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Conjugated polymers exhibit electrically driven volume changes when included in electrochemical devices via the exchange of ions and solvent. So far, this volumetric change is limited to 40% and 100% for reversible and irreversible systems, respectively, thus restricting potential applications of this technology. A conjugated polymer that reversibly expands by about 300% upon addressing, relative to its previous contracted state, while the first irreversible actuation can achieve values ranging from 1000–10 000%, depending on the voltage applied is reported. From experimental and theoretical studies, it is found that this large and reversible volumetric switching is due to reorganization of the polymer during swelling as it transforms between a solid‐state phase and a gel, while maintaining percolation for conductivity. The polymer is utilized as an electroactive cladding to reduce the void sizes of a porous carbon filter electrode by 85%. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new paradigm for implementation of in vivo biofuel cell electrodes is investigated. • In vivo mapping of the molecular content of a leaf is performed using electrochemistry. • Polymerization of electroactive materials in the vascular system of a plant is presented. We investigate the possibility of producing biofuel cell electrode materials in vivo by injecting the reagents directly into plant tissues. We first introduce model electroactive substances Fe(CN) 6 4− and Ru(NH 3) 6 3+ into a Nicotiana tabacum leaf. In situ electrochemical measurements make it possible to trace the distribution of these substances. As well as mapping the vascular content, electrochemistry can be used to trigger reactions directly inside the plant. The injection of thiophene (T) and ethylenedioxythiophene (E)-based trimers (ETE) anchoring an Os(2,2′-bipyridine) 2 (1-(3-aminopropyl)-imidazole)Cl Os-complex followed by the application of anodic polarization triggers a polymerization reaction in the region of the plant vascular system containing the monomer, showing that it is possible to generate electroactive organic macromolecules locally in vivo. [ABSTRACT FROM AUTHOR]