Session: 05-12-02: Robotics, Rehabilitation - II

Paper Number: 95988

95988 - A Microrobot With an Attached Micro-Force Sensor for Natural Orifice Access to the Bladder Interior Wall 

Understanding and characterizing the elastic properties of bladder tissue provides a critical step towards understanding diseases or dysfunction inducing Urinary Incontinent (UI) and/or providing better patient care. However, current approaches such as cystometry or elastography used to assess the elasticity of the bladder have a lot of variability in that they do not provide measurements from direct contact between a sensor and the bladder interior wall for localized tissue characterization. The promising possibilities of robotic endoscopes currently available for in-vivo diagnostic surgery suffer from limitations that include mechanical design, size constraints due to accessibility channels, and difficulty in spatial orientation of the endoscope end-effector due to articulation (particularly for those with flexible architectures). For instance, transurethral robotic interventions are constrained by the geometry of the urethra and the bladder when reaching a proposed target while considering patient comfort. Likewise, localized real-time measurements during such interventions in the human bladder are crucial for patient care.  

As a result, in this research, we will present the conceptual design of a 3.5 mm outside diameter (OD) cable-driven hyper-redundant robotic manipulator to address geometry constraints associated with the diameter of a diagnostic instrument that could host a micro-force sensor at the tip for application in transurethral palpation of any targeted area of the bladder interior wall tissue. The design and prototyping of a strain gauge based micro-force sensor with a safety factor (>3) and a load bearing capacity of at least 1.2N to acquire palpation measurements will also be presented.  The proposed manipulator is a 6-degree-of-freedom (DOF) hyper-redundant articulated manipulator with 10 joints (5 passive and 5 active). The hyper-redundant manipulator has the ability to orient the end-effector attached force sensor perpendicular to the bladder wall anywhere in the interior of the bladder.  The last 5-passive joints allow the manipulator to mainly reach and contribute to the orientation in the interior of the bladder. These joints are constructed from snap joints at the ends of vertebrae links. The vertebrae joints are actuated using flexion and extension tendons routed from the base of the robot to the end of the distal vertebra. The joint limit constraints and associated reasons for them will be defined and discussed. The kinematic motion analysis based on the Jacobian formulation will be presented considering joint limits and pose requirements relative to the bladder interior wall for select locations to demonstrate the ability of the hyper redundant concept to attain a desired pose at any point in the interior of the bladder. A study of the optimal tendon routes will be presented to evaluate the behavior of the robot as well as the minimum energy cost required to operate the robot. Furthermore, finite element analysis to identify the design parameters of the micro-force sensor with an aim to maximize the sensed strain will be discussed. Using 3D printing technologies, initial prototyped vertebrae and micro-force sensor will also be presented and discussed. Preliminary sensor characterization experimentation to evaluate the behavior of the sensor as a function of applied load will be presented. A testbed developed and interfaced with and controlled by LabVIEW is used to evaluate performance characteristics (sensitivity, resolution, accuracy) of a working prototype of the sensor under controlled strain rates and indentation depth while interrogating viscoelastic materials ex-vivo. The micro-force sensor experimental data will be fit to a mathematical model to obtain viscoelastic material properties which could be used to identify the disease state of tissue.  The proposed manipulator and force sensor system will be able to quantitatively evaluate localized biomechanical properties of the bladder interior wall tissue as a means towards improving treatment and better patient care. 

Presenting Author: Panos Shiakolas University of Texas at Arlington

Presenting Author Biography: P. S. SHIAKOLAS received the Higher National Diploma degree from the Higher Technical Institute, Nicosia, Cyprus, in 1982, the B.S. and M.S. degrees from The University of Texas at Austin, in 1986 and 1988, respectively, and the Ph.D. degree from The University of Texas at Arlington (UTA), in 1992, all in mechanical engineering in the areas of robotics and computer aided design. From 1993 to 1996, he worked as a Faculty-Research Associate with UTA. He joined the UTA Faculty as an Assistant Professor, in 1996, where he currently serves as a Tenured Associate Professor for mechanical and aerospace engineering. He is also the Director of the MARS Laboratory, UTA. His research interests include the general areas of robotics, manufacturing, microsystems, automation, and controls as they apply to the betterment of society currently focusing in the medical/biomedical fields. He has a passion for engineering education, and he has developed educational testbeds and routinely uses hardware testbeds to demonstrate concepts in his courses in the areas of robotics, automation, and controls.

Authors:

Samson Adejokun University of Texas, Arlington
Shashank Kumat University of Texas at Arlington
Panos Shiakolas University of Texas at Arlington