An Integrated and Flexible Humidity Sensor for Noncontact Handwriting Recognition

The demand for human–machine interfaces (HMIs) is soaring with the rapid development of wearable electronics. However, current HMIs typically operate in contact sensing mode, which can cause interface contamination, and require the combination of rigid sampling circuits. Therefore, revolutionary integrated noncontact flexible HMI systems are eagerly anticipated. In this work, a 4 × 4 flexible humidity sensing array and a designed flexible sampling circuit are directly integrated to form a noncontact handwriting recognition system. The humidity sensing array is fabricated by screen printing the interdigital electrode array on PET substrate with MXene acting as the humidity‐sensitive film. The sensor works in noncontact mode in response to human respiration and fingertip humidity fields. The flexible sampling circuit allows simultaneous acquisition of 16 port signals and transmission to the computer. Combined with a convolutional neural network, the average accuracy of the noncontact handwriting recognition system for recognizing handwriting digits 1–9 is achieved to be highly 98.67%. The noncontact handwriting recognition system is further applied to control a mechanical hand to visualize handwriting digits in real time. This noncontact handwriting recognition system expands a new path for humidity sensors and shows an exceptional application prospect in the next generation of HMI and touchless medical equipment.