Green innovations in natural paper ink: trends, applications, and future prospects

Natural inks have emerged as eco-friendly alternatives to synthetic inks in the paper printing industry due to their biodegradability, non-toxicity, and sustainability. Derived from renewable sources such as plants, algae, minerals, and fungi, these inks reduce environmental pollution and dependence on petroleum-based materials. This review highlights recent advancements in natural ink extraction, formulation, and application, emphasizing improvements in physical and chemical properties. Studies show natural indicator inks using Lycium ruthenicum anthocyanins achieve a sensitivity of 2178.57 μA mM⁻¹ cm⁻² with a rapid response time of 18 s. Cobalt blue pigments derived from dolomite and kaolin tailings demonstrate high color performance (L* = 37.63, a* = 10.68, b* = −54.87) and 94.96 % light absorption efficiency. Packaging papers containing triticale straw fibers reduced color variation (ΔE*) by 20 % after aging and rubbing tests. Plasma treatment and nano-chitosan coatings have improved color depth by up to 214 % and washing durability after 45 cycles. Despite these advancements, challenges remain in enhancing color fastness, water resistance, and scalability. This review outlines future research directions focused on advanced extraction, formulation optimization, and life cycle assessments to promote the industrial application of sustainable natural inks.