This paper studies the viability of using a class of phase-changing materials for the design of controlled variable stiffness robotic joints which enable the design of robots that can operate in confined spaces. In such environments, robots need to be able to navigate in proximity or while in contact with their environment to reach one or more manipulated target. Joints with controllable stiffness can substantially enhance functionality of this class of robots where relatively higher joint stiffness is required to support the robot weight against gravity and low stiffness is desired when operating in complex or delicate environments. The research work presented in this paper focuses on examining thermorheological fluids (TRF) to design and manufacture thermally controlled variable stiffness joints. Two phase-changing materials are considered in the study: low-melting-point solder and hot-melt adhesive. Both materials are embedded in a custom designed joint fabricated using 3D printing and silicone casting. Joint stiffness was investigated with both materials and reported here. The results shows that the proposed variable stiffness joints with TRF achieve wide ranges of load-deflection ratio varying between 0.05 N/mm (when thermally activated) to about 10 N/mm (in bonding state). On average, the joint can withstand 20 times its total weight when in the bonding state. Design challenges and durability of TRF-based joints are discussed.

The recent global pandemic has posed unprecedented challenges to public health systems and has highlighted the critical need for effective, contactless disinfection strategies in shared environments. This study investigates the use of autonomous robotics to enhance disinfection efficiency and safety in public spaces through the development of a custom-built mobile spraying platform. The proposed robotic system is equipped with an integrated 3D object pose estimation framework that fuses RGB-based object detection with point cloud segmentation to accurately identify and localize high-contact surfaces. To facilitate autonomous operation, both local and global motion planning algorithms are implemented, enabling the robot to navigate complex environments and execute disinfection tasks with minimal human intervention. Experimental results demonstrate the feasibility of the proposed disinfection robotic system.