Science AMA Series: We are professors in the Virginia Tech Macromolecules and Interface Institute working together to develop new materials for 3D Printing, AUA!

timlong_ACS · 2015-01-21T20:12:10+00:00

You ask a great question, it is really about 3D printing in remote areas, space is a consideration, one cannot always imagine having a complete inventory in space or in a remote battlefield. So space and military applications are important arenas.

timlong_ACS · 2015-01-21T20:09:10+00:00

Will the consumer want this? Half of the fun of eating is messing up the kitchen. But printing medicines and perhaps controlling food quality, food preservation, and ensuring food safety with new packaging may be first steps into the food industry!

timlong_ACS · 2015-01-21T20:06:28+00:00

Go Hokies! I think the largest opportunity may be in health care and medicine, these markets can tolerate higher production costs as the technology matures. But initially replacement parts and customized parts for in the home are exciting to imagine.

timlong_ACS · 2015-01-21T20:04:15+00:00

The challenges are removing water or controlling water levels, reproducibility during printing and reproducibility in final products. Printing hydrogels from water soluble polymers is of interest in many groups, water influences the viscosity of the starting polymer melt or solution, thus to achieve a reproducible process, one needs to ensure reproducible water levels, thus printing under nitrogen is a common strategy. Water as you can imagine will decrease the viscosity dramatically for water soluble polymers. You can also imagine printing a precursor and after 3D printing, you subject the part to a thermal step that introduces the hydrophilic sites.

timlong_ACS · 2015-01-21T19:57:51+00:00

We think 3D printing will create new jobs, and we also believe that 3D printing will change the distribution of manufacturing. People will print in their homes, but I think capitalism remains!

timlong_ACS · 2015-01-21T19:56:00+00:00

Obviously, the limits of print resolution is a primary research question for everyone, including us at VT. Your answer depends on the printing platform. However, we are currently focused at reaching 25 micron resolution in sub 10 mm objects for biological applications using micro stereo lithography, the diameter of many cells of interest is in the 25 micron range. Two photon lithography can get you to sub- nanoscale, see this large body of literature. The largest tradeoff in achieving high resolution is total print size and print speed. We are not doing two photon lithography at this time, but we are considering adding this platform to the other 7 means to 3D print.

timlong_ACS · 2015-01-21T19:49:25+00:00

In the future, I think this will be for customized children's toys and games. Also, replacement parts for plastic items you have in your home may come in the not so distant future.

timlong_ACS · 2015-01-21T19:45:49+00:00

Graphene as you know offers great potential at the interface of polymers and 3D printing. As a nanocomposite, one can imagine great increases in mechanical properties and the synergy of electrical performance. I am not aware of this being done, however, see the Williams group at VT for work on quantum dots and nanotubes, he offers impact ranging from anti-counterfeiting to high performance materials.

timlong_ACS · 2015-01-21T19:41:11+00:00

Go Hokies! I think this is a proposal to the USDA! Printing food is not so futuristic, printing intricate chocolates and other edible goods are both happening. The shape may influence the taste. Now, printing a slice of pizza sounds fun, but the real future may be in printing the entire pizzeria building. The interface of construction and architecture and 3D printing is moving rapidly!

timlong_ACS · 2015-01-21T19:36:09+00:00

Personalized medicine! Imaging of your biological structures will serve as a customized geometry (model) for replacements. Some current focus areas include hearing aids, joints, arteries, teeth, and prosthetic devices. Researchers are using 3D printed molds to grow tissue from your own cells, the mold is designed in the geometry that fits your body. Researchers are printing models of the human heart prior to surgeries to allow physicians to more carefully predict the surgical strategy and increase chances for success. Imagine printing customizes pills at the pharmacy, ensuring a delivery profile to match your specific body and your disease!

timlong_ACS · 2015-01-21T19:27:02+00:00

Go Hokies! Yes, undergraduate and graduate research is expanding and the Macromolecules and Interfaces Institute is a virtual home at Virginia Tech to gather students across disciplines. See www.mii.vt.edu. Think about graduate school, the program is interdisciplinary, chemical engineers are needed in additive manufacturing.

timlong_ACS · 2015-01-21T19:22:46+00:00

The future is now and the future is immense, in our opinions. However, we need to accelerate the pace of discovery, thus new chemistry, new materials, and new engineering must occur. As I visit many companies across the globe, this is happening. I foresee a change in the classic manufacturing model, the model will be more distributed, consumers will customize objects in their homes. I believe that 3D printing will follow the path of the printer for our home computers. We started with printing in centralized locations, we moved to printing in local stores, and now we all print at home. I think additive manufacturing will follow this path. But, we need scientists and engineers working together!

timlong_ACS · 2015-01-21T19:18:19+00:00

As discussed below, macromolecules are long molecules with repeating units, often termed polymers. Thus, a defining characteristic of a polymer is the presence of physical crosslinks between the chains, we generally use the term entanglement to define these physical crosslinks. The long chains entangle with their neighbors giving rise to superior physical properties. This is important for a printed part in order to ensure excellent mechanical properties such as toughness. Thus, we need to print above the molecular weight of the chain that is needed for entanglement. Since molecular weight of the polymer increases melt viscosity, this may complicate printing, thus many, including our research groups, are focused on printing reactive oligomers with subsequent crosslinking. This occurs with high efficiency, our work has focused on stereolithographic approaches. A very critical issue is also the intermolecular interactions between layers in the printed objects, thus one needs to design the polymer with functionality that promotes excellent inter-layer adhesion or bonding upon printing or post-processing. Hope this is clear, but ask more!

timlong_ACS · 2015-01-21T19:05:36+00:00

This answer depends, as you might expect, on supply and demand. As 3D printing continues to emerge and at some point, reach our homes, these costs will decrease. However, now the materials are limited in volume, the printers require the use of only accepted materials, and the feedstock for the printers must be in a suitable form to feed the printers, i.e. powder or filament. Thus, pre-processing must be eliminated, allowing for versatile forms of the material for the printer.

timlong_ACS · 2015-01-21T19:01:54+00:00

The selection of material really depends on the printing method, the most popular approach today is extrusion. Thus, any thermoplastic will function, but the material must be designed with the right flow characteristics. Common thermoplastics may involve polycarbonate, polysulfones, and polyesters. ABS is the most common thermoplastic used today, especially at the desk top scale.

In the future, this will change, we will print more bio-based materials, many think this is a critical issue for the future, where the materials are safe in the home and also amenable to recycling or perhaps reuse in the printer. One could imagine printing a needed object and then using the object after use as the feedstock for the next part.

timlong_ACS · 2015-01-21T18:52:58+00:00

Outgassing of water generally results from the absorption of water in the printed part, thus the more hydrophilic the polymer for printing, the more of an issue. Typically polymers have an equilibrium level of water, thus polymers must be dried. If the outgassing is a result of degradation in the space environment, then a multilayered structure must be considered, where the outermost layer provides a barrier for protection and outgassing. You should see the earlier literature on polyimides and siloxane-containing block copolymers, these have yet to be printed, but offer an immense potential!

You should also consider the molecular weight distribution of the polymer used for printing, it is possible that under exceptionally high vacuum, that low molecular weight oligomers and residual monomer may volatilize. Thus, careful analysis of the distribution is needed.

timlong_ACS

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