The Flexible ECG Microelectrode Arrays Based On Gecko Bionic Structure

Gecko lizards have excellent climbing ability in nature. The ability to maneuver on different smooth and rough surfaces, even ceilings.The gecko's adhesive ability is attributed to its multi-tiered hierarchy structure in its palm which has micro-size rigid hair structure and nano-size fluff structure, leading to a large van der Waals force when in contact with surface. The structure of the gecko's palm has been widely used in the applications of micro electromechanical systems(MEMS) and climbing robotics. In this work, we apply this gecko's palm structure to biological medical devices. Stretchable electronic sensors are designed with the ideas, which can adhere to human skins to monitor physiological signals. The thesis is focused on investigation of the simulation of the gecko's palm structure and processing of the stretchable electronic sensor.There are many processing methods to produce the fiber rod arrays as simulation of the gecko's palm structure. In this work, two techniques are adopted. One is to use SU-8, a lithography photoresist, to make the molds of fiber rod arrays. First, polydimethylsiloxane(PDMS) is injected into the mold to form the fiber rod arrays. Since the minimum size of the arrays is only about 3?m, it is difficult for the lithography to make the aperture array mold, and also the height of the arrays is far less than that designed. The other method is to apply silicon etching technique, using ICP etching process to make three different sizes of silicon molds, and then PDMS is poured into the molds to form the simulated gecko's array structure. When the diameter of the arrays is less than 3?m, entanglement phenomenon will occur. Through a simple adhesive measuring device, it is found that the fiber rod arrays can bear a maximum load of 1.1N.So far electrocardio signals have played a crucial role in clinical applications. Conventional disposable Ag/Ag Cl electrodes cannot be used to monitor human's health conditions for a long term. Also the conducting resin on the electrodes will cause allergic reaction to the skin. With the development of biology science, information technology and material science, biological sensors have been widely applied. Stretchable electronic technique is achieved. In this work, we design a new type of stretchable sensor composed of titanium and gold sputtered onto the PDMS flexible substrate with fiber arrays mimicking the gecko's palm structure. Compared to the Ag/Ag Cl electrodes, this stretchable sensor has several advantages. First, there is no need for conducting resin as connection with the skin. The stretchable sensor can be directly in contact with the skin, preventing from the allergy caused by the conducting resin. Also PDMS is colorless, tasteless, nontoxic and bio-compatible material. The gecko-like fiber array structure on the both sides of the electrode can stick the stretchable electrodes onto the skin firmly. Secondly, the stretchable electrodes can be recycled without affecting the quality of electrocarido signals. Thirdly, the stretchable electrodes have the great stretchability,which helps them applied in bending condition. Lastly, the quality of electrocardio signal obtained by the stretchable electrodes is comparable to that of conventional Ag/Ag Cl ones.