Surface charge manipulation for improved humidity sensing of TEMPO-oxidized cellulose nanofibrils

Jiaying Zhu; Penghui Zhu; Yeling Zhu; Yuhang Ye; Xia Sun; Yifan Zhang; Orlando J Rojas; Peyman Servati; Feng Jiang

doi:10.1016/j.carbpol.2024.122059

Surface charge manipulation for improved humidity sensing of TEMPO-oxidized cellulose nanofibrils

Carbohydr Polym. 2024 Jul 1:335:122059. doi: 10.1016/j.carbpol.2024.122059. Epub 2024 Mar 15.

Authors

Jiaying Zhu¹, Penghui Zhu², Yeling Zhu³, Yuhang Ye³, Xia Sun³, Yifan Zhang³, Orlando J Rojas⁴, Peyman Servati⁵, Feng Jiang⁶

Affiliations

¹ Sustainable Functional Biomaterials Laboratory, Bioproducts Institute, Department of Wood Science, The University of British Columbia, Vancouver V6T 1Z4, Canada; Flexible Electronics and Energy Lab, Department of Electrical and Computer Engineering, The University of British Columbia, Vancouver V6T 1Z4, Canada.
² Sustainable Functional Biomaterials Laboratory, Bioproducts Institute, Department of Wood Science, The University of British Columbia, Vancouver V6T 1Z4, Canada. Electronic address: penghui1@mail.ubc.ca.
³ Sustainable Functional Biomaterials Laboratory, Bioproducts Institute, Department of Wood Science, The University of British Columbia, Vancouver V6T 1Z4, Canada.
⁴ Bioproducts Institute, Department of Chemical & Biological Engineering, Department of Chemistry and Departments of Wood Science, The University of British Columbia, Vancouver V6T 1Z4, Canada.
⁵ Flexible Electronics and Energy Lab, Department of Electrical and Computer Engineering, The University of British Columbia, Vancouver V6T 1Z4, Canada. Electronic address: peymans@ece.ubc.ca.
⁶ Sustainable Functional Biomaterials Laboratory, Bioproducts Institute, Department of Wood Science, The University of British Columbia, Vancouver V6T 1Z4, Canada. Electronic address: feng.jiang@ubc.ca.

PMID: 38616073
DOI: 10.1016/j.carbpol.2024.122059

Abstract

Cellulose-based humidity sensors have attracted great research interest due to their hydrophilicity, biodegradability, and low cost. However, they still suffer from relatively low humidity sensitivity. Due to the presence of negatively charged carboxylate groups, 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-oxidized cellulose nanofibril (CNF) exhibits enhanced hydrophilicity and ion conductivity, which is considered a promising candidate for humidity sensing. In this work, we developed a facile strategy to improve the humidity sensitivity of CNF films by regulating their surface charge density. With the increase in surface charge density, both water uptake and charge carrier densities of the CNF films can be improved, enabling a humidity sensitivity of up to 44.5 % (%RH)^-1, higher than that of most polymer-based humidity sensors reported in the literature. Meanwhile, the sensor also showed good linearity (R² = 0.998) over the 15-75 % RH at 1 kHz. With these features, the CNF film was further demonstrated for applications in noncontact sensing, such as human respiration, moisture on fingertips, and water leakage, indicating the great potential of CNF film in humidity monitoring.

Keywords: Capacitance; Cellulose nanofibrils; Humidity sensor; Ionic conductivity; Surface charge density.