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<p>Helicoidal electrodes are placed surrounding the nerve and are made of flexible metal ribbon in a helical design. This design allows the electrode to conform to the size and shape of the nerve to minimize mechanical trauma. The structural design causes low selectivity. Helicoidal electrodes are currently used for functional electrical stimulation, to control intractable epilepsy, sleep apnea, and to treat depressive syndromes.</p> | <p>Helicoidal electrodes are placed surrounding the nerve and are made of flexible metal ribbon in a helical design. This design allows the electrode to conform to the size and shape of the nerve to minimize mechanical trauma. The structural design causes low selectivity. Helicoidal electrodes are currently used for functional electrical stimulation, to control intractable epilepsy, sleep apnea, and to treat depressive syndromes.</p> | ||
</div> | </div> | ||
− | <div class="block title"><h3 style="text-align: left;">2. Cuff electrode:</h3></div> | + | <div class="block title"><h3 style="text-align: left;">2. Cuff electrode <sup>[2]</sup>:</h3></div> |
<div class="block full"> | <div class="block full"> | ||
<p>Considered as extraneural electrodes, cuff electrodes are widely used to perform basic and applied electro-neurophysiology studies and are particularly interesting for their ability to achieve good nerve recruitment with low thresholds. The cuff-style electrode provides a cylindrical electrode contact with a nerve for each of an arbitrary number of contacts, is easy to place and remove in an acute nerve preparation, and is designed to fit on the nerve (Cf. Figure 1). For each electrode, the electrical contacts were cut from metal foil as an array so as to maintain their positions relative to each other within the cuff. Lead wires were soldered to each intended contact. The structure was then molded in silicone elastomer, and individual contacts were electrically isolated. The final electrode is curved into a cylindrical shape with an inner diameter corresponding to that of the intended target nerve. These electrodes have been successfully used for nerve stimulation, recording, and conduction block in a number of different acute animal experiments by several investigators.</p> | <p>Considered as extraneural electrodes, cuff electrodes are widely used to perform basic and applied electro-neurophysiology studies and are particularly interesting for their ability to achieve good nerve recruitment with low thresholds. The cuff-style electrode provides a cylindrical electrode contact with a nerve for each of an arbitrary number of contacts, is easy to place and remove in an acute nerve preparation, and is designed to fit on the nerve (Cf. Figure 1). For each electrode, the electrical contacts were cut from metal foil as an array so as to maintain their positions relative to each other within the cuff. Lead wires were soldered to each intended contact. The structure was then molded in silicone elastomer, and individual contacts were electrically isolated. The final electrode is curved into a cylindrical shape with an inner diameter corresponding to that of the intended target nerve. These electrodes have been successfully used for nerve stimulation, recording, and conduction block in a number of different acute animal experiments by several investigators.</p> | ||
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<div class="block title"><h3 style="text-align: left;">3. FINE electrode:</h3></div> | <div class="block title"><h3 style="text-align: left;">3. FINE electrode:</h3></div> | ||
<div class="block full"> | <div class="block full"> | ||
− | <p>The flat-interface nerve electrode (FINE) was designed for selective nerve recording by realigning the fascicles and reshaping the nerve into a more flattened cross section which increases the surface area of the exposed nerve and offers greater access to fascicles. This kind of electrode is particularly interesting as it was possible to achieve more than 90% selectivity (Cf. Figure 2)</p> | + | <p>The flat-interface nerve electrode (FINE) was designed for selective nerve recording by realigning the fascicles and reshaping the nerve into a more flattened cross section which increases the surface area of the exposed nerve and offers greater access to fascicles. This kind of electrode is particularly interesting as it was possible to achieve more than 90% selectivity <sup>[3]</sup> (Cf. Figure 2)</p> |
