*Article* **An Electret/Hydrogel-Based Tactile Sensor Boosted by Micro-Patterned and Electrostatic Promoting Methods with Flexibility and Wide-Temperature Tolerance**

**Zhensheng Chen <sup>1</sup> , Jiahao Yu <sup>1</sup> , Haozhe Zeng <sup>1</sup> , Zhao Chen <sup>1</sup> , Kai Tao 1,\* , Jin Wu 2,\* and Yunjia Li 3,\***


**Abstract:** With the rising demand for wearable, multifunctional, and flexible electronics, plenty of efforts aiming at wearable devices have been devoted to designing sensors with greater efficiency, wide environment tolerance, and good sustainability. Herein, a thin film of double-network ionic hydrogel with a solution replacement treatment method is fabricated, which not only possesses excellent stretchability (>1100%) and good transparency (>80%), but also maintains a wide application temperature range (−10~40 ◦C). Moreover, the hydrogel membrane further acts as both the flexible electrode and a triboelectric layer, with a larger friction area achieved through a micro-structure pattern method. Combining this with a corona-charged fluorinated ethylene propylene (FEP) film, an electret/hydrogel-based tactile sensor (EHTS) is designed and fabricated. The output performance of the EHTS is effectively boosted by 156.3% through the hybrid of triboelectric and electrostatic effects, which achieves the open-circuit peak voltage of 12.5 V, short-circuit current of 0.5 µA, and considerable power of 4.3 µW respectively, with a mentionable size of 10 mm × 10 mm × 0.9 mm. The EHTS also demonstrates a stable output characteristic within a wide range of temperature tolerance from −10 to approximately 40 ◦C and can be further integrated into a mask for human breath monitoring, which could provide for a reliable healthcare service during the COVID-19 pandemic. In general, the EHTS shows excellent potential in the fields of healthcare devices and wearable electronics.

**Keywords:** flexible electronics; electret/hydrogel-based tactile sensors; pyramidal parented hydrogel; anti-freezing and anti-drying
