Optimization of drop-on-demand 3D printing of natural latex ink for the fabrication of customized medical splints

Abstract

A novel drop-on-demand (DoD) 3D printing system was developed to fabricate complex-shaped products using natural latex ink. The printing parameters were systematically optimized based on the roundness and deposition behavior of rubber droplets, with 75 % alcohol identified as the most effective medium among various acid coagulants. The latex, formulated with a viscosity of 800 cP, was tailored to ensure printability and structural integrity. Optimal conditions—including a 0.85 mm nozzle diameter, a deposition rate of 45 mm³/s, an alcohol bath height of 3 mm, and a nozzle tip height of 10 mm from the medium surface—enabled the successful fabrication of a custom-designed palm splint featuring intricate geometry within 70 min. Dimensional comparison between the digital model and the printed splint in the X-Z and Y-Z planes revealed a deviation of only 9.89 %, which is acceptable for personalized medical devices. The printed splint exhibited a porous structure that enhances breathability and conformed precisely to the user's hand. Mechanical testing showed that the deposited rubber achieved a tensile strength exceeding 4.5 MPa and an elongation at break greater than 950 %, with droplet roundness values approaching unity. This DoD 3D printing approach significantly reduces material preparation time and production costs, offering a promising pathway for the rapid, cost-effective manufacturing of customized rubber-based products.