Proximity Sensation Enhances Robotic Surgery Fine Finger Control

Transcutaneous pulsed electrical stimulation applied to the fingertips of robotic surgery teleoperators can provide an accurate perception of distance to contact, according to a new study.

Using a system developed at Texas A&M University (TAMU; College Station, TX, USA), the proximity sensations are delivered by passing different frequencies of electrical currents onto the fingertips via gloves fitted with stimulation probes. The researchers then trained users to associate the pulsation frequency as inversely proportional to distance to target, so that an increase in pulsations provided an accurate perception of contact distance. If a teleoperator was sensitive to a wider range of frequencies, smaller steps were used in order to maximize accuracy.

They then compared if receiving the proximity stimulation, in addition to visual feedback information about closing distance displayed on surgical monitors, could provide a better solution for estimating contact proximity than those who received visual information alone. The found that the proximity data delivered through the mild electrical stimulation was about three times more effective than the visual information alone. Users receiving electrical pulses could also lower their force of contact by around 70%. The study was published in the January 2020 issue of Scientific Reports.

“One of the challenges with robotic fingers is ensuring that they can be controlled precisely enough to softly land on biological tissue,” said senior author Hangue Park, PhD, of the department of electrical and computer engineering. “With our design, surgeons will be able to get an intuitive sense of how far their robotic fingers are from contact, information they can then use to touch fragile structures with just the right amount of force.”

“This novel approach has the potential to significantly increase maneuverability during surgery, while minimizing risks of unintended tissue damage,” concluded Dr. Park. “When our technique is ready for use in surgical settings, physicians will be able to intuitively know how far their robotic fingers are from underlying structures, which means that they can keep their active focus on optimizing the surgical outcome of their patients.”

Although visual feedback plays a major role in delivering sensory information during human motor control with its incomparable information transfer capability, peripheral sensory feedback effectively compensates for limitations of visual feedback. For example, tactile feedback provides texture and pressure during the contact and interact phases; and proprioception at the muscles proximal to the fingertip provides useful spatial information, especially during the approach phase.

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