Sono Assembly and Healing of Nanomaterials Network on Polymer Substrate

Nanomaterial-based flexible electronics (NFEs) that integrate the functionality of nanomaterials and the flexibility of polymer substrates promise to revolutionize a wide range of industries, from electronics and energy to healthcare. The potential health and environmental concern of releasing nanomaterials and polymers into the environment and the use of toxic solvents and agents in the manufacturing process presents a significant challenge for next-generation manufacturing technologies. Eco-manufacturing represents an important trend for the advanced manufacturing of NFEs, in which researchers not only consider the technical challenges of integrating two drastically different components in a high throughput manner, they also address the issues related to the energy consumption, health and environmental impacts over the entire device lifecycle. Here, we have combined an interfacial energy design of a nanomaterial-polymer-solvent system with a sono-matter interaction mechanism, to achieve ultrafast assembly and healing of a nanomaterial network on a polymer substrate using deionized (DI) water as the solvent. This research resulted in the invention of an ultrafast but self-limiting sono dip coating (SDC) method and the creation of a new sono-healing protocol. Unlike the traditional dip-coating assembly process, in this SDC method, a dry polymer substrate with assembled nanomaterials is directly withdrawn from the solution, and the evaporation process is eliminated. The withdrawal speed can reach 16 m/min_, which is 1 to 5 orders of magnitude higher than any other nanomaterials dip-coating system and at least an order of magnitude higher than the maximum speed of commercial desktop dip-coaters. Because of the elimination of the evaporation process, cyclic dip coating can be performed continuously to control the thickness and coverage of the assembled film. We have found that the assembly is a self-limiting process; the assembled film thickness and resistance quickly reach a plateau. Importantly, using graphene-PDMS devices, we demonstrated that the nanomaterial network that was damaged after mechanical deformations can recover its conductivity and regenerate its functionality through a simple, a minute-long, sono-healing treatment. Further, the assembly method can be integrated with other manufacturing processes, making it suitable for fabricating integrated circuits and realizing a wide range of functionalities. As a proof of concept, we showed the integration of SDC with electroplating and deposited nickel and Ti₃C₂T_x MXene films onto graphene. Those hybrids showed excellent electromagnetic interference shielding ability and very good electrochemical performance. This work not only establishes a novel strategy for assembly and repair of nanomaterial films but also paves the way towards rational design and eco-manufacturing of large scale, integrated, reusable, and affordable flexible electronics.