Highly Sensitive, Stretchable Strain Sensor Based on Ag@COOH‐Functionalized CNTs for Stroke and Pronunciation Recognition

Abstract Combining metal and carbon nanomaterials is an effective way to significantly enhance the performance of soft strain sensors. The role of carbon nanotubes (CNTs) functionalized with different chemical groups in improving the properties of nanosilver‐coated carbon nanotubes (Ag@CNT) is investigated. The functionalized CNTs are first calculated with different chemical groups combined with the silver atoms. Ag@COOH‐functionalized CNTs exhibit greater binding energy and a smaller bandgap, which leads to better hydrophilicity, stability, and stronger bonding. Ag@CNTs are then synthesized using pristine CNT, OH‐functionalized CNT, and COOH‐functionalized CNT. Strain sensors are fabricated by wrapping the sensing material with polydimethylsiloxane (PDMS) to form a sandwich structure. Tests of these sensors are consistent with the simulation results; that is, COOH‐functionalized CNTs can greatly enhance the performance of Ag@CNT. In particular, Ag@COOH‐functionalized CNT sensors exhibit a strain range of nearly 40%, an initial resistance of 6.83 Ω, and excellent sensitivity, with a GF of 172. They can be applied in stroke detection and pronunciation recognition. This system also has great potential for foldable phones and flexible writing pads.