<img src="https://static.igem.org/mediawiki/2018/e/e3/T--Pasteur_Paris--ElectrodeFigure2.jpg" style="width:300px"> | <img src="https://static.igem.org/mediawiki/2018/e/e3/T--Pasteur_Paris--ElectrodeFigure2.jpg" style="width:300px"> | ||
− | <div class="legend"><b>Figure 2: </b>Cross section and schematic of a FINE electrode<sup>[ | + | <div class="legend"><b>Figure 2: </b>Cross section and schematic of a FINE electrode<sup>[4]</sup></div> |
</div> | </div> | ||
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<p>The most relevant information to extract is the discharge frequency of active fibers because it represents the means of coding information by the nervous system. Significantly, such processing must be applied to signals representing the activity of a limited number of fibers. In fact, the published examples relate exclusively to intra-neural collection: the only method, today, which allows to observe the activity of fibers alone. However, since we don’t want to use intra-neural electrode in our device we will not detail how to extract the discharge frequency.</p> | <p>The most relevant information to extract is the discharge frequency of active fibers because it represents the means of coding information by the nervous system. Significantly, such processing must be applied to signals representing the activity of a limited number of fibers. In fact, the published examples relate exclusively to intra-neural collection: the only method, today, which allows to observe the activity of fibers alone. However, since we don’t want to use intra-neural electrode in our device we will not detail how to extract the discharge frequency.</p> | ||
</div> | </div> | ||
− | <div class="block title"><h3 style="text-align: left;">2. Envelope extraction:</h3></div> | + | <div class="block title"><h3 style="text-align: left;">2. Envelope extraction <sup>[5]</sup>:</h3></div> |
<div class="block full"> | <div class="block full"> | ||
<p>Rectification and Bin-Integration (RBI) of the nerve raw signal is widely used in rehabilitation application. This point of RBI ENG is found by calculating the average of the absolute value of ENG samples spread over a given period of time. This period is called “bin” and its value depends on the application. It ranges from 10 ms to 200 ms. The smoothed envelope-like signal created by RBI makes it easy to extract information about the innervated organ.</p> | <p>Rectification and Bin-Integration (RBI) of the nerve raw signal is widely used in rehabilitation application. This point of RBI ENG is found by calculating the average of the absolute value of ENG samples spread over a given period of time. This period is called “bin” and its value depends on the application. It ranges from 10 ms to 200 ms. The smoothed envelope-like signal created by RBI makes it easy to extract information about the innervated organ.</p> | ||
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<div class="block separator-mark"></div> | <div class="block separator-mark"></div> | ||
<div class="block title"><h1>III. Improvement of the electroneurogram records selectivity</h1></div> | <div class="block title"><h1>III. Improvement of the electroneurogram records selectivity</h1></div> | ||
− | <div class="block title"><h3 style="text-align: left;">1. ENG-EMG selectivity:</h3></div> | + | <div class="block title"><h3 style="text-align: left;">1. ENG-EMG selectivity <sup>[6]</sup>:</h3></div> |
<div class="block full"> | <div class="block full"> | ||
