve interface system and method for prosthetic hand control, which may measure, analyze and control efferent motor nerve signals and afferent sensory nerve signals by regenerating a peripheral nerve and control an artificial prosthetic hand by means of the measurement, analysis and control of the signals. For this, the peripheral nerve interface system according to an embodiment of the present disclosure includes: a nerve conduit connected to a terminal of a damaged peripheral nerve at a cut body portion; a prosthesis for substituting for the cut body portion; and a peripheral nerve interface unit electrically connected to the nerve conduit and the prosthesis to restore a function of the damaged peripheral nerve and control operations of the prosthesis by transmitting and receiving signals of the damaged peripheral nerve.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to Korean Patent Application No. 10-2012-0028346, filed on Mar. 20, 2012, and all the benefits accruing therefrom under 35 U.S.C. §119, the contents of which in its entirety are herein incorporated by reference. 
     BACKGROUND 
     1. Field 
     The present disclosure relates to peripheral nerve interface system and method for prosthetic hand control, which may measure, analyze and control efferent motor nerve signals and afferent sensory nerve signals by regenerating a peripheral nerve and control an artificial prosthetic hand by means of the measurement, analysis and control of the signals. 
     2. Description of the Related Art 
     If a nerve is damaged, for example if a nerve is cut, stimuli generated in or out of a living body are not normally transferred, and so a seriously bad influence is exerted to an organism. The cutting may occur due to diseases such as arteriosclerosis, diabetes and Buerger disease, injuries caused by car accidents or industrial accidents, infections, tumors, congenital deformities or the like. The number of disabled persons suffering from congenital or acquired deformities is increasing every year, and the rehabilitation and return to the normal social life for disabled persons suffering from cutting become a great issue. 
     Most of disabled persons suffering from cutting rehabilitate by wearing a prosthetic hand, a prosthetic leg or an assist device and training. If such rehabilitating tools are used, a user may not easily feel a touching sense or conduct a complicated work such as writing. In addition, if a patient suffers from serious cutting, wearing and controlling such an assist device is substantially impossible. 
     Existing artificial prosthetic hand or prosthetic foot determines the intent of a behavior by means of body power or surface electromyogram but is disregarded by patients due to low recognition rate and malfunctions. In order to solve such problems, a technique for moving artificial prosthetic hand and foot according to the intention of a user is demanded. In other words, as one of methods using nerves remaining in a cut portion, a nerve control technique and a nerve feedback technique where a sensor is attached to artificial prosthetic hand and foot to feed sense information to the nerves are demanded. 
     In relation to existing nerve signal detection and stimulation, techniques such as a depth type, a planar type, a sieve type and a cuff type are being studied, but these techniques have limits as follows. 
     The planar type (which is also called Microelectrode Array (MEA)) is directed to measuring a nerve signal by means of nerve cell cultivation. However, since the planar type is generally utilized for studying a method for analyzing signals of a nerve system or a method for inputting information to a nerve system, it is not suitable to apply the planar type to a technique of connecting a nerve system and an artificial device. 
     The depth type represents a method of directly inserting an electrode into a nerve tissue and using the electrode. The electrode collects electric signals from surrounding nerves. However, an insertion-type electrode may cause necrosis or accumulations of surrounding cells due to a long time use, which may prevent active signals of nerves from being stably measured. In other words, due to the feature of nerves which are composed of several bundle-type efferent axons, there is a limit in distinguishing signals accurately. 
     The sieve type disclosed in U.S. Pat. No. 6,908,470 is called a nerve-regenerating electrode. The sieve type uses regenerating ability of nerves, where a sieve-shaped electrode is placed between cut nerves so that the efferent axons of the nerve cells are regenerated while passing between the sieve-shaped electrodes. By doing so, a nerve signal may be measured. However, the sieve electrode may be used only when being located between cut nerves, namely only when nerves are alive at both terminals, and so its application scope is limited. 
     The cuff type is directed to measuring a nerve signal by surrounding nerves directly. Since the cuff type measures a nerve signal from an outside of nerves surrounded by an insulator, it is difficult to measure an accurate signal and separate afferent and efferent signals. 
     Therefore, the existing methods described above have limits in detecting nerve signals of cut peripheral nerves composed of bundle-type efferent axons and freely controlling a prosthetic hand through stimulation. 
     RELATED LITERATURES 
     Patent Literature 
     
