Needle insertion into soft tissue: a survey.

Any device which senses information such as shape, texture, softness, temperature, vibration or shear and normal forces, by physical contact or touch, can be termed a tactile sensor. The importance of tactile sensor technology was recognized in the 1980s, along with a realization of the importance of computers and robotics. Despite this awareness, tactile sensors failed to be strongly adopted in industrial or consumer markets. In this paper, previous expectations of tactile sensors have been reviewed and the reasons for their failure to meet these expectations are discussed. The evolution of different tactile transduction principles, state of art designs and fabrication methods, and their pros and cons, are analyzed. From current development trends, new application areas for tactile sensors have been proposed. Literature from the last few decades has been revisited, and areas which are not appropriate for the use of tactile sensors have been identified. Similarly, the challenges that this technology needs to overcome in order to find its place in the market have been highlighted.

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A review of tactile sensing technologies with applications in biomedical engineering

Because of their continuous and natural motion, fluidically powered soft actuators have shown potential in a range of robotic applications, including prosthetics and orthotics. Despite these advantages, robots using these actuators require stretchable sensors that can be embedded in their bodies for sophisticated functions. Presently, stretchable sensors usually rely on the electrical properties of materials and composites for measuring a signal; many of these sensors suffer from hysteresis, fabrication complexity, chemical safety and environmental instability, and material incompatibility with soft actuators. Many of these issues are solved if the optical properties of materials are used for signal transduction. We report the use of stretchable optical waveguides for strain sensing in a prosthetic hand. These optoelectronic strain sensors are easy to fabricate, are chemically inert, and demonstrate low hysteresis and high precision in their output signals. As a demonstration of their potential, the photonic strain sensors were used as curvature, elongation, and force sensors integrated into a fiber-reinforced soft prosthetic hand. The optoelectronically innervated prosthetic hand was used to conduct various active sensation experiments inspired by the capabilities of a real hand. Our final demonstration used the prosthesis to feel the shape and softness of three tomatoes and select the ripe one.

Optoelectronically innervated soft prosthetic hand via stretchable optical waveguides

Purpose of Review
Robot-assisted minimally invasive surgery (RMIS) holds great promise for improving the accuracy and dexterity of a surgeon while minimizing trauma to the patient. However, widespread clinical success with RMIS has been marginal. It is hypothesized that the lack of haptic (force and tactile) feedback presented to the surgeon is a limiting factor. This review explains the technical challenges of creating haptic feedback for robot-assisted surgery and provides recent results that evaluate the effectiveness of haptic feedback in mock surgical tasks.

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Haptic Feedback in Robot-Assisted Minimally Invasive Surgery

Haptic perception plays a very important role in surgery. It enables the surgeon to feel organic tissue hardness, measure tissue properties, evaluate anatomical structures, and allows him/her to commit appropriate force control actions for safe tissue manipulation. However, in minimally invasive surgery, the surgeon's ability of perceiving valuable haptic information through surgical instruments is severely impaired. Performing the surgery without such sensory information could lead to increase of tissue trauma and vital organic tissue damage. In order to restore the surgeon's perceptual capability, methods of force and tactile sensing have been applied with attempts to develop instruments that can be used to detect tissue contact forces and generate haptic feedback to the surgeon. This paper reviews the state-of-the-art in force and tactile sensing technologies applied in minimally invasive surgery. Several sensing strategies including displacement-based, current-based, pressure-based, resistive-based, capacitive-based, piezoelectric-based, vibration-based, and optical-based sensing are discussed.

State-of-the-Art in Force and Tactile Sensing for Minimally Invasive Surgery

Force feedback is widely assumed to enhance performance in robotic surgery, but its benefits have not yet been systematically assessed. In this study we examine the effects of force feedback on a blunt dissection task. Subjects used a telerobotic system to expose an artery in a synthetic model while viewing the operative site with a video laparoscope. Performance was compared between force feedback gains of 75% and 150% and no force feedback. The absence of force feedback increased the average force magnitude applied to the tissue by at least 50%, and increased the peak force magnitude by at least a factor of 2. The number of errors that damage tissue increased by over a factor 3. The rate and precision of dissection were not significantly enhanced with force feedback. We hypothesize that force feedback is helpful in this blunt dissection task because the artery is stiffer than the surrounding tissue. This mechanical contrast serves to constrain the subjects' hand from commanding inappropriate motions that generate large forces.

