| Summary: | 博士 === 國立中興大學 === 材料科學與工程學系所 === 107 === This study uses the electrochemical technology to modify the surface and develop by INTAI Technology Corporation. The use of medical grade AISI440A stainless steel and the manufacture of laparoscopic minimally invasive scalpel for surface modification. In order to consider the production in the future, saving process time, operating voltage control is 5~8V, and the process time is 3~6 min. And use AISI440A stainless steel sheet as auxiliary experiment, to form a Cr2O3 layer, increases hydrophobicity, and has anti-adhesion. We hope to invest in the minimally invasive surgery instruments market and anti-adhesion technology that improve tissue adhesion problems in laparoscopic instruments. Materials were used to analyze the structure, crystallization characteristics, surface roughness, surface morphology and thickness of the Cr2O3 layer to aid in corrosion resistance testing including electrochemical dynamic polarization and salt spray testing, and contact angle testing for hydrophobic surface. The mechanism of AISI440A stainless steel on the surface of minimally invasive surgical instruments to form a Cr2O3 layer was proposed.
In material analysis, X-ray diffraction results show that the structure of the Cr2O3 layer is a rhombohedron. There is an α-Cr2O3 phase. The formation of a Cr2O3 layer on the sheet to produce the diffraction peak of (300) and (202) plane and the formation of a Cr2O3 layer layer in a minimally invasive scalpel that produce the diffraction peaks of (300), (202), and (024) plane. Analysis of texture coefficient, the formation of a Cr2O3 layer on the sheet enhances the (202) plane with a texture coefficient of 1.18 and greater than 1, with a preferred crystallographic orientation. The formation of a Cr2O3 layer layer on a minimally invasive scalpel also enhances the (202) plane with a texture coefficient of 2.17. Through the auxiliary experimental results for AISI440A stainless steel sheet, surface roughness measurement and SEM surface topography observation show that the surface roughness(Ra) was reduced to 15.33 nm for 6 min, the surface topography became flat, and the surface morphology with oxygen pore. SEM cross sectional observation show that the formation of a Cr2O3 layer on the sheet and the thickness reach to 45μm for operating voltage control is 8V, process time is 6 min and is confirmed by the EDS line scan analysis.. The Cr2O3 layer formed on the minimally invasive scalpel can reach 5 μm.
In corrosion resistance testing, electrochemical dynamic polarization curve results show that the corrosion potential (Ecorr) reduced to −230 mV due to AISI440A stainless steel is affected by the galvanic corrosion. After surface modification to form a Cr2O3 layer, the operating voltage is 8V, the process time is 6 min, the potential in the passivation region of the dynamic polarization curve is increased to 650 mV, and the corrosion current is reduced to 0.94 μA/cm2. And corresponding to the weather resistance test of salt spray 2hr, can improve corrosion resistance. In contact angle testing for hydrophobic surface, the surface is modified to form a Cr2O3 layer, the operating voltage is 5V, the process time is 3 min, and the surface roughness (Ra) is 30.22 nm, which can increase the contact angle to 101.5±2.5°, reduce the surface free energy and increase the hydrophobicity.
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