         
         U.S. Pat. No. 6,908,470 
       
    
     SUMMARY 
     The present disclosure is directed to making it possible to regenerate damaged peripheral nerves of a patient suffering from cutting and selectively detect, analyze, transfer and stimulate nerve signals. In addition, the present disclosure is directed to providing peripheral nerve interface system and method which controls a prosthetic hand accordingly so a disabled person suffering from cutting may undergo rehabilitation. 
     In one aspect, there is provided a peripheral nerve interface system, which includes: a nerve conduit connected to a terminal of a damaged peripheral nerve at a cut body portion; a prosthesis for substituting for the cut body portion; and a peripheral nerve interface unit electrically connected to the nerve conduit and the prosthesis to restore a function of the damaged peripheral nerve and control operations of the prosthesis by transmitting and receiving signals of the damaged peripheral nerve. 
     The nerve conduit may include: a support connected to the terminal of the damaged peripheral nerve; a channel formed in a body of the support and having a cavity shape; an electrode layer formed along an inner wall of the channel; and an external electrode electrically connected to the electrode layer, wherein a nerve cell may grow along the channel at the terminal of the damaged peripheral nerve, the nerve cell having grown along the channel may be electrically connected to the electrode layer, and a plurality of channels may be formed at the support. 
     The peripheral nerve interface unit may include: an internal module implanted into the damaged body portion and electrically connected to the nerve conduit; and an external module positioned out of the damaged body portion and electrically connected to the prosthesis, wherein the internal module and the external module may transmit and receive nerve signals to/from each other in a wireless communication manner. 
     The internal module may include: a first amplifying unit for amplifying the signal of the damaged peripheral nerve received through the nerve conduit; a first AD converter for converting the signal amplified by the first amplifying unit into a digital signal; a first digital signal processing unit for receiving and analyzing the digital signal converted by the first AD converter and transmitting the digital signal to the external module in a wireless communication manner, or receiving and analyzing the digital signal received from the external module and transmitting the digital signal to the grown nerve cell through the channel; a DA converter for converting the digital signal received by the first digital signal processing unit into an analog signal; a stimulating unit for transferring an electric stimulation signal to the grown nerve cell along the plurality of channels by using the analog signal converted by the DA converter; a multiplexer for electrically matching a plurality of nerve cells having grown along the plurality of channels according to an instruction of the first digital signal processing unit with the first amplifying unit and the stimulating unit; and a first communication unit for transmitting and receiving signals to/from the external module in a wireless communication manner. 
     The internal module may further include: a first battery unit for supplying power to the internal module; and a wireless power receiving unit for receiving power from the external module in a wireless manner and transferring the power to the first battery unit. 
     The peripheral nerve interface system may further include a nerve regenerating electrode connected to the damaged peripheral nerve, wherein the stimulating unit may transfer a nerve generating stimulation signal to the nerve regenerating electrode. 
     The first digital signal processing unit may adopt a multilayer perceptron algorithm 
     The external module may include: a second communication unit for transmitting and receiving a signal to/from the internal module in a wireless communication manner; a second AD converter for converting an analog signal received by a sensor installed at the prosthesis into a digital signal; a second digital signal processing unit for analyzing and processing the signal of the peripheral nerve received by the second communication unit and transmitting the signal to the internal module through the second communication unit based on the signal received by the second AD converter; an embedded controller for controlling operations of the prosthesis based on the signal processed by the second digital signal processing unit; and a second amplifying unit for amplifying a control signal of the embedded controller and transferring the amplified control signal to the prosthesis. 
