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Ras Labs makes Synthetic Muscle™, which are electroactive polymer (EAP) based materials and actuators that controllably contract and expand at low voltage (1.5 V to 50 V, battery levels), sense pressure (gentle touch to high impact), and attenuate force. Robotic sensing is mainly visual, which is useful up until the point of contact. To understand how an object is being gripped, tactile feedback is needed. By using soft Synthetic Muscle™ based EAP pads as the sensors, immediate feedback was generated at the first point of contact. Because these pads provided a soft, compliant interface, the force applied to the object to be finely controlled. The EAP sensor could also detect a change in pressure location on its surface, making it possible to detect and prevent slippage by then adjusting the grip strength – directional glide provided feedback for the presence of possible slippage to control with a slightly tighter grip, without stutter, due to both the feedback and the softness of the fingertip-like EAP pads themselves. These EAP pads also naturally held the gripped object, improving the gripping quality over rigid grippers without an increase in applied force. EAPs with appropriate coatings and electronics were positioned as pressure sensors in the fingertip regions of robotic grippers. Pressure position and magnitude tests were successful, with sensitivity down to 0.05 N. While we were holding one of our sensors, we noticed what we thought was an electronic artifact, but was the sensor picking up the heartbeat pulse in our fingers. The pressure range is from 0.05 N to about 20 N within the same sensor. The different touch points of the gripper sensed different areas along the length of the sensor, which can show glide and provide feedback to prevent slippage. Synthetic Muscle™ was also retrofitted as actuator systems into off-the-shelf robotic grippers and considered in novel biomimetic gripper designs. Human grasp is gentle yet firm, with tactile touch feedback. The combination of our EAP shape-morphing and sensing features promises the potential for robotic grippers with human hand-like control and tactile sensing. This work is expected to advance robotics, whether it is for agriculture, medical surgery, therapeutic or personal care, or in extreme environments where humans cannot enter, including with contagions that have no cure, as well as for collaborative robotics to allow humans and robots to intuitively work safely and effectively together.
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