BOSTON -- Leon McCarthy is just like many other 12-year-olds. He loves sports and cool technology.

The difference for Leon is that cool technology has allowed his family to use a 3D printer to create a prosthetic hand that they otherwise couldn't afford. And, with that hand, Leon can catch a football.

Leon showed off the third iteration of a hand made of $5 in plastic material at the opening of 3D printer company MakerBot's second retail store in Boston on Thursday.

12-year-old Leon McCarthy shows off his 3D printed hand, which cost about $5 in materials to make on a MakerBot 3D desktop printer

Due to a congenital birth defect, Leon has no fingers on his left hand. Until recently, doctors told his family he shouldn't even consider a custom-engineered prosthesis due to the high cost -- $10,000 to $80,000 depending on quality.

About a year and a half ago a friend of Paul McCarthy, Leon's father, purchased an industrial 3D printer for his product design company. He told McCarthy he believed it could be used to create an inexpensive prosthetic hand.

3D printing (also known as additive manufacturing) works by laying down consecutive layers of materials -- plastics, ceramics or metals - from the bottom up to create an object. The printable objects, created in a computer-aided design program, are sliced into many layers by another computer program, which tells the printer head where to deposit materials on the printer table.

CAD designs, which come in the .stl file format, are abundant on the Internet and can be downloaded mostly for free. The .stl format stands for stereolithography -- using an image for object fabrication.

Paul McCarthy downloaded a free design for a "Robohand" posted on Thingiverse, the most popular website for sharing CAD files. With that, and about $150 in parts, Leon's first prosthetic hand was printed.

South African carpenter Richard Van As, who'd worked with Ivan Owen, a special effects artist and puppeteer in Bellingham, Wash, created the original prosthetic hand blueprints.

Van As had accidentally cut off his fingers on a table saw and found Owen after viewing his YouTube video about developing a mechanical puppet hand.

The original prosthetic hand design was functional but not aesthetically polished.

"We called it Frankenhand, because it had bolts and screws sticking out of it," Paul McCarthy said.

Earlier this year, National Public Radio published a story about young Leon's first printed hand. The article caught the eye of Bill Sullivan, a science teacher at a charter school near the McCarthy's hometown of Marblehead, Mass.

Sullivan had recently used a grant to obtain a MakerBot desktop 3D printer the McCarthy's they could use the machine to create new prosthetic hands.

Due to a congenital birth defect, Leon has no fingers on his left hand

Working with others in the Google Plus prosthetics development community, e-NABLE, Paul McCarthy has improved the prosthetic hand's design and printed out the second iteration that requires about $5 in plastic materials.

Today, Leon is using his third generation hand. Each new version offers him more motion and capabilities.

Paul said work is now underway on making an articulating thumb and more rounded knuckles to get a better grip. He's also designed a 3D printed cuff for his son's forearm to replace the soccer shin guard they were using to attach the hand. The ultimate goal, Paul said, is for his son to be able to tie his own shoes using the prosthetic hand.

Leon's got his own ideas. "I want to put a laser on it and a pencil sharpener," he said.

MakerBot has also helped the McCarthy's redesign the prosthetic hand so that instead the screws used in the original "Frankenhand," it snaps together; There's a bit of hot glue and duct tape to keep it all together under pressure.

Fishing line is used to give the fingers action. The line runs through channels in the fingers secured with a knot at the tip of the finger on one side and to a base toward the elbow side of the device. "Thin bungee cords run through the top of the fingers and secure at the knuckles to return fingers to open position upon release," Paul McCarthy said.

There are multiple parts to be printed. Each of three or four printings takes one to two hours. With a bit more experience, Paul McCarthy believes he could produce more parts in a single print, reducing the number of printing jobs to one or two.

MakerBot, whose founder created the Thingiverse website in 2009, has been key in enabling designs to be uploaded for others to use. Since Thingiverse was created, more than 150,000 CAD designs, from toys and mechanical parts to medical devices, have been uploaded to the open website by "makers," the 3D printer user community.

Meanwhile, MakerBot is on its fourth generation 3D printer, the MakerBot Replicator 2.

The company has also come out with a 3D scanner, called the MakerBot Digitizer, that can scan an object with lasers and record the image on a camera. The scanned image is then transposed into a file that can be uploaded to the printers to re-create the object. While not always a precise copy -- a 3D printed replica can be off in size by as much as 2 millimeters - a scanner can be used to create multiple, functional objects.

Bre Pettis, who co-founded MakerBot in 2009, was on hand at the store opening to cut a ceremonial ribbon and wax poetic about a 3D printer industry today that he says is not unlike that of the personal computer industry in the early 1980s.

In 1981, Pettis said his parents purchased their first computer, an Apple II. It was a pivotal event in his life, Pettis said.

"I can really credit the fact that my folks as early adopters and got me into computers when I was nine as being one of those things that got me here today - having access to technology," Pettis said.

Bre Pettis, co-founder of MakerBot, stands behind the fourth generation of his company's desktop 3D printer at the opening of a Boston retail store

Pettis created his first 3D printer because he was enamored with the technology, but he couldn't afford his own.

"They were like a hundred thousand to millions of dollars to get one. We didn't know any better, so we decided to try it out and make one," he said.

Together with Adam Mayer, and Zach "Hoeken" Smith, Pettis built the first MakerBot, which came as a bunch of components that had to be assembled by the user.

Today, MakerBot Replicator 2 3D printers come fully assembled and have a starting price of $2,199.

Pettis has also started a crowdsourcing campaign to create a fund that will allow schools to get their own 3D printers.

The initiative, a partnership between MakerBot, America Makes, and Autodesk, began on Nov. 12 and allows people to pledge money to DonorsChoose.org, a crowdfunding site just for teachers. Teachers can then register on DonorsChoose.org for a MakerBot printer.

Lucas Mearian covers storage, disaster recovery and business continuity, financial services infrastructure and health care IT for Computerworld. Follow Lucas on Twitter at @lucasmearian, or subscribe to Lucas's RSS feed . His email address is lmearian@computerworld.com.