     The external module may include: a second battery unit for supplying power to the external module; and a wireless power transmitting unit for receiving power from the second battery unit and transmitting the power to the internal module in a wireless manner. 
     The prosthesis may include at least one sensor for detecting a sensory signal. 
     In another aspect, there is also provided a peripheral nerve interface method, which include: regenerating a nerve cell at a terminal of a damaged peripheral nerve of a cut body portion by using a nerve conduit; detecting an efferent motor nerve signal by using an internal module implanted in the cut body portion and electrically connected to the nerve conduit; transmitting the efferent motor nerve signal to an external module located out of the cut body portion; and controlling an operation of a prosthesis which substitutes for the cut body portion by using the external module. 
     The peripheral nerve interface method according to an embodiment of the present disclosure may further include: detecting, by a sensor installed at the prosthesis, an afferent sensory signal; analyzing, by the external module, the detected afferent sensory signal; receiving, by the internal module, the afferent sensory signal from the external module; and generating, by the internal module, an electric stimulation signal corresponding to the afferent sensory signal and transferring the electric stimulation signal through the nerve conduit to the nerve cell at the terminal of the peripheral nerve. 
     The peripheral nerve interface method according to an embodiment of the present disclosure may further include transferring, by the internal module, a nerve generating stimulation signal to a nerve regenerating electrode connected to the damaged peripheral nerve. 
     In the peripheral nerve interface method according to an embodiment of the present disclosure, the nerve conduit may include a porous polymer electrode, and the method may further: include selectively detecting the efferent motor nerve signal or the afferent sensory nerve signal by using the porous polymer electrode; and selectively transferring an electric stimulation signal to the nerve cell at the terminal of the damaged peripheral nerve, which may be performed by using a multilayer perceptron algorithm. 
     The peripheral nerve interface system and method according to the present disclosure may effectively regenerate peripheral nerves at a cutting portion by using a nerve conduit having a porous polymer electrode, a peripheral nerve interface unit and a prosthesis, and may effectively control a prosthesis such as a prosthetic hand by transmitting or receiving efferent motor nerve signals and afferent sensory nerve signals. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other aspects, features and advantages of the disclosed exemplary embodiments will be more apparent from the following detailed description taken in conjunction with the accompanying drawings in which: 
         FIG. 1  is a schematic diagram showing a peripheral nerve interface system according to an embodiment of the present disclosure; 
         FIG. 2  is a perspective view showing a nerve conduit applied to the peripheral nerve interface system according to an embodiment of the present disclosure; 
         FIG. 3  is a sectioned perspective view showing the nerve conduit of  FIG. 2 ; 
         FIG. 4  is a cross-sectional view showing a part of the nerve conduit of  FIG. 3 ; 
         FIG. 5  is a detailed diagram showing a peripheral nerve interface unit applied to the peripheral nerve interface system according to an embodiment of the present disclosure; 
         FIG. 6  is a conceptual diagram for illustrating a signal transmission operation of the peripheral nerve interface system according to an embodiment of the present disclosure; and 
         FIG. 7  is a diagram showing a prosthesis applied to the peripheral nerve interface system according to an embodiment of the present disclosure. 
     
