Engineering Inside:

2015 Issue 2
3D Printing

Meet Dr. Scott Hollister!

May 2015
Dr. Hollister

Dr. Hollister
University of Michigan Health System

Dr. Hollister is a Professor of Biomedical Engineering and Mechanical Engineering at the University of Michigan, where he directs the Scaffold Tissue Engineering Group (STEG).  Dr. Hollister and his collaborators have designed and developed a variety of medical devices utilizing 3D printing, an area in which he has worked for 17 years, publishing his first paper in 1997.  He and his colleagues first developed an approach for laser sintering for polycaprolactone in 2004.  His general research focuses on the design, fabrication and evaluation of biomaterial platform systems for tissue reconstruction. He is a fellow of the American Institute of Biological Engineering. His work on a bioresorbable tracheal splint along with Dr. Glenn Green was given a Popular Mechanics 2013 Breakthrough Innovation Award.  This implantation of this 3D printed device to save the lives of three children has been featured on the Today Show, the New Yorker, USA Today, NPR, Time magazine, Nature, Science, and Popular Mechanics among other media.

1. You have an interesting background!  How does the work you do involve your aerospace/mechanical and biomedical engineering backgrounds?

At a fundamental level, all engineering disciplines share a common root, basically mathematics, the sciences (physics, chemistry and biology), and now especially a knowledge of some type of computer programming.  Skills I learned in aerospace/mechanical engineering like solid mechanics, numerical methods, and computer programming I use in biomedical engineering.  Although we don’t often think of them this way, biological tissues like bone, skin, and cartilage have mechanical properties and behavior just like engineered structures including concrete, synthetic rubber, steel, etc.  Therefore, I use this type of background from aerospace/mechanical engineering in biomedical engineering.  This is why it is important to learn the fundamental sciences and mathematics, as well as some level of computer programming.

2. How did you first get involved with 3-D printing?  Do you create 3-D printed items for fun?  And, how is this integrated into the work you do?

I first became involved in 3-D printing in the early to mid 1990’s when a mentor of mine, Professor Noboru Kikuchi, developed a method to design optimized material layouts that produced very complex structures.  He mentioned that he was looking at 3D printing, because it was the only method capable of manufacturing these complicated material layouts.  I had started working in tissue engineering and regenerative medicine (the study of regenerating or helping to make new tissues) at the time in the area of designing and making materials called “scaffolds” which are 3-D structures used in tissue engineering to deliver and support cells.  These scaffolds can have very complex geometry including a porous structure.  I thought to myself that 3D printing could be used to manufacture scaffolds as well.  My research laboratory and I started working on the use of 3D printing to make scaffolds, and we published our first paper on this idea in 1997.

3. You and a cohort developed a 3-D printed device that helped saved a baby’s life – tell us how this came about and why 3-D printing made the difference.

Hollister and Green

Hollister and Green
University of Michigan Health System

Dr. Glenn Green (the pediatric Otolarnygologist with whom I developed the airway splint) and I were brought together by a colleague at the University of Michigan.  Dr. Green is a specialist who has developed surgical techniques for complex airway reconstruction in children.  He had an interest in applying tissue engineering technology to airway reconstruction.  My laboratory and I had developed image-based techniques (for designing structures such as scaffolds) and 3D printing of polycaprolactone (a type of resorbable, biocompatible plastic) for a variety of applications, especially in tissue engineering.

Video credit: University of Michigan Health System

We were initially interested in tissue engineering an entire trachea, a very challenging endeavor. The trachea is sometimes called the “windpipe” and it is a tube that connects the throat to the lungs, allowing air to pass for breathing. I mentioned that I thought it would be best to do this in a step by step manner, much the way that NASA developed the Apollo program to go to the moon by first developing the Mercury program to work out how to launch vehicles and humans into space, then the Gemini program to work out how to locate and dock space vehicles and finally the Apollo program (my aerospace background coming into play).  So we thought we would develop the scaffold first for the airway, then work on how to add cells to regenerate the tissue.  Dr. Green then said he felt that even the scaffold alone could address a very challenging problem he faced with kids, and that was tracheobronchomalacia (a long term meaning softening and collapse of the trachea and bronchi – that is the airway).  That is how we started work on the tracheal splint.

