A grasping forceps with a triaxial MEMS tactile sensor for quantification of stresses on organs

Pneumatically driven surgical forceps displaying a magnified grasping torque

BACKGROUND

Sensing the grasping force and displaying the force for the operator are important for safe operation in robot-assisted surgery. Although robotic forceps that senses the force by force sensors or driving torque of electric motors is proposed, the force sensors and the motors have some problems such as increase in weight and difficulty of the sterilization.

METHOD

We developed a pneumatically driven robotic forceps that estimates the grasping torque and display the magnified torque for the operator. The robotic forceps has a master device and a slave robot, and they are integrated. In the slave side, the grasping torque is estimated by the pressure change in the pneumatic cylinder. A pneumatic bellows display the torque through a linkage.

RESULTS

We confirmed that the slave robot follows the motion of the master, and the grasping torque is estimated in the accuracy of 7 mNm and is magnified and displayed for the operator.

CONCLUSIONS

The pneumatically driven robotic forceps has the capability in the estimation of the grasping torque and display of the torque. Regarding future work, the usability and fatigues of the surgeons must be evaluated.

Grasper having tactile sensing function using acoustic reflection for laparoscopic surgery

PURPOSE

In current minimally invasive surgery techniques, the tactile information available to the surgeon is limited. Improving tactile sensation could enhance the operability of surgical instruments. Considering surgical applications, requirements such as having electrical safety, a simple structure, and sterilization capability should be considered. The current study sought to develop a grasper that can measure grasping force at the tip, based on a previously proposed tactile sensing method using acoustic reflection. This method can satisfy the requirements for surgical applications because it has no electrical element within the part that is inserted into the patient's body.

METHODS

We integrated our acoustic tactile sensing method into a conventional grasping forceps instrument. We designed the instrument so that acoustic cavities within a grasping arm and a fork sleeve were connected by a small cavity in a pivoting joint. In this design, when the angle between the two grasping arms changes during grasping, the total length and local curvature of the acoustic cavity remain unchanged. Thus, the grasping force can be measured regardless of the orientation of the grasping arm.

RESULTS

We developed a prototype sensorized grasper based on our proposed design. Fundamental tests revealed that sensor output increased with increasing contact force applied to the grasping arm, and the angle of the grasping arm did not significantly affect the sensor output. Moreover, the results of a grasping test, in which objects with different softness characteristics were held by the grasper, revealed that the grasping force could be appropriately adjusted to handle different objects on the basis of sensor output.

CONCLUSIONS

Experimental results demonstrated that the prototype grasper can measure grasping force, enabling safe and stable grasping.

A CMOS micromachined capacitive tactile sensor with integrated readout circuits and compensation of process variations

This paper presents a capacitive tactile sensor fabricated in a standard CMOS process. Both of the sensor and readout circuits are integrated on a single chip by a TSMC 0.35 μm CMOS MEMS technology. In order to improve the sensitivity, a T-shaped protrusion is proposed and implemented. This sensor comprises the metal layer and the dielectric layer without extra thin film deposition, and can be completed with few post-processing steps. By a nano-indenter, the measured spring constant of the T-shaped structure is 2.19 kNewton/m. Fully differential correlated double sampling capacitor-to-voltage converter (CDS-CVC) and reference capacitor correction are utilized to compensate process variations and improve the accuracy of the readout circuits. The measured displacement-to-voltage transductance is 7.15 mV/nm, and the sensitivity is 3.26 mV/μNewton. The overall power dissipation is 132.8 μW.