<p>The body is made so that a nerve is never very far from a muscle. However, the triggering and control of muscle contractions use a similar mechanism to the propagation of nerve impulses. Thus, the vicinity of a muscle is the seat of important extracellular currents because of the large number of muscle fibers excited simultaneously. The potential differences associated with these currents are called EMG, for electromyogram. Action potentials in muscle have mV amplitude, larger than a neural signal, and their spectra overlap. Minimizing these forms of interference is there for essential.</p> | <p>The body is made so that a nerve is never very far from a muscle. However, the triggering and control of muscle contractions use a similar mechanism to the propagation of nerve impulses. Thus, the vicinity of a muscle is the seat of important extracellular currents because of the large number of muscle fibers excited simultaneously. The potential differences associated with these currents are called EMG, for electromyogram. Action potentials in muscle have mV amplitude, larger than a neural signal, and their spectra overlap. Minimizing these forms of interference is there for essential.</p> | ||
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<p>Thus, the impact of EMG on the measurement is significantly attenuated, while the ENG is preserved</p> | <p>Thus, the impact of EMG on the measurement is significantly attenuated, while the ENG is preserved</p> | ||
<img src="https://static.igem.org/mediawiki/2018/2/21/T--Pasteur_Paris--ElectrodeFigure3.jpg" style="width:300px"> | <img src="https://static.igem.org/mediawiki/2018/2/21/T--Pasteur_Paris--ElectrodeFigure3.jpg" style="width:300px"> | ||
− | <div class="legend"><b>Figure 3: </b>Comparison of the potential in the cuff due to EMG and ENG sources. </div> | + | <div class="legend"><b>Figure 3: </b>Comparison of the potential in the cuff due to EMG and ENG sources <sup>[6]</sup>. </div> |
<p>The electronic realization of this treatment is very simple, it can be done in two different ways using either one or three differential amplifiers, these structures are named respectively "quasi-tripole" and "true-tripole" (Cf. Figure 4)</p> | <p>The electronic realization of this treatment is very simple, it can be done in two different ways using either one or three differential amplifiers, these structures are named respectively "quasi-tripole" and "true-tripole" (Cf. Figure 4)</p> | ||
<img src="https://static.igem.org/mediawiki/2018/2/2e/T--Pasteur_Paris--ElectrodeFigure4.jpg" style="width:300px"> | <img src="https://static.igem.org/mediawiki/2018/2/2e/T--Pasteur_Paris--ElectrodeFigure4.jpg" style="width:300px"> | ||
− | <div class="legend"><b>Figure 4: </b>(a) The QT amplifier configuration connected to a tripolar cuff. (b) The TT amplifier configuration.</div> | + | <div class="legend"><b>Figure 4: </b>(a) The QT amplifier configuration connected to a tripolar cuff. (b) The TT amplifier configuration <sup>[6]</sup>.</div> |
</div> | </div> | ||
− | <div class="block title"><h3 style="text-align: left;">2. Type of nerve fiber selectivity:</h3></div> | + | <div class="block title"><h3 style="text-align: left;">2. Type of nerve fiber selectivity <sup>[7]</sup>:</h3></div> |
<div class="block full"> | <div class="block full"> | ||
<p>Nerves carry a lot of different neural signals, with both afferent and efferent traffic. However, by recording the signal we reduce it to only one artificial signal and we lose a lot of information. As the different types of signals are transmitted by fibers of different diameters, it should be interesting to select the fiber we record according to its diameter.</p> | <p>Nerves carry a lot of different neural signals, with both afferent and efferent traffic. However, by recording the signal we reduce it to only one artificial signal and we lose a lot of information. As the different types of signals are transmitted by fibers of different diameters, it should be interesting to select the fiber we record according to its diameter.</p> | ||