3D printed splint with suture holes

3D printed splint with suture holes
University of Michigan Health System

The geometry of the splint was itself complicated.  It had multiple suture holes (holes thru which a surgical needle and ‘thread’ could be passed to secure the splint with ‘stitches’) and we designed the splint based on digital models we made from CT or MRI scans of each individual patient.  This meant that the design could change with each patient.  Therefore, due to the complex 3D geometry and the patient specific nature of the splint, we needed to use 3D printing.

4. What do you love about blending technology and medicine?

At one level, the human body (and any animal body) can be thought of as very complex machines, perhaps the most complex machines that exist.  Bodies have mechanical structures, chemical structures, electricity, nanotechnology, Multiscale structures, etc.  Medical doctors have a very complex job to treat this very complex machinery.  I believe that technology and engineering can make and has already made great advances for medicine.  To design and develop devices and technology to diagnose and treat disease and trauma requires a great deal of engineering.  You see this in many of the great advances in medicine from CT and MRI scanners to joint replacements to minimally invasive surgery to name just a few.  It is always exciting to come to work and think about how we can develop new devices to help patients.  3D printing will greatly expand the types of devices we can make, from external devices to internal implants, and even 3D printed cells and tissues.  It is exciting to have these 3D printing technologies available that allow us to make our designs and ideas into a physical structure in a matter of hours and days as opposed to weeks and months.

5. What do you think are some of the future applications for 3-D printing in general, and for medicine in particular?

A model of Garrett's trachea, along with splints similar to those used in the operation. Juliet Fuller/University of Michigan Health System

3D printed trachea model and splints
Juliet Fuller/University of Michigan Health System

Definitely you will see more 3D printed patient specific medical devices and implants.  In fact, in five years, I believe that most academic and high level medical centers will have their own 3D printing centers and engineering staff to design and 3D print devices and implants for those difficult and uncommon cases for which an “off the shelf” implant or device won’t work.  Complex surgeries will routinely be planned and practiced on 3D printed models before they are done on the patient.  In fact, patients will be drawn to these centers to have this personalized medicine and surgery over centers that do not have these services.  Finally, you will also have the capability to print cells (that is being done now) to create live tissues in the lab on which to test drugs and procedures, in addition to being able to implant into patients.

I think in general for 3D printing, you will see more “at home” printing.  Just as now we have computers and the internet in our homes, something that would have been unheard of in the 60’s and 70’s when only large companies, academic centers and the government had large mainframe computers, a 3D printer will be just like a laptop computer in the home.  You will see more personalized items and devices for the home, just as we have the advent of personalized medicine.  Furthermore, whereas computer literacy and programming was the domain of educated specialists in the 60s and 70s, but now is taught in elementary schools, the same will happen for 3D printing and Computer Aided Design techniques needed to create the design for items we will 3D print at home.

6. Is there anything you don’t like about blending medical and technology applications?  Challenges?

I wouldn’t say there is anything I don’t like about blending medicine and technology, but there are significant challenges.  First and foremost is that as a professor you always need to be writing proposals and trying to raise money to support research.  We constantly worry about having money to support and train our graduate students and post-doctoral fellows, as well as to purchase equipment to do work.  This can be especially challenging in 3D printing, where sophisticated machines can easily cost over $100,000.  I think another big challenge is that even though you can blend technology and medicine initially in research, getting the technology to the patient can be a long and expensive road.  It is therefore a challenge to not think narrowly about just the science/engineering/technology, but also about what the end problem is that you are trying to solve, the regulatory issues for the device you trying to make, and the business aspects of getting the device/technology into clinical use.  Finally, just the breadth of knowledge to work on interdisciplinary endeavors like medical 3D printing becomes more challenging every day.  I often find myself regretting that I don’t have a better understanding of fundamental issues like chemistry and materials science that are important to advancing this field.  That is why I would really like to emphasize these issues to students.  Also, I think often times we as educators don’t give students enough of an insight and motivation as to why they (the students) should learn fundamental STEM topics.  For example, how often do we tell students that the video games that they are playing are really enabled by the mathematics that goes into computer graphics, the quantum mechanics fundamentals that went into the development of microchips, and even ideas of heat transfer that go into designing the cooling systems that enable the powerful computers that can run the sophisticated video games?