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The role of force feedback in surgery: analysis of blunt dissection

A teletaction system uses a tactile display to present the user with information about texture, local shape, and/or local compliance. Current tactile displays are flat and rigid, and require precise machining and assembly of many parts. This paper describes the fabrication and performance of a one-piece pneumatically-actuated tactile display molded from silicone rubber. Tactor spacing is 2.5 mm with 1 mm diameter tactor elements. Tactile display compliance ensures contact between the finger and tactile display at all times. Unlike previous pneumatic tactile displays, there is no chamber leakage and no seal friction. A psychophysics experiment showed that a synthetic grating on the tactile display was perceived as well as a low-pass-filtered real contact.

A compliant tactile display for teletaction

Tactile displays are used to convey small-scale force and shape information to the tip of the finger. In this paper, we present a 6/spl times/6 tactile shape display that uses commercial radio-controlled (RC) servomotors to actuate an array of mechanical pins. The display has a maximum pin deflection of 2 mm along with a resolution of 4 bits. Pin spacing is 2 mm with a pin diameter of 1 mm. The display can accurately represent frequencies up to 25 Hz for small amplitudes and the slew rate is limited at 38 mm/sec for larger amplitudes.

/pdf/a-tactile-shape-display-using-rc-servomotors-24szbhshyz.pdf

A tactile shape display using RC servomotors

Force feedback is widely assumed to enhance performance in robotic surgery, but its benefits have not yet been systematically assessed. In this study we examine the effects of force feedback on a blunt dissection task. Twenty subjects used a telerobotic system to expose an artery in a synthetic model while viewing the operative site with a video laparoscope. Subjects were drawn from a range of surgical backgrounds, from inexperienced to attending surgeons. Performance was compared between three force feedback gains: 0% (no force feedback), 37%, and 75%. The absence of force feedback increased the average force magnitude applied to the tissue by at least 50%, and increased the peak force magnitude by at least 100%. The number of errors that damage tissue increased by over a factor of 3. The rate and precision of dissection were not significantly enhanced with force feedback. These results hold across all levels of previous surgical experience. We hypothesize that force feedback is helpful in this blunt dissection task because the artery is stiffer than the surrounding tissue. This mechanical contrast serves to constrain the subject's hand from commanding inappropriate motions that generate large forces.

/pdf/the-benefit-of-force-feedback-in-surgery-examination-of-o7a8emdros.pdf

The Benefit of Force Feedback in Surgery: Examination of Blunt Dissection

Force feedback has been suggested to provide a number of benefits to surgery. Few studies, however, have addressed the benefit of force feedback in the context of the complexities of true surgical tasks. When information is limited (such as depth information in endoscopically guided tasks), force feedback may provide additional information that improves performance. We investigate a two-handed, six degree of freedom, endoscopically guided, minimally invasive cannulation task (inserting one tube into another tube) to test this hypothesis. We used twelve subjects, six of whom were experienced minimally invasive surgeons. Results suggest that force feedback reduces applied forces for both subject groups, but only the surgically trained group can take advantage of this benefit without a significant increase in trial time. We hypothesize that this training difference is due to the interaction between visual-spatial motor abilities and the information contained in the mechanical interaction forces.

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C.R. Wagner

Papers

The role of force feedback in surgery: analysis of blunt dissection

A compliant tactile display for teletaction

A tactile shape display using RC servomotors

The Benefit of Force Feedback in Surgery: Examination of Blunt Dissection

Force Feedback Benefit Depends on Experience in Multiple Degree of Freedom Robotic Surgery Task