<p>The method (Cf. Figure 5) uses a double differential array of amplifiers ('tripole amplifiers') and, for each selected velocity (of either sign), artificial time delays, as well as an adder and a narrow-band filter. An action potential transiting the nerve will be perceived in the same way by each tripole, but with delays inversely proportional to the speed of propagation of the action potential. If this time offset is compensated by the delay added by the measurement system, the action potentials appear simultaneously at the output of the delay stages. Thus, summing them to each other, the amplitude of the action potential is amplified. This system makes it possible to amplify the measurement for this particular action potential. Whereas, for another action potential having a different speed or direction of propagation, the amplification will not take place because the delay implemented in the system does not correspond to the delay due to the propagation of the action potential. This system is therefore selective for a given propagation speed.</p> | <p>The method (Cf. Figure 5) uses a double differential array of amplifiers ('tripole amplifiers') and, for each selected velocity (of either sign), artificial time delays, as well as an adder and a narrow-band filter. An action potential transiting the nerve will be perceived in the same way by each tripole, but with delays inversely proportional to the speed of propagation of the action potential. If this time offset is compensated by the delay added by the measurement system, the action potentials appear simultaneously at the output of the delay stages. Thus, summing them to each other, the amplitude of the action potential is amplified. This system makes it possible to amplify the measurement for this particular action potential. Whereas, for another action potential having a different speed or direction of propagation, the amplification will not take place because the delay implemented in the system does not correspond to the delay due to the propagation of the action potential. This system is therefore selective for a given propagation speed.</p> | ||
<img src="https://static.igem.org/mediawiki/2018/0/0b/T--Pasteur_Paris--ElectrodeFigure5.jpg" style="width:300px"> | <img src="https://static.igem.org/mediawiki/2018/0/0b/T--Pasteur_Paris--ElectrodeFigure5.jpg" style="width:300px"> | ||
− | <div class="legend"><b>Figure 5: </b>Multi-electrode cuff (MEC), array of tripole amplifiers and signal processing unit for selecting one velocity. </div> | + | <div class="legend"><b>Figure 5: </b>Multi-electrode cuff (MEC), array of tripole amplifiers and signal processing unit for selecting one velocity <sup>[7]</sup>. </div> |
</div> | </div> | ||
− | <div class="block title"><h3 style="text-align: left;">3. Spatial selectivity:</h3></div> | + | <div class="block title"><h3 style="text-align: left;">3. Spatial selectivity <sup>[8]</sup>:</h3></div> |
<div class="block full"> | <div class="block full"> | ||
<p>Methods aim to increase the spatial selectivity of extra-neural electrodes to discriminate active fascicles, in order to determine the activity of each nerve branch.</p> | <p>Methods aim to increase the spatial selectivity of extra-neural electrodes to discriminate active fascicles, in order to determine the activity of each nerve branch.</p> | ||
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<div class="block separator-mark"></div> | <div class="block separator-mark"></div> | ||
− | <div class="block title"><h1>IV. An example of the development of a multi-channel acquisition device</h1></div> | + | <div class="block title"><h1>IV. An example of the development of a multi-channel acquisition device <sup>[9]</sup></h1></div> |
<div class="block full"> | <div class="block full"> | ||
<p>Olivier Rossel, in his thesis, chose to work on improving the selectivity of the cuff electrodes. He chose this type of electrode because they respect the integrity of the nerve and its fascicles membranes and that they make it possible to limit both the number of implants and the complexity surgical gesture. The electrode need reject the EMG signals and to measure local ENGs at multiple sites around the nerve.</p> | <p>Olivier Rossel, in his thesis, chose to work on improving the selectivity of the cuff electrodes. He chose this type of electrode because they respect the integrity of the nerve and its fascicles membranes and that they make it possible to limit both the number of implants and the complexity surgical gesture. The electrode need reject the EMG signals and to measure local ENGs at multiple sites around the nerve.</p> | ||
