A Distributed-Deflection Sensor With a Built-In Probe for Conformal Mechanical Measurements of Costal Cartilage at Its Exterior Surface

Abstract

In this paper, a distributed-deflection sensor with a built-in probe is proposed to achieve conformal mechanical measurements of costal cartilage (CC) at its exterior surface. The sensor entails a rectangular sensing-plate integrated with a $5 \times 1$ transducer array with 0.75 mm spatial resolution underneath and a built-in probe of $0.5~{\mathrm{ mm}}\times 5~{\mathrm{ mm}}\times 3~{\mathrm{ mm}}$ above. By pressing the sensor against the exterior surface of a CC tissue with a pre-defined indentation depth pattern, the sensor conforms to the curved tissue surface via the built-in probe first, and then the mechanical properties of the tissue translate to the spatially distributed deflection in the sensor and register as resistance changes by the transducer array. One human Pectus Carinatum (PC) CC sample is measured using the sensor without a built-in probe, and two human PC samples are measured using the sensor with a built-in probe. The comparison in measured results among the three samples validates the capability of the sensor with a built-in probe for conformity to a curved tissue surface in measurements. Based on the recorded relation of average sensor deflection to indentation depth of the two samples measured using the sensor with a built-in probe, the tissue instant indentation modulus and normalized relaxation amount of the two samples are derived and found to vary significantly among the anterior/posterior surfaces and superior/inferior borders at the same position of each sample.