Video credit: University of Michigan Health System

7. How have the development of computers and software impacted the engineering and medicine work you have done over the years? 

Computers and software advances have had a tremendous impact on the work I have done over the years.  The increased computing power available (ala Moore’s law) and memory capability have allowed us to work with and create patient specific models from huge image databases.  We can also perform much more sophisticated design simulation in a much shorter time.  These types of advances play directly into 3D printing, as the designs we generate for patient specific devices begin with patient image data, which can be a tremendous amount of data.

8. Are there any new initiatives you are focusing on that apply 3-D printing to support surgery, medicine, or healthcare? 

We are working on ideas of how to make 3D printed models more mechanically realistic to mimic tissue properties to enable more realistic training and simulation for physicians.  We are also always working on designs for new implants, and try to expand the range of biomaterials that we can utilize with 3D printing systems.  This is a critical need for 3D printing, to expand the material repertoire that we can use on these systems.

9. Whom do you admire and why?

I would have to start with my late father Ernest Hollister.  Although he never went to college, he had a tremendous interest in technology and science.  I took many trips as a kid to NASA, national parks, etc.  He instilled in me the wonder and fascination with learning new things and learning about science and technology.   I also admire in general people that challenge to push ideas forward, and are will to suffer a great deal to push ideas forward.  That have a vision for what can be.  I have often heard it said that scientists look at the world and say “Why?” while engineers look at the world and say “Why Not?”.  I think that spirit, trying to advance ideas in the face of long odds and sticking to it is very admirable, especially as I feel it difficult to do myself many times.  People like Tesla, Edison, the Wright Brothers, Lister, Vannevar Bush, Wozniak, Jobs, and many others who had great visions and went through a lot to see them fulfilled, and in many cases never saw their visions fulfilled in their lifetimes.  Finally, I would like to say that I admire today’s middle and high school students like my sons.  Their world that they are growing up in is expanding so rapidly and they are faced with learning so much new knowledge, that it is a great challenge.  They face much greater pressures and competition growing up, and I admire how they deal with these challenges.

10. Is there a particular application or industry that you think could benefit the most from 3-D printing advances in the next few years? 

I am obviously biased, but medicine and the healthcare industry, and patients as a result, will benefit tremendously from 3D printing.  As I mentioned in an earlier question, patients in the future will routinely be able to get devices, implants, and even material/cell composites designed especially for their anatomy and conditions.  I think 3D printing will also expand the range of healthcare into underserved regions, as 3D printers become cheaper and the range of materials becomes greater for 3D printing, you will be able to send devices for a few patients to every corner of the world.

The other area will be at home applications and businesses, as individuals can make their own gadgets and devices at home, or through third parties like Shapeways (, an online service that works with individuals who design 3-d products on their own computers, and upload to build and sell.

Video credit: Shapeways

11. What’s the most gratifying aspect of your work?

I would say that there are two aspects of my work that are most gratifying.  First and foremost, is to see that work we have done help people and literally save lives.  No matter what you achieve in your career, how much money you make, or how many awards you win, nothing is better than contributing to an improvement in someone’s life.  Second, the ability to interact with so many intellectual colleagues and to learn new ideas every day makes the work very stimulating and exciting.

12. What advice would you give to students interested in learning more about 3-D printing applications?

First of all, I would suggest that students study the fundamentals, math, the sciences and computer programming and modeling.  All of this background is important for fully utilizing 3D printing.  You have to be able to make the designs that go into the machine (requires math, physics, and computer modeling/programming), but you also had to understand material science and chemistry so that you can make/adapt the materials to the 3D printing systems.  Finally, 3D printers require control and mechanical/electrical devices.  All of these issues are important for 3D printing, as well as enjoying the “cool” aspect of it.

13. If you weren’t working in medicine, what would you be doing?

I would say that if I weren’t in biomedical engineering, I would be doing some other type of engineering, likely in the aerospace and automotive industry.  In many ways, what I would be doing then would be much different, but in some ways the design, modeling and 3D printing work would be very similar.  This goes back to my original comment that all branches of engineering share some common roots like mathematics, the sciences and computer programming.  However, I would also like to make a plug for the humanities.  As I believe that understanding the humanities and the arts, in addition to science and technology, is important for being a creative person.

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