Story by Erik Potter  ♦  Photos by Monique Woo

Tucker sits on the ground, and looks at the camera, which is at eye-level.
Tucker, a 6-year-old Australian Shepard, was born with four legs and three feet. Mizzou’s 3D Printing Club has worked for more than a year to design a prosthetic foot for him.

Kendra Earl Warlow is driving to a dairy farm in rural Missouri. She is a Mizzou undergraduate far from her Pennsylvania home. She’s unsure what she will find at the end of her hours-long drive, but she knows what she is looking for: companionship.

A friend of a friend is giving away a litter of puppies, and Warlow wants one. When she gets to the farm, only one remains. She walks up to the pen where he is kept, looks down, and sees an 8-week-old Australian shepherd. He has four legs, three feet and big, soft eyes. Her heart melts.

Kendra, left, sits on the ground and smiling at Tucker, who stares straight ahead.
Kendra Earl Warlow adopted Tucker when he was 8 weeks old. “He’s my best buddy,” she says.

“It was just Tucker and me for a while,” says Warlow, who is now in market development for the startup firm Paytient. She has an ebullient personality and a quick smile. Dog and student go on to navigate her animal sciences degree together. Tucker is a comfort to her when she doesn’t get into veterinary school. He’s there for her when, instead, she goes through a master’s degree program in agricultural applied economics in the College of Agriculture, Food and Natural Resources.

When Warlow is writing her master’s thesis, Tucker is four years old. His missing paw has never stopped him from doing anything he wanted, but the extra strain the absent foot puts on his body has taken a toll. His back and hips are getting sore and painful to the touch.

Warlow investigates what she can do for him. A prosthetic would help, but it would cost thousands of dollars — money she doesn’t have. But in her research, she learns that prosthetics can be made by 3D printers. Sitting in Ellis Library one day, writing her dissertation, she glances over and sees a 3D printing station. She runs over.

“You wouldn’t be able to make a foot for my dog, would you?” she asks.

Something that means something

At the same time Warlow realizes she needs a prosthetic foot for Tucker, the student-run 3D Printing Club is looking for a new project. The club president at the time, Nick Bira, is working the 3D printing desk at Ellis when Warlow rushes up with her question.

Previous 3D Printing Club President Samuel Donovan, Andrew Dove and Kendra Earl Warlow pose with Tucker.
Previous 3D Printing Club President Samuel Donovan, current club president Andrew Dove and Warlow pose with Tucker.

Bira agrees to take the idea to the club, where it catches the interest of Andrew Dove, then a freshman mechanical engineering student from Columbia.

Dove is still trying to find his fit in the engineering school. “Coming to Mizzou, I thought I wanted to be a boat mechanic,” says Dove, who was interested in naval architecture. “I didn’t even know what mechanical engineering careers were out there.”

He sees the 3D Printing Club as a way to explore the field, make friends and, in the case of Tucker, do “something that means something.” Even as a freshman, Dove is thinking big-picture. When he graduates, he says he wants to have a good answer to the question, “What did I do that people will remember me for?”

Layer by layer

There are many types of 3D printers. The general concept, however, is the same.

3D printers build objects in layers. The machines extrude a thin layer of hot material — often a type of plastic, but a variety of materials can be used — onto a plate in a precise pattern. Each subsequent layer melts with the layer below so that the object takes shape from the bottom up. An inch-tall item might be composed of 170 layers, though settings can vary widely. A computer file, called the Gcode, tells the machine where each layer goes.

You can find free files online for printing simple items such as a planter or a vase. Designing a file yourself is much harder. And it’s another matter entirely to design an object customized for an individual dog that you want him to walk, run and jump with.

Try, try again

When Dove first meets Warlow and Tucker in 2017, he knows right away this project will be different from the personal printing projects he has done in the past.

“When you have people depending on you, your timeline is a lot shorter,” he says.

Dove leads the project, but a team of club members help. First they take pictures of Tucker to see how he stands. They use calipers to measure the length of his leg and the length of his existing hind foot. Then they started designing.

Andrew Dove holds a caliper up to Tuckers right rear leg to measure its width. Kendra Warlow holds Tucker's leg still.
Dove makes a measurement of Tucker’s leg during a prosthetic fitting.

The first prototype they produce is a thick plastic brace with a flat, grippy bottom. It straps to Tucker’s limb. “It was really clunky,” Dove says. It is also difficult to put on and too heavy for Tucker to use. They scrap it almost immediately.

