IEEE TRANSACTIONS ON BIOMEDICAL ENGINEERING, VOL. 55, NO. 11, NOVEMBER 2008 2593 Optimization of a Pneumatic Balloon Tactile Display for Robot-Assisted Surgery Based on Human Perception Chih-Hung King*, Martin O. Culjat, Miguel L. Franco, James W. Bisley, Erik Dutson, and Warren S. Grundfest Abstract—Robot-assisted surgery is characterized by a total loss of haptic feedback, requiring surgeons to rely solely on visual cues. A compact, flexible, and lightweight pneumatic balloon tactile dis- play has been developed suitable for mounting on robotic sur- gical master controls. The tactile display consists of a molded polydimethylsiloxane substrate with cylindrical channels and a spin-coated silicone film that forms the array of balloons. Human perceptual studies were conducted to determine the optimal di- ameter, spatial resolution, and temporal resolution of the balloon actuator design. A balloon diameter of 3.0 mm provided the high- est average accuracy (≥95%) while offering five detectable infla- tion levels. Spatial accuracy in a two-actuator discrimination task reached 100% with 1.5 mm edge-to-edge spacing, and the accuracy of determining the order of two successive stimuli was greater than 90% when the time separation was 100 ms. Design optimization based on the results from this study enables the described tactile display to provide the effective tactile feedback that is otherwise unavailable during robotic surgery. Index Terms—Haptic feedback, haptic perception, robot tactile systems. I. INTRODUCTION R OBOTIC systems with master–slave control were intro- duced to surgery in the early 1990s, providing advanced features such as stereoscopic vision, tremor reduction, addi- tional degrees of freedom, increased precision, and teleopera- tion capabilities [1]–[5]. Currently, the only such robotic surgi- cal system approved by the U.S. Food and Drug Administration for use in abdominal, pelvic, and cardiothoracic surgery is the da Vinci Surgical System (Intuitive Surgical, Inc., Sunnyvale, CA). The da Vinci system features a control console that allows Manuscript received August 13, 2007; revised April 15, 2008. First published June 10, 2008; current version published October 31, 2008. This work was sup- ported in part by the Telemedicine and Advanced Technology Research Center (TATRC)/Department of Defense under Award W81XWH-05-2-0024. The work of J. W. Bisley was supported by the Alfred P. Sloan Research Fellowship and a Klingenstein Fellowship Award. Asterisk indicates corresponding author. *C. H. King is with the Department of Biomedical Engineering, University of California, Los Angeles (UCLA), Los Angeles, CA 90095 USA, and also with the Center for Advanced Surgical and Interventional Technology (CASIT), Los Angeles, CA 90095-1600 USA (e-mail: aaking@ucla.edu). M. O. Culjat and E. Dutson are with the Department of Surgery, University of California, Los Angeles (UCLA) School of Medicine, Los Angeles, CA 90095 USA, and also with the Center for Advanced Surgical and Interventional Tech- nology (CASIT), Los Angeles, CA 90095-1600 USA. M. L. Franco is with the University of California, Los Angeles (UCLA), Los Angeles, CA 90095 USA, and also with the Center for Advanced Surgical and Interventional Technology (CASIT), Los Angeles, CA 90095-1600 USA. J. W. Bisley is with David Geffen School of Medicine, University of California, Los Angeles (UCLA), Los Angeles, CA 90095 USA. W. S. Grundfest is with the University of California, Los Angeles (UCLA), Los Angeles, CA 90095 USA. Digital Object Identifier 10.1109/TBME.2008.2001137 a surgeon to manipulate robotic arms remotely and a robotic ap- paratus with three arms (or four arms) that hold a stereoscopic endoscope and detachable laparoscopic surgical tools. The sur- geon controls the arms by manipulating two master controls with the index finger and thumb of both hands with each finger inserted into a Velcro support strap. A major limitation of robotic surgery is the complete absence of haptic feedback [6], [7]. During robotic surgery, surgeons are completely isolated from the patient and rely solely on visual cues. Previous studies have suggested that force feedback may be beneficial to robotic surgery [8]–[11]. Kitagawa et al. [12] showed that the force feedback may facilitate the performance of surgical knot tying using sensory substitution (visual and audio cues) in surgical robots. However, the majority of previous research has focused on force (kinesthetic) rather than tactile (cutaneous) feedback. The addition of a tactile display, or tactile feedback actuator array, to the master controls, when integrated with a tactile sensor array mounted onto the tips of robotic graspers, may enable surgeons to “feel” tissue characteristics, appropriately tension sutures, identify pathologic conditions, and enable expansion of robotic minimally invasive surgery (MIS) to other surgical procedures. The size of the finger pad and limited mounting space on the robotic surgical master controls require a tactile display that is compact, flexible, and lightweight. In the case of the da Vinci Surgical System, the available mounting area is approximately 1.0 cm × 1.8 cm. Various tactile display technologies, including electromagnetic, electrocutaneous, electrostatic, motor, piezo- electric, rheological fluid, and shape-memory alloy (SMA) ac- tuators, have previously been explored [13]–[19]. Pneumatic tactile actuators are capable of producing high displacement and large output force [20]; however, those that have been developed are not practical for surgical robotics due to bulky size, awkward geometries for mounting, or slow dynamic response [21]–[24]. We have developed a modular and scalable pneumatic actua- tor designed to provide haptic feedback to the fingers using an array of balloons formed from a spin-coated silicone film placed over a molded substrate. This design incorporates the advantages of low mass, compact size, large force output, and deflection, and can be integrated with the master controls of surgical robotic systems. The elastic balloon films have the ability to conform to the shape of the fingers, allowing uniform distribution of force. The balloon actuators are designed to provide haptic input into the human sensory system by stimulating the mechanoreceptors through skin deformation [25]. Previous mechanical charac- terization tests on our balloon actuators have demonstrated a 0018-9294/$25.00 © 2008 IEEE Authorized licensed use limited to: UNIVERSIDAD POLITECNICA DE VALENCIA. Downloaded on May 04,2010 at 21:55:40 UTC from IEEE Xplore. Restrictions apply.