Kappa(κ)Chip: a modular microfluidic device for analyte screening using parallelized assays and a multiple shear rate approach.

Polymers are ubiquitous in the modern world, but many have low surface energies, making it difficult to engineer adhesive interactions with them. The large sequence space afforded by biology, along with its ability to evolve novel solutions to challenging problems, makes exploring bioinspired materials for novel adhesives attractive. However, the discovery of biologically-inspired adhesive modalities demands the development of high-throughput screening methods that use only small amounts of material, making microfluidics an ideal solution. In this work, we present the development of a novel microfluidic chip, the kappa(κ)Chip, which represents a significant leap in testing efficiency. The parallelized design of the kappa(κ)Chip enables 24 simultaneous adhesion tests from a single-input stream. This drastically reduces experimental time and reagent consumption, allowing for more comprehensive datasets and the ability to quickly compare the performance of multiple proteins against different substrates-a capability unavailable with current single-test platforms. The chip was used to evaluate the adhesive properties of fungal hydrophobin proteins engineered for display on the surface of cells, using the adhesion of the cells as a proxy for the ability of hydrophobins to serve as an adhesive. The device combines microfabrication, microfluidics, material sciences, synthetic biology, multiphysics simulation and ML in a unique way to enable the discovery of strong biological adhesives. The rapid screening capability of the kappa(κ)Chip facilitates an informed rank-ordering of potential binding motifs or sequences against arbitrary substrates. Moreover, this platform holds potential for applications in investigating cell adhesion in tissue and organ environments, as well as in studies of marine fouling.