    
    
     
       
         
               
             
               
               
               
             
           
               
                   
               
               
                 Detailed Description of Main Elements 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 100: nerve conduit 
                 200: peripheral nerve interface unit 
               
               
                   
                 220: internal module 
                 240: external module 
               
               
                   
                 300: prosthesis 
               
               
                   
               
             
          
         
       
     
     DETAILED DESCRIPTION 
     Exemplary embodiments now will be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments are shown. The present disclosure may, however, be embodied in many different forms and should not be construed as limited to the exemplary embodiments set forth therein. Rather, these exemplary embodiments are provided so that the present disclosure will be thorough and complete, and will fully convey the scope of the present disclosure to those skilled in the art. 
       FIG. 1  is a schematic diagram showing a peripheral nerve interface system according to an embodiment of the present disclosure. 
     Referring to  FIG. 1 , the peripheral nerve interface system according to an embodiment of the present disclosure includes a nerve conduit  100 , a peripheral nerve interface unit  200  and a prosthesis  300 . 
     The nerve conduit  100  is electrically connected to a peripheral nerve  10  of a cut body portion to detect a nerve signal or transfer an electric stimulation signal. In detail, a plurality of channels  120  having a cavity shape are formed in the nerve conduit  100 , and an electrode layer  121  is formed in the channel  120 . The electrode layer  121  is electrically connected to an efferent axon  12  which is regenerated at a terminal of the peripheral nerve. 
     In particular, since the nerve conduit  100  has the plurality of channels  120 , the nerve conduit  100  may connect a plurality of nerve cells of the regenerated efferent axon  12  to each electrode so that an efferent motor nerve signal is transferred to an internal module  220 , described later, through a second connection unit  142  made of wire or the like. In addition, the nerve conduit  100  may receive a stimulation signal or a nerve generating stimulation signal from an internal module  220  of the peripheral nerve interface unit  200 . 
     The nerve cell at the terminal of the peripheral nerve  10  may be regenerated and electrically connected to the nerve conduit  100 , and a ring-shaped nerve regenerating electrode  7  is coupled to the peripheral nerve  10 . The nerve regenerating electrode  7  plays a role of transferring a nerve-regenerating electric stimulation signal from the internal module  220  to the peripheral nerve  10 . 
     Detailed configuration and operations of the nerve conduit  100  according to the present disclosure, which adopts a porous polymer electrode in order to selectively detect nerve signals of a plurality of nerve cells will be described later with reference to  FIGS. 2 to 4 . 
     The peripheral nerve interface unit  200  includes an internal module  220  and an external module  240  and the peripheral nerve interface unit  200  transmits or receives a nerve signal or an electric stimulation signal between the peripheral nerve  10  of the cut body portion and the prosthesis  300  connected to the cut body portion. 
     The internal module  220  is implanted in a body of a human or animal and electrically connected to the nerve conduit  100 . Referring to  FIG. 1 , the internal module  220  is implanted in a skin  5  and includes a first digital signal processing unit  221 , a wireless power receiving unit  223 , a first communication unit  225 , a first amplifying unit  226  and a stimulating unit  227 . 
     The first amplifying unit  226  receives and amplifies an efferent motor nerve signal transferred from the nerve conduit  100 . The first digital signal processing unit  221  analyzes the amplified efferent motor nerve signal and transmits the analyzed amplified efferent motor nerve signal through the first communication unit  225  to an external module  240 , described later. In addition, the stimulating unit  227  plays a role of transferring the electric stimulation signal to the nerve conduit  100  according to an instruction of the first digital signal processing unit  221 . The wireless power receiving unit  223  plays a role of receiving power from the external module  240  in a wireless manner and supplying the power to the internal module  220 . 
     The external module  240  is located out of the body, namely the skin  5 , and includes an embedded controller  241 , a wireless power transmitting unit  243  and a second communication unit  245 . Referring to  FIG. 1 , the external module  240  transmits or receives signals to/from the first communication unit  225  of the internal module  220  through the second communication unit  245 . The wireless power transmitting unit  243  supplies power to the wireless power receiving unit  223  of the internal module  220  in a wireless manner. The embedded controller  241  generates an actuator control signal according to the efferent motor nerve signal received from the internal module  220  and controls a joint of the prosthesis  300 . 
     The prosthesis  300  is an artificial assisting tool which assists the cut body portion of a patient and may be a robot module such as a prosthetic hand and a prosthetic foot. At least one sensor  310  for sensing sensory signals of a body may be installed at the prosthesis  300 , and at least one sensor  310  is connected to the external module  240  through the third connection unit  330 . 
     General operations of the peripheral nerve interface system according to the embodiment of the present disclosure will be described below. 
