Biodegradable, Self-healing, Recyclable, Conductive Coatings for Wearable Electronics and Soft Robotics

Electrically conductive coatings are essential for transitioning electronic components and circuitry from stiff and rigid substrates to more flexible and stretchable platforms, such as thin plastics, textiles, and foams.[1] In parallel, the push for more sustainable, biodegradable, and cost-efficient conductive inks to coat these substrates has led to the development of innovative formulations involving biopolymers and nanomaterials that results in soft composites layer with unique functionalities.<br/>The proposed talk unveils diverse electrically conductive coating (resistivity ≈10^-4 Ω m) that entails salient properties such as broad substrate types paintability, tunable piezoresistivity, self-healing, tunable degradability, and recyclability. Such a broad collection of properties is obtained simply by changing the substrates employed, the binders, and the conductive nanofillers.<br/>Particularly, one new class of coating based on biobased and biodegradable vitrimer binders is proposed. Using the vitrimer ensures satisfying adhesion to diverse substrates, flexibility, and recyclability of the conductive coating. This coating enables human-mimicking soft robotics skin since it is self-healing and biodegradable. Tests for the live monitoring of SoftHand3, the grasping system of many worldwide diffused robots, have yielded promising results. The use of biodegradable ingredients and the possibility of recycling makes it an appealing material to face the sustainability issue of today's electronics and robotics.<br/>Another class of coating proposed is applied to textiles. Such coatings have controllable electrical resistance change with deformation and transiency (i.e., dissolution in water).[2] The modulation of the piezoresistivity and transiency is obtained by controlling the nanofiller geometry, binder composition, and textile twill orientation. The electrical resistance shows an anisotropic response to bending depending on the composition of the coating and the stress direction, functioning either as a deformable compliant electrode or a tunable piezoresistor. Indeed, it can withstand thousands of bending cycles with a change in resistance of less than 5% or change its resistance by many orders of magnitude with the same deformation thanks to the combination of cotton twill and different nanofillers. A simple modification in the binder composition adding waterborne polyurethane, allows the coating to go from entirely transient in water within minutes to withstanding simulated washing cycles for hours without losing its electrical conductivity. This versatile green conductor may serve opposing needs by altering the material composition and the deformation direction.<br/><br/>References:<br/>[1] Vicente Orts Mercadillo, Kai Chio Chan, Mario Caironi, Athanassia Athanassiou, Ian A. Kinloch, Mark Bissett, Pietro Cataldi, <i>Electrically Conductive 2D Material Coatings for Flexible and Stretchable Electronics: A Comparative Review of Graphenes and MXenes, </i><u>Advanced Functional Materials</u>, <b>2022</b>.<br/>[2] Pietro Cataldi, Pietro Steiner, Mufeng Liu, Gergo Pinter, Athanassia Athanassiou, Coskun Kocabas, Ian A Kinloch, Mark A Bissett, <i>A Green Electrically Conductive Textile with Tunable Piezoresistivity and Transiency</i>, <u>Advanced Functional Materials</u>, <b>2023</b>.