Functional Hybrid Materials on Bio-Basis for Sensors and Actuators

Cellulose nanofibrils (CNFs) are an abundant, bio-based, and renewable material with excellent mechanical properties. They show highest strength and allow for light-weight applications. In order to functionalize this sustainable material par excellence, the fabrication of hybrid materials is mandatory. These hybrid materials include functional polymers as well as advanced core-shell and metallic nanoparticles. Here, the knowledge of the nanostructure is crucial for its application. Starting from thin film technology, spray deposition is a scalable, facile, and industrially used method for fabricating tailored nanostructures with specific applications. To start with, sprayed CNF templates themselves act as nanoporous templates for optoelectronic applications. They comprise non-swelling polymer electrodes¹, sensor materials², flexible electrodes³, and tunable amorphous photonic crystals⁴. Being all water-based, the interaction with water is crucial⁵. Using water-based polymers and CNF in a hybrid material and facile solution casting, internal stresses and humidity sensitivity is exploited to fabricate self-healing actuators⁶.<br/>In my talk I will present the fundamental aspects of using CNF and characterizing its response to water and humidity. The nanoporous structure of CNF thin films is the key-point for their functionalization. The nanostructure is extracted using advanced X-ray and neutron scattering methods, which allows to understand and exploit the interaction with water of the hybrid materials applied in soft robotics.<br/><br/>1. Brett, C. J. et al. Humidity-Induced Nanoscale Restructuring in PEDOT:PSS and Cellulose Nanofibrils Reinforced Biobased Organic Electronics. Adv. Electron. Mater. <b>7</b>, 2100137 (2021).<br/>2. Chen, Q. et al. Biopolymer-Templated Deposition of Ordered and Polymorph Titanium Dioxide Thin Films for Improved Surface-Enhanced Raman Scattering Sensitivity. Adv. Funct. Mater. <b>32</b>, 2108556 (2022).<br/>3. Betker, M. et al. Sprayed Hybrid Cellulose Nanofibril-Silver Nanowire Transparent Electrodes for Organic Electronic Applications. ACS Appl. Nano Mater. <b>6</b>, 13677-13688 (2023).<br/>4. Harder, C. et al. Optical Properties of Slot-Die Coated Hybrid Colloid/Cellulose-Nanofibril Thin Films. Adv. Opt. Mater. <b>11</b>, 202203058 (2023).<br/>5. Brett, C. J. et al. Water-Induced Structural Rearrangements on the Nanoscale in Ultrathin Nanocellulose Films. Macromolecules <b>52</b>, 4721-4728 (2019).<br/>6. Chen, Q. et al. Cellulose-Reinforced Programmable and Stretch-Healable Actuators for Smart Packaging. Adv. Funct. Mater. <b>32</b>, 2208074 (2022).