| Summary: | 博士 === 國立成功大學 === 航空太空工程學系碩博士班 === 98 === This dissertation investigates the mechanisms and performance of micro-jets and the penetration of micro-jets into soft solid materials using a homemade needle-free micro-jet injection system. The application of endoscopic tissue elevation using the needle-free micro-jet injection system also describes in this paper. The first part of this research is to study the characterization of the micro-jet. The experiments were performed using micro-jet with orifice 250 μm and 300 μm. The test results show that the micro-jet velocity increases from 40 m/s to 114 m/s as the injection pressure increased from 15 bar to 125 bar and result in the jet power from 1.7 W to 46.7 W. The injection force with the standoff distance of 2 mm increases from 10.3 to 96.4 g. The discharge coefficient, CD of both injectors is about 0.7 over the range of Reynolds numbers from 15,000 to 40,000. At lower values of Reynolds numbers (10,000 to 15,000), CD approaches 0.75. The second part describes the measurement of the mechanical properties using compression test and deep penetration test. Experimental results show that the Young’s modulus of 30% gelatin gel and porcine colon measured by compression test are 0.037±0.013 MPa and 0.0089±0.0036 MPa, respectively. The failure stress of 30% gelatin gel and porcine colon measured by deep penetration test are 0.694±0.043 MPa and 1.077±0.333 MPa, respectively. The performance of the pulsed micro-jet and its penetration on the solid soft material is described in the third part of this dissertation. According to the test results, it is concluded that the penetration of the micro-jets into solid soft materials is essentially controlled by the injection pressure and the orifice diameter. It is observed that the compression followed penetrated inside the gel after the micro-jet impingement. The micro-jet compression and penetration is increased along both the axial and transverse directions in the gel. As the pulsed micro-jet is stopped to supply water, the penetration reduces in both the axial and transverse directions. The penetration process can be divided into 4 phases, the elastic deformation phase, the penetrating phase, the elastic recovering phase and the stable phase. In the test case, the final penetration depth reaches 11.4 mm and 12.5 mm by using the orifice of 250 μm and 300 μm, respectively. The fourth part in this research applies the needle-free micro-injection system to endoscopic therapeutics. The performance of the endoscopic needle-free injection system on the tissue elevation of the porcine colon is investigated. The working fluids include normal saline, glycerin and alginate solutions. The tissue is first penetrated into the mucosal layer and lifted up due to the second-step injection of the working fluids into the tissue. It is then recovered due to the diffusion of the working medium to the neighboring tissue. The processes are recorded by the high speed camera for further analysis. Results show that the alginate solution with higher rheologic property has the advantage to supply higher flow rate under the same operational condition. Moreover, with the viscosity of 5 cp, the half-life time of the alginate solution is longer than that of the glycerin solution. Tests over the viscosity ranging from 5 cp to 30 cp with alginate solution indicate that the half-life time increases with viscosity and the half-life time is more than 60 min, which is long enough for the snare resection of the tumor through the endoscope.
We successfully applied this endoscopic needle-free micro-jet injection system in tissue elevation. After completion of this treatment technology, it will be applied to tumor treatment, such as the gastrointestinal tract, biliary tract, urinary tract, etc., to provide a convenient, economical and effective operation of endoscopic therapeutics.
|
|---|