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<p>As we saw previously, it is possible to reject the EMG signal by using a tripolar cuff electrode (Cf. Figure 6). A tripolar cuff and the adapted electrical treatment is used.</p> | <p>As we saw previously, it is possible to reject the EMG signal by using a tripolar cuff electrode (Cf. Figure 6). A tripolar cuff and the adapted electrical treatment is used.</p> | ||
<img src="https://static.igem.org/mediawiki/2018/d/d7/T--Pasteur_Paris--ElectrodeFigure6.jpg" style="width:300px"> | <img src="https://static.igem.org/mediawiki/2018/d/d7/T--Pasteur_Paris--ElectrodeFigure6.jpg" style="width:300px"> | ||
− | <div class="legend"><b>Figure 6:</b> Schematic of a tripolar cuff electrode.</div> | + | <div class="legend"><b>Figure 6:</b> Schematic of a tripolar cuff electrode <sup>[9]</sup>.</div> |
</div> | </div> | ||
<div class="block title"><h3 style="text-align: left;">2. Tripolar treatment analysis</h3></div> | <div class="block title"><h3 style="text-align: left;">2. Tripolar treatment analysis</h3></div> | ||
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<div class="block title"><h3 style="text-align: left;">3. Electrode sizing</h3></div> | <div class="block title"><h3 style="text-align: left;">3. Electrode sizing</h3></div> | ||
<div class="block full"> | <div class="block full"> | ||
− | <p>n order to increase neural information relative to the noise, it is vital to optimize the cuff dimensions. The literature suggests that the best compromise between cuff length and the available place is a cuff length close to the wavelength of the transmembrane action potential. This one is approximately linear with fiber diameter.</p> | + | <p>n order to increase neural information relative to the noise, it is vital to optimize the cuff dimensions. The literature suggests that the best compromise between cuff length and the available place is a cuff length close to the wavelength of the transmembrane action potential. This one is approximately linear with fiber diameter <sup>[10]</sup>.</p> |
− | <p>According to Struijk, the action potential propagation velocity can be approximated as 55.800 nodes/s and the duration, of the transmembrane action potential, is approximately 0,4 ms.</p> | + | <p>According to Struijk <sup>[11]</sup>, the action potential propagation velocity can be approximated as 55.800 nodes/s and the duration, of the transmembrane action potential, is approximately 0,4 ms.</p> |
− | <p>Thus, to have an optimal measurement, the cuff electrode must cover 22 nodes of Ranvier. The inter-pole distance must, therefore, be adjusted to h = 11 | + | <p>Thus, to have an optimal measurement, the cuff electrode must cover 22 nodes of Ranvier. The inter-pole distance must, therefore, be adjusted to h = 11 l<sub>my</sub> (l<sub>my</sub> is the length of myelin separating two nodes of Ranvier). So, for a typical fiber, the inter-electrode distance h should be about 1 cm, which is used in most ENG measuring electrodes.</p> |
<img src="https://static.igem.org/mediawiki/2018/1/10/T--Pasteur_Paris--ElectrodeFigure7.jpg" style="width:390px"> | <img src="https://static.igem.org/mediawiki/2018/1/10/T--Pasteur_Paris--ElectrodeFigure7.jpg" style="width:390px"> | ||
− | <div class="legend"><b>Figure 7: </b>Extra-neural potential of monopolar action according to the position of the measuring point. The diagram at the top left shows the simulated situation. At the top right, the simulation corresponding to this configuration is represented: calculation of twice five monopolar potentials, for a typical axon (diameter of 8.7 <FONT face="Raleway">μ</FONT>m, and lmy= 1 mm). The distances from this axon to the measurement points are <FONT face="Raleway">ρ</FONT>1=100 <FONT face="Raleway">μ</FONT>m for site A and <FONT face="Raleway">ρ</FONT>2=500 <FONT face="Raleway">μ</FONT>m for site B. Below, the monopolar signals at points “a” to “e” are shown for each of the measurement sites.</div> | + | <div class="legend"><b>Figure 7: </b>Extra-neural potential of monopolar action according to the position of the measuring point. The diagram at the top left shows the simulated situation. At the top right, the simulation corresponding to this configuration is represented: calculation of twice five monopolar potentials, for a typical axon (diameter of 8.7 <FONT face="Raleway">μ</FONT>m, and lmy= 1 mm). The distances from this axon to the measurement points are <FONT face="Raleway">ρ</FONT>1=100 <FONT face="Raleway">μ</FONT>m for site A and <FONT face="Raleway">ρ</FONT>2=500 <FONT face="Raleway">μ</FONT>m for site B. Below, the monopolar signals at points “a” to “e” are shown for each of the measurement sites <sup>[9]</sup>.</div> |
