Ultrathin Small-Sized Graphene Oxide-Modified MXene Hybrid Films for Highly Sensitive Transparent Strain Sensors

Highly sensitive and transparent strain sensors based on the tunneling effect of two-dimensional (2D) materials have attracted considerable interest in imperceptible soft electronics, such as health monitoring, e-skins, and smart displays. However, achieving both high sensitivity and transparency remains a challenge and obstacle for strain sensors. In this work, highly sensitive and transparent strain sensors are realized through incorporating small-sized graphene oxide (SGO) nanosheets into ultrathin stacked MXene flakes to produce SGO-modified MXene (SGO-mM) hybrid films via Langmuir-Schaefer assembly. It is found that SGO with a submicrometer lateral size is crucial for improving the alignment and compactness of MXene flakes within the ultrathin stacked structure. The SGO-mM hybrid film, with a transmittance of 86%, demonstrates a high gauge factor of 115.6 and a detection limit as low as 0.1% strain due to the enhanced tunneling effect and improved tribological properties at the friction interface, as revealed by molecular dynamics simulations. Strain-sensing platforms for pulse monitoring, speech recognition, and sign language translation, as well as sensor arrays for spatially resolved stress distribution mapping, are further prototyped using the developed SGO-mM hybrid films, showcasing their great potential in wearable electronics. The simultaneously enhanced sensitivity and transparency provide critical insights into the design of high-performance MXene- or other 2D-material-based transparent strain sensors.