     First, the efferent axon  12  of the peripheral nerve  10  grows through the channel  120  and is connected to the electrode layer  121 . The electrode layer  121  is connected to the internal module  220  through the second connection unit  142 , and the efferent motor nerve signal is transferred to the first amplifying unit  226  and then amplified. The amplified signal is transferred to the external module  240  through the first digital signal processing unit  221  and the first communication unit  225 . 
     The second communication unit  245  of the external module  240  receives the efferent motor nerve signal and transmits the efferent motor nerve signal to the embedded controller  241 . The embedded controller  241  generates an actuator control signal corresponding to the efferent motor nerve signal to control a joint operation of the prosthesis  300 . 
     In addition, at least one sensor  310  capable of sensing sensory signals such as a touch signal is installed at the prosthesis  300 . The sensor  310  may be configured with various sensors such as a pressure sensor and a temperature sensor. If the sensor  310  senses a sensory signal, the sensory signal is transferred through the third connection unit  330  to the external module  240 , and the external module  240  transfers the sensory signal through the second communication unit  245  to the internal module  220 . The first digital signal processing unit  221  of the internal module  220  which has received the sensory signal transmits an electric stimulation signal corresponding to the sensory signal through the stimulating unit  227  and the second connection unit  142  to the nerve conduit  100 . 
       FIG. 2  is a perspective view showing a nerve conduit applied to the peripheral nerve interface system according to an embodiment of the present disclosure. 
     Referring to  FIG. 2 , the nerve conduit  100  includes a cylindrical support  110  and a plurality of channels  120  formed in a body of the support  110  and having a cavity shape. As described later, an electrode layer  121  (see  FIGS. 3 and 4 ) is formed at each channel  120  along the inner wall thereof. 
     The support  110  has a cylindrical body and is connected to a terminal of a cut nerve. The support  110  is made of polyurethane and is formed with a plurality of fibers. The material of the support  110  is not limited to the above, and a bio-friendly material capable of forming a certain shape with a predetermined strength may be adopted as the support  110  of this embodiment. 
     The plurality of channels  120  are formed in the body of the support  110  in the length direction of the support  110 . For convenience, the channels  120  are depicted with dotted lines. 
     An external electrode  130  is formed at an entrance of each of the plurality of channels  120  (namely, at the upper surface of the support  110 ). The external electrode  130  is electrically connected to the electrode layer  121  as described later, and is also electrically connected to a connection electrode  140  formed at the upper surface of the support  110 . 
     The connection electrode  140  includes a ring-shaped first connection unit  141  formed along the upper circumference of the support  110  and a second connection unit  142  electrically connected to the first connection unit  141 . 
     As shown in  FIG. 2 , the first connection unit  141  is electrically connected to the external electrodes  130  connected to each channel  120 , and the second connection unit  142  is electrically connected to the internal module  220 . 
       FIG. 3  is a sectioned perspective view showing the nerve conduit of  FIG. 2 . In  FIG. 3 , the nerve conduit  100  is depicted as being cut by half in the length direction thereof. 
     As shown in  FIG. 3 , an electrode layer  121  is formed at the inner wall of the channel  120 . According to this embodiment, the electrode layer  121  is formed with a plurality of nano fibers extending toward the center of the channel  120 . 
     For convenience, it could be understood that the diameter of nano fibers and the distance between nano fibers are exaggerated in  FIG. 3 . The nano fibers may be formed more minutely and more densely depending on the manufacturing process condition. 
     In one embodiment, the nano fiber may be GaZnO obtained by doping zinc oxide (ZnO) with gallium (Ga), whose electric properties may be controlled. GaZnO is a ceramic material with excellent conductivity, and, when being used as an electrode, GaZnO has excellent biocompatibility due to low toxicity, different from general metals. 
     In order to distribute nano fibers in the channel  120  uniformly and use the distributed nano fiber layer as the electrode layer  121 , this embodiment uses a so-called sol-gel process. The sol-gel process is used so that the nano fibers grow uniformly at the inner surface of the common channel  120 , and an electric network is formed among the nano fibers so that the inside of the channel  120  has conductivity due to the nano fibers. 
     The sol-gel process is well known in the art and thus not described in detail here. 
     The external electrode  130  is formed at the entrance of each channel  120  and is electrically connected to the electrode layer  121 . The external electrode  130  includes a first electrode unit  131  formed with a ring shape along the circumference of the entrance of the channel  120  and a second electrode unit  132  extending to be electrically connected to the first electrode unit  131 . 
     The first electrode unit  131  is connected to a part of the electrode layer  121  exposed to the upper surface of the support  110  to make an electric connection to electrode layer  121 , and the second electrode unit  132  is electrically connected to the first connection unit  141  of the connection electrode  140 . 
     In this embodiment, the electrode layer  121  formed at the inner surface of each channel  120  and the external electrode  130  electrically connected thereto have the same configuration. 
     Hereinafter, the channel  120  and relevant configurations will be described in detail with reference to  FIG. 4 . 
       FIG. 4  is a cross-sectional view showing a part of the nerve conduit of  FIG. 3 .  FIG. 4  shows a single channel  120 , and other channels have the same configuration. 
