A Microrobot With an Attached Microforce Sensor for Transurethral Access to the Bladder Interior Wall

We present the conceptual design and limited functionality prototype and characterization of a system for application in transurethral palpation of any targeted area of the bladder interior wall tissue consisting of a robotic manipulator and a microforce sensor attached at its tip all less than $3.5 mm$ in diameter. A hyper-redundant ten-joint six degrees-of-freedom (6DOF) manipulator (5DOF rigid and five-joint continuum segments) is presented along with the forward and inverse kinematics analyses based on a Jacobian formulation to prevent configuration singularities. Simulated motion studies demonstrate the ability of the proposed manipulator to attain a desired pose (normal to the tissue) with any area in the bladder including the difficult to reach trigone area. A strain gauge-based microforce sensor is designed using finite element analysis (safety factor > 3), prototyped using additive manufacturing, and characterized. The characterized sensor was used to acquire in vivo measurements to evaluate human palm tissue viscoelastic properties. A single module of the continuum segment is designed and prototyped using additive manufacturing, and used to characterize its tension-bend angle behavior. Finite element analysis is used to improve structurally weak regions of the vertebra. A three-joint four-vertebrae prototype was successfully actuated to reach a bend state using tendons. The developed robot and sensor prototypes demonstrate capabilities of the proposed concept which could be a possible solution to quantitatively evaluate localized biomechanical properties of the bladder tissue to improve treatment and provide better patient care.