Christopher Wottawa

Pilot testing of a haptic feedback rehabilitation system on a lower-limb amputee

Lower-limb amputation, whether by trauma or complication of another condition, affects more than 800,000 people in the United States alone. These patient groups typically suffer from decreased mobility and an increased incidence of injury due to fall, even with the application of prosthetic limbs. A haptic feedback system prototype was previously developed to provide augmentative sensory information to patients suffering from total or attenuated lower-limb sensory loss. By providing tactile cues to the user based on plantar pressure distributions, it is hoped that this system can improve rehabilitation and functional outcomes following lower-limb injury. This paper presents an updated system that was fitted to the residual limb of a below-knee amputee, as well as a pilot study using the device. The pilot study demonstrated that the amputee could accurately perceive various tactile stimuli with high accuracy (≫ 87.5%), therefore indicating that the approach is feasible.

Fabrication of a thin-film capacitive force sensor array for tactile feedback in robotic surgery

Although surgical robotic systems provide several advantages over conventional minimally invasive techniques, they are limited by a lack of tactile feedback. Recent research efforts have successfully integrated tactile feedback components onto surgical robotic systems, and have shown significant improvement to surgical control during in vitro experiments. The primary barrier to the adoption of tactile feedback in clinical use is the unavailability of suitable force sensing technologies. This paper describes the design and fabrication of a thin-film capacitive force sensor array that is intended for integration with tactile feedback systems. This capacitive force sensing technology could provide precise, high-sensitivity, real-time responses to both static and dynamic loads. Capacitive force sensors were designed to operate with optimal sensitivity and dynamic range in the range of forces typical in minimally invasive surgery (0 - 40 N). Initial results validate the fabrication of these capacitive force-sensing arrays. We report 16.3 pF and 146 pF for 1-mm2 and 9-mm2 capacitive areas, respectively, whose values are within 3% of theoretical predictions.

Remote tactile sensing glove-based system

A complete glove-based master-slave tactile feedback system was developed to provide users with a remote sense of touch. The system features a force-sensing master glove with piezoresistive force sensors mounted at each finger tip, and a pressure-transmitting slave glove with silicone-based pneumatically controlled balloon actuators, mounted at each finger tip on another hand. A control system translates forces detected on the master glove, either worn by a user or mounted on a robotic hand, to discrete pressure levels at the fingers of another user. System tests demonstrated that users could accurately identify the correct finger and detect three simultaneous finger stimuli with 99.3% and 90.2% accuracy, respectively, when the subjects were located in separate rooms. The glove-based tactile feedback system may have application to virtual reality, rehabilitation, remote surgery, medical simulation, robotic assembly, and military robotics.

Torso-based tactile feedback system for patients with balance disorders

A tactile feedback vest was developed to provide sensory information to patients with balance disorders. The system was designed to detect levels of imbalance that are imperceptible to patients with balance deficit, and to provide intuitive and appreciable sensory feedback that allows for rapid balance correction. Polydimethylsiloxane (PDMS) based pneumatic actuators were clustered on the ventral, dorsal, left and right surfaces of the tactile vest to provide multi-directional sensory feedback. Two biaxial accelerometers were mounted near the shoulder to measure linear and angular acceleration of the upper torso, and a system controller that regulates communication between the sensors and actuators was developed. Actuator deflection was characterized to optimize tactile feedback. Average deflections of 2.6 mm and 7.1 mm were recorded with input pressures of 1.6 psi and 4.0 psi, respectively. In future studies, human perceptual testing will be performed to optimize the system for clinical use.

Tactile Feedback in Surgical Robotics

While commercial surgical robotic systems have provided improvements to minimally invasive surgery, such as 3D stereoscopic visualization, improved range of motion, and increased precision, they have been designed with only limited haptic feedback. A number of robotic surgery systems are currently under development with integrated kinesthetic feedback systems, providing a sense of resistance to the hands or arms of the user. However, the application of tactile feedback systems has been limited to date. The challenges and potential benefits associated with the development of tactile feedback systems to surgical robotics are discussed. A tactile feedback system, featuring piezoresistive force sensors and pneumatic silicone-based balloon actuators, is presented. Initial tests with the system mounted on a commercial robotic surgical system have indicated that tactile feedback may potentially reduce grip forces applied to tissues and sutures during robotic surgery, while also providing high spatial and tactile resolution.

Laparoscopic grasper with an integrated tactile feedback system

Minimally invasive laparoscopic surgery offers advantages over open procedures, such as improved recovery time, decreased trauma, and decreased hospital expenses. One drawback to laparoscopic surgery is that tactile feedback provided to the hands of the surgeon is attenuated. Additional tactile feedback may allow surgeons to better control grip force and better identify tissue characteristics, potentially decreasing the learning curve associated with laparoscopic surgery. A tactile feedback system has been developed and integrated into a modified laparoscopic grasper, allowing the forces applied at the grasper tips to be felt by the surgeons hands. Piezoresistive sensors transmit force data to a microcontroller, which then controls a solenoid valve-based pneumatic system. Feedback is provided using silicone-based balloon actuators, which inflate to apply pressure to the surgeons hand. The actuators are flush with the handles, such that they do not hinder movements during surgical task performance. Preliminary tests have shown successful operation of the system with latency less than 50 ms, high actuation pressures (15 PSI), and high perceptual accuracy of the balloon-based stimuli (≫ 90%).

Minimization of patient misidentification through proximity-based medical record retrieval

Patient misidentification in point-of-care environments can cause serious errors in medication dispersal, blood transfusions, and procedures, leading to patient injury or death. Pre- and post-operative care locations are especially susceptible to these types of errors due to the high volume of patients, as well as the short turnaround time. Proximity-based, on-demand pairing of patients to records may potentially save time for physicians and nurses, as well as reduce the incidence of error in medication and procedure administration. A cost-effective system has been developed that wirelessly pairs patients with their medical records, and allows confirmation through visual feedback. Patients wear an embedded device that electronically stores critical information such as hospital ID, blood type, and allergies. Base stations, or nearby computers, provide on-demand color-coded lists of patients within a limited range, allowing point-of-care providers quick and accurate access to patient information.