Dr. Martin Byung-Guk Jun

Assistant Professor, Department of Mechanical Engineering
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Phone: (250) 853-3170
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Research area: micro to millimeter-scale machine tools and manufacturing systems, and medical applications of solid freeform fabrication techniques

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Research profile:

Building the right home for an in-vitro bone

Dr. Martin Jun is an expert in the engineering challenges of designing machines to fabricate small objects, in the range of few microns to a few millimeters across. He joined UVic’s Faculty of Engineering in 2007, where he founded the Laboratory for Advanced Multi-Scale Manufacturing. His lab has several diverse projects on the go, but these days, Jun is most excited about improving 3-D printing to manufacture scaffolds for growing bone implants.

3-D printing is a type of solid free-form fabrication, which describes a family of manufacturing techniques that don’t use physical molds. In stead, a computer instructs a machine to build the object from a virtual design. 3-D printing machines are similar to a computer ink jet printers, but with this important difference: an ink jet printer applies a pattern of ink onto a sheet of paper, a 3-D printer applies a pattern of adhesive onto a thin sheet of powder, typically plaster or resin. As the adhesive lands, it solidifies the powder to form the first solid cross section of the object. As the printing process continues, a second layer of powder is applied overtop of the first cross-section, and again, a pattern of adhesive is printed, creating the second cross section. This is repeated thousands of times to slowly build up layers of solid material. At the end, the loose powder is removed from each cross section, leaving the 3-D shape. Recently, this technology has found an exciting application in the hot research area of bone scaffolding.

Currently, bone implants are used in many cases where a titanium rod won’t do, most often in dental surgery, but also to modify bones from congenital defects, to replace bone after cancer therapy, and to fuse vertebrae during spinal surgery. The most common source of the bone implant is a bone graft taken, painfully, from elsewhere in the body. But this is sometimes so painful, patients say the cure is as bad as the ailment, and complications can arise at the graft source site. To get around this problem, a new strategy involves growing a patient’s own bone in vitro by placing a few bone marrow seed cells into an in vitro scaffold. The scaffold acts both as a home for reproducing bone cells and a mold for the required bone implant. The scaffold, containing the new growth, is surgically implanted, where the patient’s own bone will attach and engulf the implant, knitting to form a new bone. The scaffolds are made of a biodegradable material that is eventually reabsorbed by the body. Jun favours calcium phosphate strengthened with chitosan (a polysaccharide derived from crustacean shells), a combination that lends itself well to 3-D printing.

3-D printing has been used with particular success for bone scaffolds in human trials by creating scaffolds with a porous surface (the scaffolds resemble sponges) that bone cells seem to thrive on. Jun is working in collaboration with researchers at UBC and Simon Fraser University to improve and perfect this technology. The group is drawing on some diverse skills. It includes a biomaterials engineer (UBC’s Dr. Rizhi Wang), an expert in freeze-drying technology from UBC’s Food Nutrition & Health program (Dr. Tim Durance), and a bionics expert (SFU engineer Dr. Edward Park).

One of the ongoing challenges of bone scaffolding technology is getting the right porous surface for the scaffold. Several groups have tried combinations of micron or even nano-sized pores within larger pores. Jun believes he can better control the porosity, as well as speed up the manufacturing process, by developing an atomized spray mechanism to spray adhesive, replacing the current ink jet mechanism. This would give scaffold builders the option to choose a nozzle diameter and apply a fine spray for fine detail, or course spray for a course texture (or to speed the printing up). For this job, Jun is able to draw on his expertise of designing equipment to make small micron-sized details on larger objects.

So far, Jun has built a prototype for the spray component that can deliver a range of sprays. He is working with Uvic’s Innovation and Development Corporation (IDC) to develop a patent on his design. Next he has to incorporate the component into a printing machine, and work with his collaborators to test the prototype’s ability to build calcium phosphate and chitosan composite bone scaffolds.
One of the team’s goals is to speed up 3-D printing. Currently, it can take a couple of days to fabricate a one cubic inch scaffold; several hours to print and the rest of the time to dry. That is where freeze-drying comes in. Durance is helping Jun incorporate a microwave vacuum drying step into the manufacturing process.

Jun notes that perfecting 3-D printing could have future applications beyond bone scaffolds, such as building scaffolds for other types of organ growth. Beyond tissue engineering, Jun predicts a growing trend of free-form fabrication used to manufacture a host of medical devices. Free-form fabrication techniques were originally perfected as way to make prototypes, the step before an injection mold was made for mass manufacturing. In fact, another name for free-form fabrication is rapid prototyping. However, these techniques are increasingly being used to manufacture the end product as well as the prototype. Jun hopes to create the next manufacturing technology that is miniaturized and energy-efficient enough that manufacturing essentially becomes decentralized. In other words, imagine a surgeon or a dentist using a small desktop manufacturing machine to make custom products on demand.

This model of manufacturing is more likely to work economically when the object is not needed in the thousands. However, there are countless surgical implants, such as hip joints, that could benefit from a surgeon starting the procedure, doing some measurements, and having a direct look at the hip, before fabricating his own joint, perhaps right next door to the surgery. Several of Jun’s projects are working towards this vision of medical rapid manufacturing.