<p>Knowing the characteristics of the electrode we want, it is possible to evaluate the distance h between the poles. This distance is of the order of a hundred micrometers which is much lower than that of a classical tripole which is of the order of a centimeter. This is why we will call, in the rest of this work, the tripole proposed a "small tripole".</p> | <p>Knowing the characteristics of the electrode we want, it is possible to evaluate the distance h between the poles. This distance is of the order of a hundred micrometers which is much lower than that of a classical tripole which is of the order of a centimeter. This is why we will call, in the rest of this work, the tripole proposed a "small tripole".</p> | ||
</div> | </div> | ||
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<p>For the small tripole, we have a fast attenuation depending on the distance compared to big tripole (Cf. Figure 8). As figure 8 confirms it, the small tripole is much more selective than the big tripole. Moreover, figure 9 shows that despite the low power level of the targeted signals and the spatial filtering performed, the peak-to-peak amplitude of the output signals of the tripole can reach 6 <FONT face="Raleway">μ</FONT>V for a single active fiber. Considering the superposition of signals - the simultaneous activity of several fibers - we can hope to reach larger amplitude. Even if it is the case, the output signals of a small tripole remain of very low amplitude and it will thus be necessary to be very attentive to the sources of noise to maintain an acceptable signal-to-noise ratio.</p> | <p>For the small tripole, we have a fast attenuation depending on the distance compared to big tripole (Cf. Figure 8). As figure 8 confirms it, the small tripole is much more selective than the big tripole. Moreover, figure 9 shows that despite the low power level of the targeted signals and the spatial filtering performed, the peak-to-peak amplitude of the output signals of the tripole can reach 6 <FONT face="Raleway">μ</FONT>V for a single active fiber. Considering the superposition of signals - the simultaneous activity of several fibers - we can hope to reach larger amplitude. Even if it is the case, the output signals of a small tripole remain of very low amplitude and it will thus be necessary to be very attentive to the sources of noise to maintain an acceptable signal-to-noise ratio.</p> | ||
<img src="https://static.igem.org/mediawiki/2018/f/fb/T--Pasteur_Paris--ElectrodeFigure8.png" style="width:300px"> | <img src="https://static.igem.org/mediawiki/2018/f/fb/T--Pasteur_Paris--ElectrodeFigure8.png" style="width:300px"> | ||
− | <div class="legend"><b>Figure 8: </b>Peak-to-peak amplitudes of the output action potential of a small tripole and of a big one</div> | + | <div class="legend"><b>Figure 8: </b>Peak-to-peak amplitudes of the output action potential of a small tripole and of a big one <sup>[9]</sup>.</div> |
<img src="https://static.igem.org/mediawiki/2018/b/b2/T--Pasteur_Paris--ElectrodeFigure9.jpg" style="width:300px"> | <img src="https://static.igem.org/mediawiki/2018/b/b2/T--Pasteur_Paris--ElectrodeFigure9.jpg" style="width:300px"> | ||
− | <div class="legend"><b>Figure 9: </b> Peak-to-peak amplitudes measure at the output of a big tripole (left) or a small tripole (right) in function of the position of the active axon (diameter 8, 7 <FONT face="Raleway">μ</FONT>m, and lmy=1 mm) in a cylindrical nerve of 300 <FONT face="Raleway">μ</FONT>m in diameter.</div> | + | <div class="legend"><b>Figure 9: </b> Peak-to-peak amplitudes measure at the output of a big tripole (left) or a small tripole (right) in function of the position of the active axon (diameter 8, 7 <FONT face="Raleway">μ</FONT>m, and lmy=1 mm) in a cylindrical nerve of 300 <FONT face="Raleway">μ</FONT>m in diameter <sup>[9]</sup>.</div> |
