Manufacturing technology
medium,” explains Mohsen Habibi, former research assistant at Concordia University and a key member of the team who developed DSP.
Cavitation describes a process whereby pressure variations in a liquid can in a short period of time cause countless small cavities to form and then implode. “These tiny bubbles are famous for their destructive force in many engineering fields,” Habibi adds. He uses the example of propellers on watercrafts, where the continuous stream of bubbles created by the action of the propeller collapse and erode the metal over time. Another example can be seen in nature. When under attack, a mantis shrimp can strike its club with an acceleration force proportional to the firing of a 22-caliber bullet. The strike moves the water so quickly that it creates a low-pressure area and forms a bubble. The bubble then collapses in a burst of high-energy light and sound that is strong enough to almost match the power of the strike itself.
The team at Concordia saw potential in the phenomenon of cavitation and hypothesised that it could be used to drive chemical reactions in certain conditions. “In DSP, we could tame this force in nature to use it for creation, instead of destruction,” says Habibi. He goes on to explain the limitations of light and heat mean they weren’t viable for the specific targeting of energy required for 3D printing. “Therefore, we looked for an alternative route to deposit energy in the remote locations while still being capable of inducing chemical reactions,” he continues. “Sound and specifically ultrasound seemed an interesting alternative since they can pass through objects and also create chemical reactions through the generation of tiny bubbles in the medium, via sonochemistry.”
Printing inside the body
One of the potential capabilities of DSP that is being considered by the team of researchers is printing implants or devices directly into the human body. “Direct sound printing enables non-invasive 3D printing inside the body without an open surgery,” says Habibi. “With this concept, a prosthesis can be created inside the body without the need to hospitalise the patient and perform open surgery, which means a shorter recovery time and less medical expenses. The field of DSP is still at its early stages but has received huge attraction from industries and we hope that soon we can have meaningful progress on that front.” Of course, that’s not to say DSP doesn’t come with its own set of issues. In particular, when it comes to the regulatory considerations and hurdles associated with using DSP for medical purposes, especially when dealing with implants or other
Medical Device Developments /
www.nsmedicaldevices.com
A diagram explaining how direct sound printing uses sonochemistry to create parts.
internal structures. “One of the medical applications of high-intensity focused ultrasound is tumour ablation, which the FDA has approved as a method for treating prostate cancer,” explains Shervin Foroughi, a PhD candidate at Concordia University and part of the research team with Habibi. “Since DSP employs high-intensity ultrasound energy, some of the already existing regulatory considerations of the HIFU ablation can be applied while implementing DSP for in- body printing. On the other hand, the DSP process can be controlled and adjusted with respect to the desired construct to be fabricated at the target. In fact, the application of the DSP for in-body printing is at its early stage, and we believe that regulatory considerations corresponding to the DSP in-body printing should be developed in the future.”
“We looked for an alternative route to deposit energy in the remote locations while still being capable of inducing chemical reactions. Sound and specifically ultrasound seemed an interesting alternative since they can pass through objects and also create chemical reactions through the generation of tiny bubbles in the medium, via sonochemistry.”
Mohsen Habibi
Medical device manufacturing While we may not be using DSP to print directly into the body anytime soon, we may start to see the process being used to create medical devices in the next few years, which is where the research team sees value in the technology right now. Specifically,
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Concordia University
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