Designing and printing a device to change over time—4D printing—helped the University of Michigan’s CS Mott Children’s Hospital save three very young lives. Born with tracheobronchimalacia (TBM), which causes the windpipe to collapse and prevent breathing, all three faced what could have been a short, difficult life.
Using a combination of medical and engineering skills, the Michigan team built a splint that would hold the airway open, prevent outside compression of the airway, and bend and change as the child grew. Eventually, the splint would be absorbed when its crucial job was completed. Using 3D printing, each splint was designed specifically for each patient. Designing the splint to change over time makes these the first 4D-printed devices not only used in a patient, but shown over three years to successfully do exactly what they were designed to do.
With TBM, if the child can be supported through the first 24–36 months, growth generally results in a natural resolution of the disease. Using the US Food and Drug Administration’s emergency exemption for devices, the Michigan team set about developing a device that would meet all performance requirements while not causing adverse tissue reaction. The concept device was an open, bellowed cylinder with 10 design variables allowing placement of the splint around the collapsed airway via sutures through small holes.
To personalize the device for each patient, the team began with multidetector CT imaging of each patient. The images and parameters were input to proprietary software to generate the bellow waves and design to submillimeter accuracy. The splint design was placed over a 3D model of the patient’s airway for validation. Mechanical performance of the design was ensured through finite element analysis.Read more