MIS has attracted more and more attention due to its advantages over conventional surgery. However, tactile information ordinarily available during conventional surgery is still yet to be effectively integrated into robot-assisted MIS.

The research team proposed a highly sensitive Fiber Bragg Grating (FBG) sensing solution for minimally invasive surgical tissue palpation. Unlike previous capacitive sensing solutions, fiber optic sensors are compatible with intraoperative magnetic resonance imaging (MRI) systems.  

FBGs have been widely used in sensing field because of their high sensitivity, low signal loss, and no influence from electromagnetic interference. But its central wavelength shift is cross-impacted by the temperature and strain, so the temperature compensation is an important criterion needed to accurately map the relationship between an applied force and the corresponding central wavelength shift.  

In this study, this sensor includes two FBGs closely arranged in the sensor structure to detect palpation force while minimizing the interference of temperature and noise.

The experimental results showed that the designed force sensor could measure force values in a range of 1N with an average relative error less than 2% of full scale, and the average error value of the designed sensor after temperature compensation was 0.8 mN.  

Furthermore, the researchers conducted tissue palpation experiments on pig liver organs to verify the effectiveness and applicability of the proposed sensor in MIS. They found that the sensor could be accurately used in tissue palpation and lump localization by searching at varying degrees of indentation depth during MIS. 

The structure of the double grating decouples the temperature effect and improves the force sensing accuracy of the sensor, thus increasing the accuracy and safety of tissue palpation surgery.