California Institute of Technology's emerging metal 3D printing technology: hydr

Caltech has been doing interesting work in the field of 3D printing for many years, especially Professor Julia Greer and Greer Group. The team is committed to layering, nano, batteries and other new materials, as well as 3D printing processes. A new field that the team has been exploring for many years is related to hydrogel derived materials.

Printing Metal Parts Using Hydrogel 3D

In general, these processes use barrel photopolymerization to produce structures that use hydrogels. These structures are then filled with metal or ceramic precursors, which are converted into final metal components by reaction. In some cases, the team has studied metal oxides, namely zinc oxide, but also the manufacture of electrodes. The researchers' method may be a very fruitful one, because it can rely on standard reductive polymerization processes, such as digital light processing (DLP), stereo lithography (SLA) and mask SLA (mSLA) using standard printers and materials.

Now, Max A Saccone and Rebecca A Gallivan published a paper on Nature entitled "Additive manufacturing for manufacturing microstructure metals through hydrogel injection", and we learned about a new metal printing method. The team used large barrel photopolymerization, especially DLP, to 3D print hydrogels before filling the structure with metal precursors and calcining them, which is a thermal process that will produce metal parts when applied here. The team said that they had produced objects with a size of about 40 µ m and very high hardness. In addition, the researchers believe that materials can be adjusted, and even multilateral parts can be manufactured.

The tested lattice structure consists of about 50 μ M, resulting in a characteristic size of 100 μ M hard parts. The researchers studied nickel, silver and copper, and tungsten niobium, a combination of refractory metals that are difficult to form. They are also able to mix a variety of materials, such as copper and cobalt. A unique feature of this work is that different salts can be placed in different areas from the hydrogel step, and then calcined at the same time. A strange detail is that the hardness seems to be 47% to 15% higher than expected, which may be something to be further developed. Generally speaking, calcination needs to be controlled, which may hinder the industrialization of many geometric shapes. Shrinkage is about 60%, which may also limit geometry and process control.

Indirect metal 3D printing of small parts

By using standard chemicals, no new machines or settings are required and costs are kept low. This may lead to the rapid adoption of this technology by service organizations because they have the necessary equipment and knowledge of some processes. It is also easy to see how companies such as Arcoma or Stratasys' materials department support this approach. Many political parties can unite to industrialize them. In addition, by using barrel photopolymerization, they can use the wave of this technology to produce accurate, tiny details and features. The resulting parts are small and accurate. Perhaps this technology is indeed a very high-performance technology for creating microchannel networks.

Direct write 3D printing and two photon photopolymerization are doing similar work. The other method causes the reduced polymerized parts to be carbonized, thus forming a good conductor. In general, the details related to hardness, refractory and fine beam lattice may be unique.

Now, there are other technologies. HoloAM, MetShape, Incus and Lithoz use what I call a "slurry SLA", where the resin is preloaded with metal particles and then printed using a reduced photopolymerization system. Then degrease and sinter the parts. Of course, this requires many steps, and the part size of slurry SLA is not large. Sintering can also cause shrinkage problems. However, for some geometries, the slurry SLA can produce detailed parts with good internal surface texture (because the resin is the support and washed off). For larger parts, adhesive spraying is a high-yield and low-cost technology. One can also consider the combination of lost wax casting and reduction photopolymerization. For small parts, material extrusion or powder bed fusion may not be considered. However, there are some micro processing and printing technologies that may be competitive.

Source: Yangtze River Delta Laser Alliance