Dove reaches out to the local office of Hanger Clinic, a prosthetics and orthotics company. Gary Lenzini, a clinic manager there, agrees to help them. The club’s second design is much closer to the mark.

Instead of a brace that straps on, they make a socket that Tucker’s leg can settle into. A strap around Tucker’s back acts like a pair of suspenders to keep the socket on.

That winter, Warlow, Tucker and the 3D Printing Club meet in the club’s Noyes Hall office to try the second prototype.

Closer to the mark

“Guys, this looks awesome!” Warlow says when she sees the small, blue plastic foot the team has designed.

Dove pushes the blue plastic prosthetic foot under a band saw.
Dove carves off a piece of Tucker’s prosthetic foot with a band saw.

Dove has a calm and measured bedside manner. He talks Warlow slowly through the design decisions the team has made, where he hopes the new prototype has improved and where he thinks it might still fall short.

Then, Warlow holds Tucker while Dove slips the prosthetic on. Or tries to. The opening isn’t quite right, and Tucker isn’t putting any weight on the leg. They take it off and try again. Same result.

The socket is too tall, Dove decides. He grabs the blue foot, takes it to the back room, puts it on the band saw and carefully carves a chunk off the top.  

“The biggest challenge with a dog is you can’t ask him how he feels,” Dove says. But dogs will tell you with their actions, and they’re always honest.

Dove comes back into the room, puts a racquetball on the end of the foot to increase its stability and puts the foot back on Tucker.

They aren’t using the suspender yet, so the foot isn’t secure enough for Tucker to walk on, but — for a moment — a dog that has never had a right rear foot in his life puts his full weight on both of his back limbs.

Shot from between Tucker's front legs, Dove, leaning on the floor, tries to fit the foot prosthetic onto Tucker. Earl, standing, holds his leg still.
Dove and Warlow assess what changes need to be made for Tucker’s prosthetic leg.

99 percent done

Over the next year, the team continues to iterate. They are now “99 percent” done with their seventh and final design.

Gone is the single-piece blue-plastic socket. It looked elegant, but it wasn’t functional enough.

Instead, the team has engineered a much shorter socket with two armatures that fit snugly on either side of Tucker’s leg. Instead of a suspender, they use a self-adhesive medical wrap to secure the device to his leg.

The inside bottom of the socket is filled with a gel cushion to make it more comfortable for Tucker to use. And instead of a racquetball, they glue a rubber squash ball to the bottom of the foot, which is more slip-resistant.

Also, in the new design, the ball is directly underneath the socket, not off-center, which had caused Tucker to rock back on his heels. “That was something we learned about in statics class sophomore year,” Dove says.

Dove, standing in front of 3D printing machines, holds two foot prosthetics for Tucker.
Dove holds the two latest prosthetic prototypes for Tucker. The red foot has pivoting armatures for maximum flexibility. The white foot has fixed armatures for maximum stability. Photo by Erik Potter

Tucker was able to use a previous prototype, one that had a foam ball painted with rubber. They discovered that the rubber paint flecked off when it was used in the real world, which made it too slippery.

The previous prototypes all sit in a box in the club’s new offices in the basement of Lafferre Hall.

“It feels almost silly that we started with that,” says Dove, holding the original bulky prosthetic. It resembles a pipe wrench. “But you have to start with that initial hypothesis and refine it.”

In the past year, the number of club members interested in prosthetics has grown. Ten students regularly attend project meetings. They’ve even taken on a new project — a partnership with a nonprofit, Aarogya Seva, that is providing low-cost 3D-printed prosthetic hands in India.

With the help of Tracy Ell, founder of Hitek Limb & Brace, a Columbia-based prosthetics company, the club is engineering a limb that can be produced for $300. They plan to raise money from local businesses to fund production so they can supply the hands to Aarogya Seva for free.

Fills the soul

The Tucker project confirmed a lot of things for Dove, who hopes after graduation next year to get a job in the biomedical industry. This summer he will complete a second internship at Corelink Surgical, a St. Louis-based company that designs spinal implants.

“It reinforced where I’m going and the decisions I’ve already made,” he says.

As for Warlow, she is effusive in her praise.

“It’s such a joy to know all these other people are as invested in Tucker as I am,” she says. “It fills up my soul.”

Warlow puts his nose up to the camera lens.
Tucker is “super curious — but with a tentativeness,” Warlow says. He loves to go on hikes. He wore a recent prosthetic the 3D Printing Club made for him so much that the traction-giving rubber paint on the bottom flecked off.
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