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Published July 10, 2023 | Published
Journal Article Embargoed

Ion transport in thermally responsive pectin film

  • 1. ROR icon California Institute of Technology


The ionic conductivity of CaCl₂-crosslinked pectin was found to exhibit a record-high temperature response, suggesting its potential applications in wearable devices and infrared sensors [R. Di Giacomo et al., Sci. Rob. 2, eaai9251 (2017)]. However, little was known about its ion conduction mechanisms and the origin of its high-temperature sensitivity. In this study, we perform controlled experiments and identify calcium ions as the dominant current carriers. By analyzing infrared spectra at different temperatures, we find that the temperature response is due to changes in ion mobility, rather than variations in ion number density. We compare measurements and modeling results of nine different multivalent ions and find a positive correlation between their temperature responses and their binding energy to pectin. While these findings are fundamental in nature, they provide relevant guidance for the future design of temperature-sensitive polymers and other materials for organic electronics.

Copyright and License

© 2023 Author(s). Published under an exclusive license by AIP Publishing.


This research was funded in part by the Samsung Electronic GRO Program and in part by the HMRI program at Caltech. We are grateful to the Molecular Materials Research Center (MMRC) in the Beckman Institute of the California Institute of Technology (Caltech) for access to their experimental facilities. We thank Dr. Bruce S. Brunschwig from MMRC and Dr. Yeong Suk Choi from Samsung for useful discussions. The computations presented here were conducted in the Resnick High Performance Computing Center, a facility supported by the Resnick Sustainability Institute at the California Institute of Technology.


Linghui Wang: Conceptualization (lead); Data curation (lead); Formal analysis (lead); Investigation (lead); Methodology (lead); Software (lead); Validation (lead); Visualization (lead); Writing – original draft (lead); Writing – review & editing (lead). Tae Hyun Kim: Data curation (supporting); Methodology (supporting); Resources (supporting); Writing – review & editing (supporting). Vincenzo Costanza: Conceptualization (supporting); Resources (supporting); Validation (supporting); Writing – review & editing (supporting). Nicholas J. Higdon: Formal analysis (supporting); Validation (supporting); Writing – review & editing (supporting). Chiara Daraio: Conceptualization (equal); Formal analysis (equal); Funding acquisition (equal); Investigation (equal); Methodology (equal); Project administration (equal); Resources (equal); Supervision (equal); Validation (equal); Writing – review & editing (equal).

Data Availability

Most of the data support the findings of this study are available within the paper. The data that support the findings of this study are available from the corresponding author upon reasonable request.

See the supplementary material for additional details on the sample fabrication, electrical measurements, infrared spectroscopy, and DFT calculation.

Conflict of Interest

The authors have no conflicts to disclose.



The files will be made publicly available on July 10, 2024.

Additional details

October 27, 2023
October 27, 2023