| Facial nerve damage can cause facial paralysis, which will make patients losefacial function. It not only affects the appearance of the human face, but also makesthe facial organs work abnormally. And it may even lead to blindness which caused bylosing the protection of the eyelids and not being able to moist the eyes because ofmalfunction of closing eyes, which may seriously affect people’s normal life.Currently, the main methods for the treatment of facial nerve paralysis include nervetransplantation, instrumental treatment and electrical stimulation. Nervetransplantation therapy is limited in clinical application due to insufficient availablenerve quantity of transplantation, the probability of causing complications aftersurgery, poor biocompatibility of artificial nerve material and so on. And this methodhas little cure probability for the patients with their facial nerve seriouslydamaged.The instrumental treatment method is also limited due to its inconvenience,poor aesthetics effect and poor utility. Electrical stimulation can make paralyzedmuscle contract, which is widely used in functional electrical stimulation (FES) andtherapeutic applications. And it will be helpful to restore facial function of the patientswith facial nerve seriously damaged by FES of muscle after the implantation ofimplantable microsystems based-on MEMS technology.This paper focuses on the research based-on electrical stimulation for artificialfacial nerve repairing technology. In this paper, an implantable artificial facial nervetechnology based-on flexible MEMS technology is proposed based-on the researchachievements worldwide, which includes microelectrode technology, systemintegration technology, system power supply technology and electrical stimulationtechnology. The research on the system structure of facial nerve treatment and theeffects of the key technologies of the system are carried on. And the research on thedesign and fabrication process of thes parts of the system are also carried on. Moreover, the animal experiment is also conducted. The main work of this paper is asfollows:1. A Parylene-based platinum-black coated wire microelectrode withmulti-electrode sites for electrical stimulation is researched. The research on thefabrication process of the wire microelectrode is carried on. During the fabrication,platinum and Parylene C with good biocompatibility are applied as electrode andpackaging materials, respectively. And by lift-off process, the microelectrodes can beeasily fabricated. Meanwhile, the research on electrode surface modificationtechnology to optimize the electrochemical performance is also conducted.Platinum-black coatings fabricated on electrode sites by current pluses electroplatingunder ultrasonic bath will significantly decrease the impedance and increase thecharge storage capacity of electrodes. And the grain refinement during electroplatingprocess can lead to strong adhesion between coatings and substrates which will ensuregood mechanical stability of electrodes. Compared with constant potentialelectroplating process, the decline of CSCc of the coatings by current pluseselectroplating under ultrasonic bath is only just1/3of that after ultrasonic vibrationprocess. Furthermore, the slight change of CSCc after2.19×108current pulsesdemonstrates the excellent electrochemical stability. And the bending test also showsgood bending stability of the wire microelectrode. During8month of acceleratedlife-time soaking in0.9%saline at87℃(equivalent to21years at37℃),the stabilityof impedance and CSCc also demonstrates the long-term stability of electrodes afterimplantation. For the evaluation of the biocompatibility of the platinum-black coatedmicroelectrodes, the microelectrodes are implanted in the muscle of rabbits for twoweeks, and the results shows the same reaction between tissue and electrodescompared to platinum microelectrodes which means the good biocompatibility of theplatinum-black coated micoelectrode.2. A Parylene-based hemisphere microelectrode array is researched. The researchon the fabrication of the hemisphere microelectrode array is conducted. Duringfabrication process, the photoresist hot melt reflow technology and MEMS technologyare applied to form hemisphere shape. The electricity and mechanics simulation of themodel of the hemisphere microelectrode is also carried on. And the electroplatingprocess described above is also applied to form platinum-black coatings on electrodesites so as to improve the electrochemical characteristics of the microelectrodes. Inaddition, the electrode impedance test is also conducted, and the result shows that the hemispherical electrodes have lower impedance compared with the plane electrodeswith the same bottom area.3. A flexible MEMS-based chip and electrode multi-layer interconnectiontechnology is researched. The research on the fabrication process of the structure ofchip and electrode multi-layer interconnection is carried on. PDMS is applied assubstrate material for improving integration as well as decreasing the size of system.Compared to the conventional single-layer interconnection structure, the number ofelectrodes interconnected to chip of multi-layer interconnection structure is increasedwithin the same surface area. Moreover, using PDMS as substrate could greatlyreduce the processing costs in comparison to using silicon as substrate. In addition,using flexible Parylene thin film as the insulation layer will also make the wholestruct flexible.4. A transdermal recharging technology for recharging implantable devices isresearched. The single-needle and double-needle based transdermal rechargingdevices are designed and fabricated, respectively. For the former type, chargingprocess is validated by the tight fit between double-layer metal nets of the socket andneedle plug. Around the whole area of metal nets, the needle plug will form goodelectrical connection with battery for charging. During the insertion process withdifferent insertion angles, the contact impedance with the stable value of less than1demonstrates the good electrical connection. And after the insertion, the potential ofthe battery in a stable value could be measured from the needle plug by a multimeterdemonstrates the good operability. PDMS as encapsulation shell with goodbiocompatibility and flexibility demonstrates good waterproofness for preventingtissue fluid infiltrating into device after a set number of punctures. Moreover, theresult shows the low insertion force for easy insertion. For the latter type, two layersof metal nets of the socket were placed in the same plane for thickness reduction. Andit also has the characteristics of the former.5. The stimulation and recroding technologies are researched, including theschematics of stimulation and recroding system and their circuits. The animalexperiments of EMGs recording and orbicularis oculi muscle stimulation areconducted. During EMGs recording experiment, three groups of microelectrodes withdifferent area of electrode sites are used to recording the EMGs of the same rabbits inthe same position of orbicularis muscle with the rabbit eyes in the condition ofcontinuous closure, continuous opening and closure by stimulating. Then, the recorded EMGs are compared in time domain and frequency domain. The resultshows that the larger the area of electrode site is, the higher the amplitude and thepower of EMGs record by the electrode is. And a group of recording electrodes areused to recording the EMGs of the four states of the orbicularis muscle, too. Theresult shows that the highest value of the amplitude and the power of EMGs is thestate of closing eye by stimulating. During electrical stimulation experiment, chargeimbalance biphasic current pulse is use to stimulate the rabbit orbicularis oculi musclein open-loop and closed-loop conditions, respectively, which achieves good results. |
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