Protein jetting-based printing: principles and applications

Protein jetting-based printing emerged as a powerful technology at the intersection of biotechnology, materials science, and microfabrication. Building on the intrinsic biocompatibility, biodegradability, and versatility of proteins, it facilitates the development of novel functional materials, by enabling precise, contactless deposition of protein-based inks onto a wide range of substrates while preserving their bioactivity. Since its initial applications in the late 1980s, protein jetting-based printing has advanced considerably, driven by innovations in both protein-based ink formulation and printing technologies. This review provides a comprehensive overview of the evolution and current state of protein jetting-based printing, with particular focus on the critical role of ink formulation in meeting the specific requirements of various printing systems, including thermal, piezoelectric, electrohydrodynamic (EHD), and microvalve-based. Key challenges in protein-based ink design for jetting-based printing are discussed in detail, including physicochemical and rheological constraints, preservation of protein activity, and the iterative nature of ink formulation optimization to meet both protein- and system-specific demands. Applications in biosensors, bio-microelectromechanical systems (Bio-MEMS), tissue engineering, and drug delivery are highlighted, along with current limitations. Addressing these challenges will be essential for the broader adoption of protein jetting-based printing for the sustainable microfabrication of next-generation protein-engineered materials.