A Piezoelectric Tactile Sensor for Tissue Stiffness Detection with Arbitrary Contact Angle

Abstract

In this paper, a piezoelectric tactile sensor for detecting tissue stiffness in robot-assisted minimally invasive surgery (RMIS) is proposed. It can detect the stiffness not only when the probe is normal to the tissue surface, but also when there is a contact angle between the probe and normal direction. It solves the problem that existing sensors can only detect in the normal direction to ensure accuracy when the degree of freedom (DOF) of surgical instruments is limited. The proposed senor can distinguish samples with different stiffness and recognize lump from normal tissue effectively when the contact angle varies within [0°, 45°]. These are achieved by establishing a new detection model and sensor optimization. It deduces the influence of contact angle on stiffness detection by sensor parameters design and optimization. The detection performance of the sensor is confirmed by simulation and experiment. Five samples with different stiffness (including lump and normal samples with close stiffness) are used. Through blind recognition test in simulation, the recognition rate is 100% when the contact angle is randomly selected within 30°, 94.1% within 45°, which is 38.7% higher than the unoptimized sensor. Through blind classification test and automatic k-means clustering in experiment, the correct rate is 92% when the contact angle is randomly selected within 45°. We can get the proposed sensor can easily recognize samples with different stiffness with high accuracy which has broad application prospects in the medical field.

A review of tactile sensors used in surgical robots

“…The rate of accuracy is 92% for stiffness detection of random selected contact angle with 45 degree, and for samples with 30 degree, the accuracy rate is 100%. This improved the situation that past piezoelectric sensors could only measure the stiffness vertically when the degree of freedom is limited, but it is only available for certain range of angle due to accuracy [8].…”

Piezoelectric approaches to organic polymeric materials

“…[20][21][22][23][24] In the medical field, they are used in surgical instruments and ultrasound machines for medical imaging. [25][26][27][28][29][30] Piezoelectric materials can be classified into three general categories, namely ceramics, bulk piezoelectric polymers, and composites. 31,32 Ceramics are the most widely used owing to their exceptionally high piezoelectric coefficients (e.g.…”

Design and Characterization of Three-Axis High-Range Inductive Tactile Force Sensor Utilizing Magnetorheological Elastomer for Robotic Surgical Applications

“…Tactile sensors can play a major role in providing force feedback from surgical instruments to the surgeon. The working of tactile force sensors, presented in the literature, is based on different transduction mechanisms including capacitive [10], [11], piezoresistive [12], [13], piezoelectric [14], [15], magnetic [16], [17], and optical [18], [19]. The capacitive tactile force sensors allow to achieve high sensitivity and resolution but are easily susceptible to parasitic capacitance and noise from nearby equipment and materials.…”