Research On The Key Technology And Application Of Flexible Metal Nanostructured Actuator Manufacturing

Flexible electronic devices are mainly based on flexible materials,combined with micro nano processing and integrated manufacturing process,through structural design,they are made into components with sensing,data storage,energy conversion and other functions,which have great application prospects in aerospace,biomedical,information sensing and other fields.With the rapid development of medical devices based on MEMS micro actuator,as the key component of flexible medical devices,microelectrode array actuator has been widely concerned.Microelectrode array（MEAs）refers to the actuator structure that conducts signals between electronic devices and living cell tissues.It can stimulate nerves or muscles and record electrical signals from receptors or motor fibers.Due to the high electrical impedance,low adhesion and biocompatibility of electrode devices,the micro actuator has encountered many bottlenecks in the process of medical detection,biosensor,micro robot and other experiments.The main reason is that the electrode impedance is too large,which leads to the need to apply large current in the process of electrode stimulation and recording.This situation will not only seriously damage the skin and tissue at the contact position,but also greatly reduce the adhesion between the metal and polymer layer,leading to the rapid failure of microelectrode.In addition,due to the mismatch of Young’s modulus between the polymer flexible material and the metal coating,the flexible electrode is easy to fall off in the long-term implantation process.Therefore,in order to develop a flexible electrode device with high adhesion and low impedance,it is of great scientific significance and application value to improve the key technology in the manufacturing process.In this thesis,the reactive ion dry etching and the micro contact printing in soft lithography are used to study how to process and prepare microelectrode actuators with different nanostructures by a new process,so that they have low impedance,high adhesion and excellent tensile and torsional properties.Based on the flexible microelectrode array,which is an important executive electronic device in neural stimulation/recording,this paper focuses on the key technologies in the field of manufacturing flexible electrode executive devices with nanostructures.The main purpose is to improve the electrical and mechanical properties of electrode array with metal conductive layer through different manufacturing process steps.In particular,the adhesion between the polymer flexible material and the metal coating,as well as the impedance of the interface between the conductive metal layer and the organism.Based on the theory of adhesion mechanics,the molecular force of metal layer on the surface of flexible metal substrate film is analyzed.Through the establishment of nano indentation test model and nano scratch test model between flexible polymer material and conductive metal layer,the elastic modulus of the surface metal layer is expressed,and the changes of film hardness,friction coefficient and indentation depth are further analyzed.At the same time,the COMSOL multiphysics finite element simulation method is used to further study the relationship between the contact size of the flexible electrode and the heat generated in the retinal model.Based on MEMS technology,the flexible metal electrode actuator was fabricated,and the relatively complete manufacturing process of 10 channel and 126 channel neural stimulation/recording flexible electrode was obtained.In this paper,the whole process is optimized from the reactive ion etching（dry etching）stage in the MEMS process.After etching,the concave convex nanostructure model is used to improve the adhesion between the metal layer and the polymer flexible substrate.In order to further optimize the electrical properties of the electrode contact,this paper further reduces the impedance of the coating surface,improves the charge storage capacity and contact surface area of the flexible electrode coating interface by electroplating different 3D nano morphology structure on the electrode contact.Through the analysis of nano indentation and nano scratch morphology of the film,the concave convex nanostructure on the flexible substrate can affect the cohesive force of the film to a certain extent in the process of nano scratch film damage from the first stage to the third stage.A new implantable flexible electrode actuator was fabricated by using micro contact printing（μCP）technology,PDA biomimetic coating as intermediate buffer layer and ptnw as conductive metal layer.Through the micro contact printing pressure,the film thickness and the surface impedance after the micro printing process were studied.Based on the biomimetic adhesion of PDA film material,the mismatch of Young’s modulus between the base layer and the metal layer is improved at the molecular level,and the improvement of adhesion performance is studied by using the mechanical fatigue life test method（ultrasonic vibration,torsional fatigue test）.The electrical properties of PI-PDA/Pt NW flexible electrode and its comparison with that of PI Ti/Pt flexible electrode were tested in vitro.By using nano-TiO₂ particles to accelerate the deposition of PDA biomimetic film coating,this processing scheme has important research value for the characteristics of electron transfer on the surface of PDA under light and the accelerated deposition mechanism of platinum metal nanostructure coating,and then through this process,the rapid manufacturing process of flexible metal coating electrode actuator is obtained.By adding nano-Ti O₂ semiconductor materials to the inner and surface of PDA coating film,the bottleneck of long in-situ growth of PDA biomimetic coating materials and platinum nanowires was solved,and the manufacturing process of flexible electrode device was accelerated.Based on the phenomenon of electron hole separation on the surface of nanoTi O₂,the linear relationship between the polarization current properties and the UV light intensity was studied.The detection gap between the flexible electrode and the current commercial electrode was analyzed through the implanted rat experiment.It mainly analyzes the system construction of animal experiment platform,animal operation experiment,signal acquisition and processing,and processes and compares three different kinds of electrode signals.The signal-to-noise ratio（SNR）and the density of action potential（AP）measured by the flexible PDA/Pt NW microelectrode were compared.To sum up,we first developed a manufacturing process of flexible neural electrode devices by magnetron sputtering,dry etching,wet etching and other processes,and obtained a complete process parameter of bump nanostructure reinforced metal layer and polymer layer by optimizing the manufacturing process of plasma etching.By controlling the concentration of formic acid solution and the electroplating potential,a kind of 3D barrier like nano dense structure was obtained,which can increase RMS to 116.5 nm and reduce the impedance to 0.824 kΩ.The mismatch of Young’s modulus between polymer and metal layer is improved in the molecular field by using the soft lithography method and the polydopamine adhesive biomimetic material.Then,the cost of fabrication is reduced by micro contact printing.The conductive metal layer of Pt nanowires is grown in situ by chemical self-assembly process,and the surface area of the coating is large.Through the electron transfer effect of nano titanium dioxide under UV light,rapid oxidation of PDA biomimetic coating synthesis and reduction of platinum metal conductive metal coating,the overall manufacturing time is shortened by about 16 times.The performance of platinum iridium alloy electrode in animal nerve recording and stimulation was tested by building animal experimental platform and referring to the widely used commercial platinum iridium alloy electrode.This research has important scientific significance and application value for the key technology breakthrough of the future flexible electrode actuator manufacturing.