In recent years, flexible sensors have revolutionized the field of sensing capabilities with their ability to detect a wide range of stimuli. However, the measurement of complex deformations resulting from forces or strains from multiple axes presents a significant challenge due to the lack of independent perception of multi-axial stimuli. The main obstacle in achieving this independent perception lies in the Poisson’s effect of sensing materials, which hinders the accurate measurement of biaxial stimuli. To address this issue, researchers have turned to zero Poisson’s ratio (ZPR) materials, which maintain a constant transverse width under longitudinal strain, offering a solution to the interference problems in multi-axial stimuli perception.
One of the leading researchers in this field, Prof. Hao Wu, along with Dr. Xin Huang, embarked on a study to explore the potential of achieving zero Poisson’s ratio structures. The team proposed a novel approach of combining traditional positive Poisson’s ratio (PPR) structures with negative Poisson’s ratio (NPR) structures to create a hybrid structure that could effectively achieve zero Poisson’s ratio. By varying the feature size and width of the hybrid structure, the researchers were able to manipulate the Poisson’s ratio between positive and negative values. Through finite element analysis, they identified the optimal parameters required to fabricate ZPR membranes successfully.
The ZPR membranes developed by the research team exhibited a significantly reduced Poisson’s ratio compared to conventional membranes, showcasing the effectiveness of the hybrid structure in decreasing Poisson’s ratio. These ZPR flexible sensors demonstrated the capability to accurately detect both uniaxial and biaxial stimuli, offering a new level of independence in sensing capabilities. When subjected to uniaxial stretching, the ZPR sensors displayed a linear increase in electric resistance along the stretching direction, while exhibiting minimal changes in resistance perpendicular to the stretching direction. This unique feature enabled the sensors to independently detect strains along specific axes, opening up a myriad of possibilities for complex deformation detection.
The applications of ZPR flexible sensors extend far beyond traditional sensing technologies, with the ability to accurately measure force, strain, and motion in scenarios involving robotic manipulation and locomotion. These sensors can detect contact forces between rigid manipulators and grasped objects, regardless of the deformations of the objects, offering invaluable feedback for robotic interactions. By combining perpendicular sensing units on manipulators, ZPR sensors can indicate the bending of fingers and detect collisions with obstacles, enhancing both safety and dexterity in robotic applications. Moreover, ZPR flexible sensors play a crucial role in detecting the locomotion distance and direction of biaxial soft robots, further expanding their utility in the field of robotics.
Prof. Wu emphasized the tremendous potential of ZPR sensors in various fields, including healthcare, human-machine interfaces, and robotic tactile sensing. The exotic sensing capabilities of ZPR sensors offer unprecedented opportunities for innovation and advancement in sensor technologies, paving the way for a future where complex deformations can be accurately detected and analyzed with precision. As researchers continue to explore the possibilities of ZPR materials and structures, the realm of flexible sensors holds immense promise for transforming the way we perceive and interact with the world around us.
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