We used a poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)/carbon nanotube (CNT) composite as a temperature sensing layer, and the device exhibited a high sensitivity of -2.46%/°C. A sandpaper-molded PDMS with fluorinated surface modification protection layer was used as the superhydrophobic, oleophobic, self-cleaning protective encapsulation layer. This device exhibits a self-cleaning function when it makes contact with liquids such as water, tea, coffee, and milk. In addition, the surface can also repel liquids with low surface tension (such as oil), exhibiting good oleophobicity. Resistance to ultrasonication in an organic solvent for 120 min and a 400-cycle tape peel test reveal durability of this device. The device functions under similar conditions after 1000 bending cycles with a bending radius of 0.875 mm. In this work, we demonstrate a simple and low-cost technique to fabricate durable and wearable temperature sensing devices.
This study fabricated temperature sensors with a mixture of carbon nanotube (CNT) and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS). CNT/PEDOT:PSS solutions with three different ratios—1/5, 1/9, and 1/13—were prepared and aged for 0, 3, and 6 days. The temperature sensor was fabricated by drop-casting the aged solution onto a flexible polydimethylsiloxane (PDMS) substrate. As the aging time of CNT/PEDOT:PSS solutions with ratios of 1/5, 1/9, and 1/13 increased to 6 days, the temperature coefficient of resistance (TCR) of CNT/PEDOT:PSS decreased from -1.97, -1.99, and -2.15 (%/°C) to -2.80, -2.61, and -2.51 (%/°C) (i.e. temperature sensitivity increased) and temperature index (TI) also increased from 2242.5, 2249.1, and 2503.8 (K) to 3530.1, 3085.7, and 3002.5 (K), respectively. As the aging time of CNT/PEDOT:PSS solution increased to 6 days, its Seebeck coefficient increased from 52.4 to 114.5 μV K−1. These results show that the aging of CNT/PEDOT:PSS solution significantly increased the temperature sensitivity and Seebeck coefficient via the de-doping of PEDOT:PSS. This serves as a facile method to improve the temperature sensitivity of the CNT/PEDOT:PSS composite.
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