Stretchable hydrogel-based strain sensors suffer from limited sensitivity, which urgently requires further breakthroughs for precise and stable human-computer interaction. Here, an efficient microstructural engineering strategy is proposed to significantly enhance the sensitivity of hydrogel-based strain sensors by sandwiching an emulsion-polymerized polyacrylamide organohydrogel microsphere membrane between two Ecoflex films, which are accompanied by crack generation and propagation effects upon stretching. Consequently, the as-developed strain sensor exhibits ultrahigh sensitivity (gauge factor (GF) of 1275), wide detection range (100% strain), low hysteresis, ultralow detection limit (0.05% strain), good fatigue resistance, and low fabrication cost. In addition, the sensor features good water, dehydration, and frost resistance, enabling real-time strain monitoring in various complex conditions due to the encapsulation of Ecoflex film and the addition of glycerol and KCl. Through further structural manipulation, the device achieves superior response to tiny strains, with a GF value of 98.3 in the strain range of less than 1.5%. Owing to the high strain sensing performance, the sensor is able to detect various human activities from swallowing to finger bending even under water. On this basis, a wireless sensing system with apnea warning and single-channel gesture recognition capabilities is successfully demonstrated, demonstrating its great promise as wearable electronics.
We present green organohydrogel-based stretchable (up to 700% strain), transparent, and room-temperature O 2 sensors with impressive performance, including drying and freezing tolerances, high sensitivity, broad detection range (100 ppm-100%), long-term stability, low theoretical detection limit (0.585 ppm), linearity, and the capability to real-time monitor human respiration by directly attaching on human skin. A facile solvent replacement approach is employed to partially exchange water with natural and edible xylitol/sorbitol molecules, generating stable, green and tough organohydrogels. Compared with the pristine hydrogel counterpart, the organohydrogel-based O 2 sensors feature higher stability, prolonged life time (140 days) and the ability to work over a wide range of temperatures (À38 to 65 C). The O 2 sensing mechanism is elucidated by investigating the redox reactions occurred at the electrode-hydrogel interface. This work develops a facile strategy to fabricate stretchable, transparent, and high-performance O 2 sensor using stable and green organohydrogels as novel transducing materials for practical wearable applications.
K E Y W O R D Santi-freezing and anti-drying hydrogel, conductive and green organohydrogel, redox reaction sensing mechanism, stretchable and room-temperature oxygen sensor, xylitol and sorbitol Yuanqing Lin and Zixuan Wu contributed equally to this work.
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