12 Preliminary Characterization of a Plastic Piezoelectric Motor Stator Using High-Speed Digital Holographic Interferometry 93 data from six trials with one plastic stator operating at 6.788 kHz and 160 V are shown in Fig. 12.6, and the overall shapes are similar to a Pearson correlation coefficient ranging from 0.8122 to 0.9615. The upper and lower red dashed lines indicate the envelope from effective data with outlier displacements removed. The stator is considered settled when the sine amplitude stops increasing. As observed, the stator settled to a steady state at, approximately, the 200th frame, which implies an estimated settling time of the amplitude of the envelop of the out-of-plane motion of 2.986 ms. Notice that since this work was operated at low excitation frequency and voltage, the displacement is much lower than expectation. By setting up higher excitation voltage to the crystal electrodes, the displacement will be larger compared to the data presented above. 12.4 Conclusion and Future Work MRI compatible surgical robots are a promising avenue in the treatment of deep brain tumors. Motors minimizing the amount of conductive material may be needed to improve their compatibility with the scanner. An initial prototype of a plastic stator for a rotary piezoelectric actuator was imaged using a high-speed digital holography (HDH) system and compared to the metal stator of a commercially available motor. The ability of the stator to excite and sustain a stable mode points toward the possibility of using a plastic stator in the construction of a more MRI conditional piezoelectric motor. However, some considerations are still required and are suggested for future work. Plastic is a poor conductor of heat, which may lead to overheating and damage of the bonded piezoelectric ring. The heating of the stator during operation should be quantified and other nonmetal materials, such as Macor glass ceramic, should also be evaluated. We have validated operation in the second mode. More commonly, piezoelectric motors operate in the fifth or sixth mode. The acquisition rate of the camera should be increased to enable measuring the motor with these higher frequency and voltage modes, which usually operate at frequencies from 30 kHz to 60 kHz requiring camera acquisition rates on the order of 600 k fps or higher. Determining a relationship between stator geometry and settling time is also left unexplored. Understanding these points may be beneficial prior to constructing a full motor assembly. Acknowledgment Funding provided by the National Institutes of Health (NIH) under the National Cancer Institute (NCI) (Grant No. R01CA166379). References 1. Siegel, R.L., Miller, K.D., Jemal, A.: Cancer statistics, 2019. CA Cancer J. Clin. 69, 7–34 (2019) 2. 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