Near-Field Electrospinning Enabled Highly Sensitive and Anisotropic Strain Sensors

The rapid advances in manufacturing technologies have provided great opportunities for scalable fabrication of novel sensing structures and devices. Here, the application of near-field electrospinning to the fabrication of flexible strain sensors is explored. Through theoretical modeling, it is first verified that a strong anisotropic response of a strain sensor can be obtained through introducing a grid-shaped design to its sensing layer. Following this guideline, near-field electrospinning is applied to fabricate polyurethane grids with well-controlled period and thickness and the grid is further decorated with conductive silver nanowires. Through tuning the structure of the polyurethane grid and the density of the silver nanowires, a high gauge factor (GF = 338.47) under high strain (200%) is achieved, representing the best sensing and stretching property combination reported for flexible strain sensors. In good agreement with the theoretical model, the strain sensors are only sensitive to the strain along the electrode direction and are insensitive to perpendicular direction strains. Based on this characteristic response, the excellent capability of the strain sensors in distinguishing hand movement and monitoring physiological signals is demonstrated, suggesting the great application potential of the sensors in robotic vision and prosthesis.