Fabricated using flexible, stretchable, and electrically conductive nanomaterials called MXenes, novel strain sensors were developed that are ultra-thin, battery-free, and can transmit data wirelessly. By controlling the surface textures of MXenes, researchers were able to control the sensing performance of strain sensors for various soft exoskeletons. The sensor design principles developed will significantly enhance the performance of electronic skins and soft robots.
The sensors can be coated on a robotic arm like an electronic skin to measure subtle movements as they are stretched. When placed along the joints of robotic arms, the sensors allow the system to understand precisely how much the robotic arms are moving and their current position relative to the resting state. Current off-the-shelf strain sensors do not have the required accuracy and sensitivity to carry out this function.
One area where the strain sensors could be put to good use is in precision manufacturing, where robotic arms are used to carry out intricate tasks such as fabricating fragile products like microchips. Conventional automated robotic arms used in precision manufacturing require external cameras aimed at them from different angles to help track their positioning and movement. The ultra-sensitive strain sensors will help improve the overall safety of robotic arms by providing automated feedback on precise movements with an error margin below one degree and remove the need for external cameras, as they can track positioning and movement without any visual input.
The technological breakthrough is the development of a production process that allows researchers to create highly customizable ultra-sensitive sensors over a wide working window with high signal-to-noise ratios. A sensor’s working window determines how much it can stretch while still maintaining its sensing qualities and having a high signal-to-noise ratio means greater accuracy, as the sensor can differentiate between subtle vibrations and minute movements of the robotic arm.
This production process allows the team to customize their sensors to any working window between 0 and 900 percent while maintaining high sensitivity and signal-to-noise ratio. Standard sensors can typically achieve a range of up to 100 percent. By combining multiple sensors with different working windows, researchers can create a single ultra-sensitive sensor that would otherwise be impossible to achieve.
The advanced flexible sensors give soft wearable robots an important capability in sensing a patient’s motor performance, particularly in terms of their range of motion. This will ultimately enable the soft robot to better understand a patient’s ability and provide the necessary assistance to their hand movements.
The team is also looking to improve the sensor’s capabilities in soft exoskeleton robots for rehabilitation and in surgical robots for transoral robotic surgery. Cancerous tissues, for instance, feel different from normal, healthy tissues. By adding ultra-thin wireless sensing modules to long robotic tools, surgeons can reach and operate in areas where their hands can’t reach and potentially “feel” the tissue stiffness without the need for open surgery.