Leading the charge is Sols Systems, a young startup using 3-D printing to create custom orthotic insoles. It’s not the kind of business investors would call “sexy,” and yet, Sols has attracted plenty of venture interest just a few months into its existence.

Today the company announced it raised $6.4 million in venture funding from Lux Capital, with Founders Fund and existing investors Rothenberg Ventures, Felicis Ventures, FundersGuild, and Grape Arbor VC participating. The company raised a seed round worth $1.75 million in December.

Sols works as such: Foot doctors sign up to use Sols in their offices. Through Sols’ iPad app, they can scan their patients’ feet. Sols then uses 3-D printing to create a mold of the foot and a custom insole for a fraction of the price and time it would normally take.

Since its seed round, Sols has done beta testing with 50 doctors on its platform. (This includes Dr. Ali Sadrieh, the doctor who invented the “Cinderella” procedure, a plastic surgery for women’s feet that makes wearing high heels more comfortable, as recently highlighted in a New York Times article.)

Sols has shipped around 500 insoles while in beta. The cost of custom insoles is up to the doctors, but Sols suggests $500. In 2015, the company will roll out a consumer-facing product, which will offer over-the-counter custom insoles at around $100.

Sols is one of the first companies to emerge using 3-D printing as a basis for a technology platform. Others in the medical field have emerged, including Organovo, a company which prints human organs using live cells, and 3D Systems, which has been rapidly acquiring 3-D printing medical device and prosthetics companies.

Sols co-founder Kegan Schouwenburg has the 3-D printing chops: She was part of the team which helped build out Shapeways’ 25,000-square-foot 3-D printing facility in New York. This year Sols has gone from a small founding team to 12 employees and built out a research and development facility in Manhattan.

Schouwenburg says that, since Sols’ beta launch, she’s been surprised at the demand. “I’ve blown away by what we put on our feet and how far off that is from what our bodies look like,” she says. “It only reinforces the fact that a custom solution is needed. Shoes are not engineered to fit, and it’s something we’ve been okay with for however long.”