Study of Manufacturing of Miniature Intradiscal Pressure Transducers
Date Issued
2011
Date
2011
Author(s)
Huang, Chi-Hsuan
Abstract
Introduction: Needle-type transducers are widely used in measuring the intradiscal pressure (IDP). The manufacturing procedures of in-house miniature needle-type transducer (20G) are not well established, resulting in the poor yielding rate and large variances of sensitivity and nonlinearity. The yielding rate of transducer also needs to be improved. In order to tackle these problems, the aim of this study is to develop a standard protocol of miniature needle-type IDP transducer manufacturing.
Material and method: We designed a standard procedure for transducer manufacturing. At first, the strain gage was attached to a fillister in a 20G needle with gage-specific glue. The fillister was created with a method of electric discharge. The surface of the strain gage was covered by a layer of melted adhesive at 133℃. The amount of adhesive was quantified by a self-designed device. The flatness of adhesive surface was control by fixing the air-blow direction and using time of a heat gun. Then the transducer was sealed in a hydraulic device for calibration. Only the transducers with non-linearity less than 10% were selected for the next-step sustainability test. The sustainability test included a 30 min cyclic loading with the loading magnitude ranging from 0.4~0.7 MPa. After that the transducer was calibrated again. The screening criteria for the sustainability test of the transducer were 1) the nonlinearity <10% and 2) the changing ratio of the calibration coefficients <10%.
Result: This study compared the performances of needle transducers manufactured through standard protocol and manual protocol. Accordingly, fifty transducers were produced. A half of them were manufactured by the standard procedures (i.e. Standard group, n=25), while the other half was vice the versa (i.e. Manual group, n=25). The yielding rate was 72％ for the standard group and 24％ for the manual group. The average calibration coefficient of the standard group approached 20 bar / volt, which indicated proper sensitivity for IDP measurement. Compared to the manual group, the nonlinearity and standard deviation of calibration coefficient of the transducer were lower in the standard group.
Conclusion: The standardization of manufacturing procedures improves the stability and robustness of the miniature IDP transducers which shows better nonlinearity, sensitivity and reproducibility.
Subjects
Intradiscal pressure
Pressure measurement
Needle transducer
Standard procedure
Type
thesis
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