</div> | </div> | ||
<div class="block title"><h3 style="text-align: left;">6. Selectivity study:</h3></div> | <div class="block title"><h3 style="text-align: left;">6. Selectivity study:</h3></div> | ||
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<p>Olivier ROSSEL developed a new electrode architecture he compared to the FINE electrode. The FINE electrode used is the one developed by Paul YOO and Dominique DURAND (Cf. Figure 7).</p> | <p>Olivier ROSSEL developed a new electrode architecture he compared to the FINE electrode. The FINE electrode used is the one developed by Paul YOO and Dominique DURAND (Cf. Figure 7).</p> | ||
<img src="https://static.igem.org/mediawiki/2018/e/ec/T--Pasteur_Paris--ElectrodeFigure10.png" style="width:300px"> | <img src="https://static.igem.org/mediawiki/2018/e/ec/T--Pasteur_Paris--ElectrodeFigure10.png" style="width:300px"> | ||
− | <div class="legend"><b>Figure 10: </b>FINE electrode, h = 0,5 mm.</div> | + | <div class="legend"><b>Figure 10: </b>FINE electrode, h = 0,5 mm <sup>[9]</sup>.</div> |
<p>Olivier ROSSEL tried to improve this electrode replacing each measure point by a small tripole and by deleting two external ring. He called this electrode the FORTE electrode for “FINE with Original Recording Tripolar Electrode” (Cf. Figure 11). The main difference between these two electrodes is the inter-poles distance in the longitudinal way.</p> | <p>Olivier ROSSEL tried to improve this electrode replacing each measure point by a small tripole and by deleting two external ring. He called this electrode the FORTE electrode for “FINE with Original Recording Tripolar Electrode” (Cf. Figure 11). The main difference between these two electrodes is the inter-poles distance in the longitudinal way.</p> | ||
<img src="https://static.igem.org/mediawiki/2018/3/34/T--Pasteur_Paris--ElectrodeFigure11.png" style="width:300px"> | <img src="https://static.igem.org/mediawiki/2018/3/34/T--Pasteur_Paris--ElectrodeFigure11.png" style="width:300px"> | ||
− | <div class="legend"><b>Figure 11: </b>FORTE electrode, h = 375 <FONT face="Raleway">μ</FONT>m.</div> | + | <div class="legend"><b>Figure 11: </b>FORTE electrode, h = 375 <FONT face="Raleway">μ</FONT>m <sup>[9]</sup>.</div> |
<img src="https://static.igem.org/mediawiki/2018/9/93/T--Pasteur_Paris--ElectrodeFigure12.png" style="width:300px"> | <img src="https://static.igem.org/mediawiki/2018/9/93/T--Pasteur_Paris--ElectrodeFigure12.png" style="width:300px"> | ||
− | <div class="legend"><b>Figure 12: </b>Two fascicles represented in the electrode. These disposition of the fascicles is the one used for the simulations made to obtain figure 13 and figure 14</div> | + | <div class="legend"><b>Figure 12: </b>Two fascicles represented in the electrode. These disposition of the fascicles is the one used for the simulations made to obtain figure 13 and figure 14 <sup>[9]</sup>. </div> |
<p>The activity of two fascicles is simulated (Cf. Figure 12) and the peak-to-peak amplitudes of the output signals are compared (Cf. Figure 13). The first difference we see is the signal from the FORTE electrode is attenuated 20 dB compared to the FINE electrode. In figure 13, we see that when only one fascicle is active, the FORTE electrode makes it possible to locate the active fascicle much more easily than the FINE electrode.</p> | <p>The activity of two fascicles is simulated (Cf. Figure 12) and the peak-to-peak amplitudes of the output signals are compared (Cf. Figure 13). The first difference we see is the signal from the FORTE electrode is attenuated 20 dB compared to the FINE electrode. In figure 13, we see that when only one fascicle is active, the FORTE electrode makes it possible to locate the active fascicle much more easily than the FINE electrode.</p> | ||
<img src="https://static.igem.org/mediawiki/2018/4/43/T--Pasteur_Paris--ElectrodeFigure13.jpg" style="width:300px"> | <img src="https://static.igem.org/mediawiki/2018/4/43/T--Pasteur_Paris--ElectrodeFigure13.jpg" style="width:300px"> | ||
− | <div class="legend"><b>Figure 13: </b>Peak-to-peak tension received by the tripole n (from tripole 1 to tripole 13) for the red and black fascicles.</div> | + | <div class="legend"><b>Figure 13: </b>Peak-to-peak tension received by the tripole n (from tripole 1 to tripole 13) for the red and black fascicles <sup>[9]</sup>.</div> |
