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Industry Insights|Harvard University Studies on Multi-material 3D Printing Technology Allowing Fast Filament Switch

Researchers at Harvard University's Wise Institute have developed new technologies for multi-material multi-nozzle 3D (MM3D) printing, which supports high-speed pressure valves for fast, continuous, and seamless switching between up to eight different printing materials. This new technology can be applied to the printheads of a single nozzle or large multi-nozzle array for free switching of multiple materials during 3D printing.

Multi-material 3D printing, Fast Filament Switch at 50 Times per Sec
The 3D printheads themselves are made by 3D printing technology, enabling quick customization and convenient application in the factory. Each nozzle can switch materials at such a fast speed 50 times per second that eyes cannot even catch up the process. MM3D printing technology can also be used to create more complex objects, such as robots.

The team designed and 3D printed a soft robot consisting of rigid and soft elastomers shaped like a milliped which is composed of embedded pneumatic channels that soften the soft "muscles". The flexible structure enables the robot to "walk", moving about half an inch per second with a load eight times its own weight, and can be connected to other robots to withstand greater loads.

Jennifer A. Lewis, Sc.D., the corresponding author, is a core faculty member at Harvard's Wyss Institute and a professor of bioinspired engineering at Hansjrg Wyss. “This approach enables rapid design and manufacture of voxels,” she said. “This is an emerging paradigm in the field of 3D printing. With multiple functions, structures and bio-inks, we can now seamlessly integrate different materials on-demand into 3D printing process.”

Professor Lewis, the researcher who is involved in this research, stressed that there has been a long way to go because the ultimate goal of this fast, accurate multi-nozzle 3D printing technology is to print biological tissues and organs. Professor Lewis is working on the extrusion of 3D printed materials and biomaterials. One of the major limitations of 3D printing of advanced organs is the ability to use hydrogels to replicate complex material structures, including blood vessels, without compromising cell viability.

The current limitation is that the current MM3D printheads can only print the same part repeatedly. However, with the development of MM3D printing technology, it will eventually create nozzles that can squeeze different filaments at different times, and smaller nozzles to achieve higher resolution, and even larger arrays can be used in various sizes and resolutions. Make fast 3D printing.

Multi-Material Multi-Nozzle 3D (MM3D) printing technology enables inter-switch between up to eight different filaments per second for 50 times, creating complex high quality for a fraction of the time currently required for other extrusion-based printing methods 3D object.

Most 3D printers can only use one material at a time, while inkjet printers capable of multi-material printing are limited by the physical conditions of droplet formation. When using a conventional squeeze 3D printer, the time required for printing is proportional to the size of the target model because the print nozzle must move in three dimensions, not just one dimension. The MM3D's ability to quickly switch between multiple nozzles and multiple inks eliminates the time wasted to switch printheads and helps convert geometric times of print time into linear growth for faster printing multi-material 3D model.

Multi-nozzle printhead, Each Nozzle Supports Eight Different Types of Filaments
The key to MM3D printing to quickly switch inks is a series of Y-shaped tubes in the printhead, with multiple filament channels merging together at one output nozzle. The nozzle shape, print pressure, and filament viscosity are accurately calculated and adjusted so that when pressure is applied to one of the junction points, the downward flow of filament prevents another split filament from entering and flowing backwards, which prevents the filament from mixing and maintaining a single material for the 3D printed object. By operating the printhead with a row of fast pneumatic valves, this one-way flow feature quickly switches the filaments of multiple materials that flow continuously from each nozzle and can be used to construct a variety of material-compliant parts.

Dr. Jochen Mueller, co-author of the paper, said: "With MM3D technology, people can use reactive materials with properties that change over time, such as epoxy, silicone, polyurethane or bio-ink, and easily integrate materials with different properties together, to create an origami-like structure or a soft robot that combines rigid and flexible parts.

To prove their study, researchers 3D printed a Miura origami structure that was joined by a rigid "panel" section to a highly flexible "hinge" section. Previous methods of constructing such structures required manual assembly of them to form a stack. The MM3D printhead is now capable of continuously extruding two alternating epoxy inks using eight nozzles, step by step, and the stiffness of these inks differs by four orders of magnitude. The hinge 1000 was damaged after multiple folds, indicating a high-quality fit between the printed hard material and the flexible material.