     As shown in  FIG. 4 , a nerve cell (namely, the efferent axon  12 ) grows into the channel  120  from the terminal of a cut nerve. Even though  FIG. 4  shows only one strand of the efferent axon  12 , multiple strands of the nerve cells may grow (be regenerated) in the channel  120 . The method for regenerating nerve cells is already well know in the art and thus is not described in detail here since the method is not included in the scope of the present disclosure. 
     The efferent axon  12  grows into the channel  120  along the inner wall of the channel  120  by using nano fibers as a support material. Since nano fibers are used as the support material, the efferent axon  12  is firmly fixed in the channel  120 . 
     As described above, since the nano fibers form the electrode layer  121  at the inner wall of the channel  120 , the efferent axon  12  is naturally electrically connected to the electrode layer  121 . 
     Therefore, the efferent nerve signal transferred from the efferent axon  12  to the electrode layer  121  may be detected by the external electrode  130  and transferred to the outside through the connection electrode  140 . In addition, the external electric signal transferred through the connection electrode  140  may be transferred to the efferent axon  12  through the external electrode  130  and the electrode layer  121 . 
     According to this embodiment, a plurality of channels  120  may be formed in the support  110  simultaneously. In particular, since the nerve is composed of a plurality of nerve cell bundles which are respectively connected to different organs in general cases, by forming a plurality of channels  120  in the support  110  and allowing nerve cell bundles to selectively grow in each channel  120 , the process of classifying and transferring nerve signals may be more easily performed. 
     The support  110  with the plurality of channels  120  are prepared by forming a plurality of channels  120  through a single cylindrical support  110  by means of an etching process or by binding several conduits formed in a single channel  120 . 
     In order to selectively detect, analyze and transfer a plurality of nerve signals by using the nerve conduit  100  configured as above, the present disclosure uses a wireless communication manner and an artificial nerve network. 
     Hereinafter, the configuration and operations of the peripheral nerve interface unit  200  according to the present disclosure will be described in detail with reference to  FIGS. 5 and 6 . 
       FIG. 5  is a detailed diagram showing a peripheral nerve interface unit applied to the peripheral nerve interface system according to an embodiment of the present disclosure. 
     Referring to  FIG. 5 , the peripheral nerve interface unit  200  includes an internal module  220  and an external module  240 . 
     The internal module  220  includes a first digital signal processing unit  221 , a first AD converter  222 , a DA converter  224 , a first amplifying unit  226 , a stimulating unit  227 , a multiplexer  228 , a first communication unit  225 , a wireless power receiving unit  223  and a first battery unit  229 . 
     The roles of the first digital signal processing unit  221 , the first amplifying unit  226 , the stimulating unit  227 , the first communication unit  225  and the nerve regenerating electrode  7  have been described in relation to  FIG. 1  and thus are not described in detail here. 
     The multiplexer  228  plays a role of selectively matching the efferent motor nerve signals received from a plurality of ‘connection electrodes’, namely the second connection unit  142 , with a limited number of the first amplifying units  226  and the stimulating units  227 . 
     The multiplexer  228  performs this matching operation according to an instruction of the first digital signal processing unit  221 , and the first digital signal processing unit  221  performs such operations by using the multilayer perceptron algorithm. 
     The first AD converter  222  converts the efferent nerve signal amplified by the first amplifying unit  226  from an analog signal to a digital signal so that the first digital signal processing unit  221  may analyze the efferent nerve signal. 
     The DA converter  224  plays a role of converting the digital signal transferred from the first digital signal processing unit  221  into an analog signal. 
     As described above in relation to  FIG. 1 , the first communication unit  225  plays a role of transmitting and receiving the efferent motor nerve signal and the afferent sensory signal to/from the second communication unit  245  of the external module  240  in a wireless communication manner. As shown in  FIG. 5 , the first communication unit  225  may include an RF antenna  225   a.    
     The wireless power receiving unit  223  receives power from the external module  240  in a wireless manner and supplies the power to the first battery unit  229 . The first battery unit  229  is charged with the supplied power and supplies power to the first digital signal processing unit  221  or the like. 
     As shown in  FIG. 5 , the wireless power receiving unit  223  may include a power coil  223   a  for receiving power. The power coil  223   a  of the wireless power receiving unit  223  is supplied with power from the power coil  243   a  of the wireless power transmitting unit  243  of the external module  240  in a wireless communication manner. The wireless power transmission method using electromagnetic induction is well known in the art and thus not described in detail here. 
     The external module  240  includes an embedded controller  241 , a second digital signal processing unit  242 , a wireless power transmitting unit  243 , a second battery unit  244 , a second communication unit  245 , a second AD converter  246 , a PC communication module  247  and a second amplifying unit  248 . 
     The second battery unit  244  supplies power to the second digital signal processing unit  242  or the like, and the wireless power transmitting unit  243  receives power from the second battery unit  244  and supplies the power to the wireless power receiving unit  223  of the internal module  220  in a wireless manner. The wireless power transmitting unit  243  includes a power coil  243   a , similar to the internal module  220 . 