<p>Moreover, in the general case of a simultaneous activity of different fascicles, the signals from the different active fascicles are summed at the level of each tripoles (Cf. Figure 14). We can see that for the FINE electrode the amplitude measured makes it impossible to differentiate the active fascicles. However, for the FORTE electrode, since the small tripole is locally sensitive, we can’t see the difference between the figure 13 and the figure 14. It is easy to differentiate the active fascicles.</p> | <p>Moreover, in the general case of a simultaneous activity of different fascicles, the signals from the different active fascicles are summed at the level of each tripoles (Cf. Figure 14). We can see that for the FINE electrode the amplitude measured makes it impossible to differentiate the active fascicles. However, for the FORTE electrode, since the small tripole is locally sensitive, we can’t see the difference between the figure 13 and the figure 14. It is easy to differentiate the active fascicles.</p> | ||
<img src="https://static.igem.org/mediawiki/2018/9/9d/T--Pasteur_Paris--ElectrodeFigure14.jpg" style="width:400px"> | <img src="https://static.igem.org/mediawiki/2018/9/9d/T--Pasteur_Paris--ElectrodeFigure14.jpg" style="width:400px"> | ||
− | <div class="legend"><b>Figure 14: </b>Simulated ENG for FINE electrode (A) and for the FORTE electrode (B) for the two fascicles in the case of a simultaneous activity. The contribution of each fascicles is designed by the color avec the fascicles in the figure 13. Each fascicle contains around two hundred active axons.</div> | + | <div class="legend"><b>Figure 14: </b>Simulated ENG for FINE electrode (A) and for the FORTE electrode (B) for the two fascicles in the case of a simultaneous activity. The contribution of each fascicles is designed by the color avec the fascicles in the figure 13. Each fascicle contains around two hundred active axons <sup>[9]</sup>.</div> |
<p>Finally, we see the FORTE electrode can surpass in selectivity the FINE electrode. The FORTE electrode is a great example of an electrode we could use for our device.</p> | <p>Finally, we see the FORTE electrode can surpass in selectivity the FINE electrode. The FORTE electrode is a great example of an electrode we could use for our device.</p> | ||
</div> | </div> |
Revision as of 20:00, 16 October 2018
Membrane
When manipulating genetically engineered organisms, it is crucial to guarantee the confinement of these organisms. In our case, we want genetically modified bacteria to stay at the interface between the prosthesis and the external organic medium. At the same time, one of the main issues our project wants to tackle is the conduction of the neuron influx to the prosthesis. The answer to these questions came as a double solution: confinement of the bacteria by conductive nanoporous membranes. The membrane’s nanoporosity allows substances produced by our modified biofilm to pass through the membrane, but the bacteria remain confined. We tested the conductivity and biocompatibility of two types of membranes.
Membrane
Nerve and electrodes
As seen in the other parts of this wiki, we chose to use a nanoporous membrane in our device. The first goal of the membrane was to confine our biofilm, so it does not escape the prosthesis. Moreover, we also used our membrane as a conductive electrode. This solution was interesting since we didn’t have enough time to develop an entire electrical device which collects and treat the signal of the nerves. However, we know we still need to improve our interface if we want the patient to fully control his prosthesis. That is why we decided to look at what is already made in this field. So, first, we detailed how it is possible to model the electrical characteristics of a nerve. Then, we searched for information on electrodes and signal treatment.
This section is principaly based on the thesis of Olivier Rossel: Dispositifs de mesure et d’interprétation de l’activité d’un nerf. Electronique. Université Montpellier II - Sciences et Techniques du Languedoc, 2012. Français.