Superhydrophobic Polydimethylsiloxane/CNT/Spandex Composites as Flexible Multifunctional Strain Sensors

Recently, the field of intelligent wearable electronics regarding conductive elastomer composites has garnered considerable research interest. However, achieving a wide strain response range, high sensitivity, and superhydrophobicity simultaneously remains a challenge. Herein, 250-denier Spandex fibers were used as a flexible matrix, whereas low-cost carbon nanotubes (CNTs) served as a conductive filler. The CNTs were uniformly, rapidly, and spontaneously anchored the surface of the Spandex fibers through a method combining ultrasound and swelling. Subsequently, polydimethylsiloxane (PDMS) was employed for modification, resulting in a PDMS/CNT/Spandex composite material with a uniformly hierarchical micro–nanostructure. The composite material exhibited high sensitivity (with a maximum gauge factor of 417.92 within a strain range of 495%–525%), fast response/recovery times (100 ms/300 ms), and exceptional reliability over an ultra–wide strain range spanning from 0.1% to 525% and maintains good repeatability and stable response even after undergoing 2000 stretch–release cycles. Moreover, it possesses outstanding water-repellent and corrosion–resistant properties, enabling effective performance under harsh environmental conditions. This material is compact and portable, allowing for its seamless integration into textiles without compromising comfort. It can help detect several human activities, including subtle actions (e.g., vocal cord vibrations) and large-scale movements (e.g., joint bending), wirelessly transmit real-time signals of finger movements to mobile phones through Bluetooth technology, and enable real-time monitoring of airflow rate (ranging from 8 to 36 m3/h) by facilitating the construction of a simple gas flow testing system. Furthermore, weaving composite materials into tactile electronic networks could influence the mapping of 2D resistance changes to determine the weight and shape of objects. Therefore, this study provides a simple and versatile method to prepare high-performance strain sensors with considerable application potential in human movement monitoring, electronic skin, and human–computer interaction.