     The second communication unit  245  plays a role of transmitting and receiving signals to/from the first communication unit  225  of the internal module  220  and is configured to include an RF antenna  245   a.    
     The second AD converter  246  plays a role of receiving the sensory signal detected by the sensor  310  of the prosthesis  300  and converting the sensory signal into a digital signal. 
     The second digital signal processing unit  242  plays a role of receiving the digital signal from the second communication unit  245  and the second AD converter  246  and then analyzing and processing the digital signal. In detail, the second digital signal processing unit  242  analyzes the efferent motor nerve signal of the peripheral nerve  10  received by the second communication unit  245 , and transmits the analysis result to the embedded controller  241  in order to control the prosthesis  300 . In addition, the second digital signal processing unit  242  analyzes the sensory signal converted into the digital signal by the second AD converter  246  and transmits the sensory signal to the internal module  220  through the second communication unit  245 . 
     The embedded controller  241  receives the efferent motor nerve signal from the second digital signal processing unit  242  as described above, and then generates an actuator control signal corresponding thereto and transmits the actuator control signal to the second amplifying unit  248 . 
     The second amplifying unit  248  amplifies the received actuator control signal and transfers the amplified actuator control signal to an actuator  320  of the prosthesis  300 . The actuator  320  is a module for controlling a joint of the prosthesis  300  and is installed in the prosthesis  300 . 
     The PC communication module  247  is installed to operate the external module  240  in linkage with an external PC  400 . In other words, the external module  240  may be connected to the external PC  400  through the PC communication module  247  to provide a user with the processing situation of the second digital signal processing unit  242  through a screen of the PC  400 . 
       FIG. 6  is a conceptual diagram for illustrating a signal transmission operation of the peripheral nerve interface system according to an embodiment of the present disclosure. 
     The first digital signal processing unit  221  of the internal module  220  and the second digital signal processing unit  242  of the external module  240  transmit or receive signals in a wireless manner. The first digital signal processing unit  221  receives the efferent motor nerve signal generated by the peripheral nerve  10  of the cut body portion of a patient and transmits the efferent motor nerve signal to the second digital signal processing unit  242 . The second digital signal processing unit  242  generates an actuator control signal corresponding to the efferent motor nerve signal to control operations of the prosthesis  300 . 
     On the contrary, the second digital signal processing unit  242  receives the sensory signal detected by the sensor  310  of the prosthesis  300  and converts the sensory signal into a digital signal, and transmits the converted signal to the first digital signal processing unit  221 . 
     Then, the first digital signal processing unit  221  generates an afferent electric stimulation signal corresponding to the sensory signal and transfers the afferent electric stimulation signal to a nerve cell regenerated at the terminal of the peripheral nerve  10 . 
     The electric stimulation pattern is formed by applying afferent electric stimulation pulses to a peripheral nerve regenerated at a nerve electrode located in the porous polymer nerve conduit  100 . The regenerated peripheral nerve is classified into an efferent axon and an afferent axon. 
     Therefore, the peripheral nerve interface unit  200  sets paths according to the kinds of efferent axons to propagate efferent signals and afferent signals so that the efferent nerve electrode may be connected to the amplifying unit  226  and the afferent nerve electrode may be connected to the stimulating unit  227 . The path setting method may adopt a multilayer perceptron algorithm widely known in the art. 
     The input/output of the peripheral nerve interface algorithm are set according to the path setting, and accordingly the prosthetic hand, namely the prosthesis  300 , is bound as a single closed loop, which may overcome the limit of an existing open loop. 
       FIG. 7  is a diagram showing a prosthesis applied to the peripheral nerve interface system according to an embodiment of the present disclosure. 
       FIG. 7  depicts a prosthetic hand model as an example of the prosthesis  300 . The prosthesis  300  may have multiple joints and multi-degree of freedom for natural movement and may be designed similar to a hand or foot of a human. 
     The sensor  310  for measuring a sensory signal is installed at the prosthesis  300  of  FIG. 7 , namely at the finger of the prosthetic hand, and the measured sensory signal is analyzed at the digital signal analyzing unit of the peripheral nerve interface unit  200  and transferred as an afferent nerve signal. 
     In addition, according to the efferent motor nerve signal transmitted from the internal module  220 , the embedded controller  241  of the external module  240  generates and transmits the actuator control signal for controlling the prosthesis  300 . 
     The peripheral nerve interface system and method according to the present disclosure controls a prosthetic hand by using the feedback of a nerve signal of the peripheral nerve remaining at the cut portion and a sensory signal measured by the sensor of the prosthetic hand, thereby allowing the prosthetic hand to be controlled similar to actual hand movements. 
     While the exemplary embodiments have been shown and described, it will be understood by those skilled in the art that various changes in form and details may be made thereto without departing from the spirit and scope of the present disclosure as defined by the appended claims.