A FaceShear Mode Piezoelectric Array Sensor for Elasticity and Force Measurement We present the development of a 6 xc3x97 6 piezoelectric array sensor for measuring elasticity and force. The proposed sensor employs an impedance measurement technique, sensing the acoustic load impedance of a target by measuring the electrical impedance shift of faceshear mode PMNxe2x80x93PT (lead magnesium niobatexe2x80x93lead titanate) single crystal elements. Among various modes of PMNxe2x80x93PT single crystals, the faceshear mode was selected due to its especially high sensitivity to acoustic loads. To verify the elasticity sensing performance, gelatin samples with different elastic moduli were prepared and tested. For the force measurement test, different magnitudes of force were loaded to the sensing layer whose acoustic impedance was varied with applied forces. From the experimental results, the fabricated sensor showed an elastic stiffness sensitivity of 23.52 OhmMPa with a resolution of 4.25 kPa and contact force sensitivity of 19.27 OhmN with a resolution of 5.19 mN. In addition, the mapping experiment of elasticity and force using the sensor array was successfully demonstrated.

Estimating and Localizing External Forces Applied on Flexible Instruments by Shape Sensing Force sensing is highly desirable in medical applications showing great potential to reduce tissue damage and enhance manipulation safety. Embedding force sensors in medical devices is however challenging and costly. Provided that the medical device is long, slender and largely compliant, we show in this paper that it is possible to estimate multiple loads along the length of the flexible instrument using a Cosseratrod model and Fiber Bragg Grating sensors, which allows simultaneous shape and force sensing. We perform experiments that illustrate the feasibility of using this method to locate multiple contact forces along the instrument, and to estimate the magnitudes of the forces that are applied along the length of the instrument. Results show that onedirectional force magnitude and location can be estimated with an average error of 6.3% and 5.4 mm (3.0% of rod length), respectively. In the worst case, the error for magnitude and location can go up to 22.6% and 13.9 mm (7.7% of rod length), respectively. For twodirectional forces, results show an average error of 9.8% for magnitude and 6.4 mm (3.6% of rod length) for the location. The errors on magnitude and location do not exceed 27.4% and 17.4 mm (9.7% of rod length), respectively.