Experimental Research on Sensing Characteristics of Adhesive-Encapsulated FBG Under Alcohol-Disinfection Environment

Fiber Bragg grating (FBG) has proven to be the most suitable sensing element for force feedback of surgical robots because of its special advantages such as small size and physical robustness. In current reports, the researchers packaged FBGs in a surgical instrument by attaching them to an external surface or by embedding them into the shaft grooves using an adhesive because the adhesive has good liquidity and operability compared to other packaging methods, such as metal package and glass solder package, and is often not covered due to the strict space requirement of tiny surgical instruments. However, for repeated disinfection, surgical instruments have to be excessively exposed to chemical disinfectants, which may lead to chronic corrosion of the adhesive, thus influencing the sensing characteristics of the integrated FBGs. To address this concern, this paper investigates the sensing characteristics of the adhesive-encapsulated FBG under disinfection environment. We simulated a common disinfection environment using 75% alcohol, in which three adhesive-encapsulated FBGs were soaked for a long term. The sensing performances of FBGs have been tested periodically, and the experimental results demonstrate that the FBGs have good sensing characteristics within first 50 days. However, after 50 days, the sensing performances of the three FBGs worsened gradually, and, finally, the adhesive layers of the three FBGs completely detached from the specimen in the 75th day, 80th day, and 95th day, respectively. We hope the investigation could provide a valuable reference for better application of the FBG in force feedback of surgical robots.