Abstract
This article introduces a soft and stretchable sensor composed of silicone rubber integrating a conductive liquid-filled channel with a biocompatible sodium chloride (NaCl) solution and novel stretchable gold sputtered electrodes to facilitate the biocompatibility of the sensor. By stretching the sensor, the cross section of the channel deforms, thus leading to a change in electrical resistance. The functionalities of the sensor have been validated experimentally: changes in electrical resistance are measured as a function of the applied strain. The experimentally measured values match theoretical predictions, showing relatively low hysteresis. A preliminary assessment on the proposed sensor prototype shows good results with a maximum tested strain of 64%. The design optimization of the saline solution, the electrodes, and the algebraic approximations derived for integrating the sensors in a flexible manipulator for surgery has been discussed. The contribution of this article is the introduction of the biocompatible and stretchable gold sputtered electrodes integrated with the NaCl-filled channel rubber as a fully biocompatible solution for measuring deformations in soft and stretchable medical instruments.
Highlights
Recent years have seen a growing interest in the development of continuum-like and soft robots that can bend, extend, and contract at any point along their length
Some examples are a soft robotic arm modeled on the octopus[2] and a multigait soft walker powered by compressed air.3A key use of soft robotics can be found in medical applications, where attention has been currently focused on minimizing the invasiveness of existing minimally invasive surgery (MIS) approaches
Several sensing strategies for MIS have been proposed over the past years,[7,8,9,10] Ideally, the entire robotic structure should safely move with contact and bend detection and the embedded sensors should not interfere with the overall motion, remaining functional even when highly deformed.[11]
Summary
Recent years have seen a growing interest in the development of continuum-like and soft robots that can bend, extend, and contract at any point along their length. The STIFF-FLOP arm takes inspiration from biological manipulation and it is fabricated from soft structures showing advanced manipulation capabilities for surgical applications, with multiple degrees of freedom, bending, and ability of elongating and squeezing.[4] These soft and flexible devices introduce new challenges because sensing and controlling the shape and motion of continuum robots are more complicated due to their structural flexibility[5]; the contact region can be quite wide and is not limited to the end effector tip as for rigid robots.[6]. Several sensing strategies for MIS have been proposed over the past years,[7,8,9,10] Ideally, the entire robotic structure should safely move with contact and bend detection and the embedded sensors should not interfere with the overall motion, remaining functional even when highly deformed.[11] For these reasons, the use of small, soft, and stretchable sensors becomes necessary, especially inside the human body. The possible future implementation of the sensor inside a surgical manipulator will be discussed
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