Some of the greatest ideas in history have been drawn up on the proverbial "cocktail napkin," and now a pair of student researchers at the University of Alabama, Huntsville, have devised and built a specialized 3D printing extruder which they say will lower the costs of printing cellular structures used in testing drugs.

Calling it the CarmAl extruder, or Carbohydrate Anhydrous Rapid Manufacturing Aluminum extruder, second-year biological sciences students Tanner Carden and Devon Bane have used the device to build a sugar grid which mimics the workings of blood vessels.

The printer system uses software to control a solenoid valve to regulate the timing of nitrogen pushing against a sugar solution. A modular tip and a heating process let the extruder operate at higher temperatures than standard extruders. It's this heating process which allows the device to exact precise control over the viscosity of the sugar solution, and that means more accurate vascular structures can be created as a result.

The work suddenly took flight in earnest when Bane came up with a design on the spur of the moment.

"He thought it up on the spot and he 'freehanded' a drawing of it," Carden says. "He brought me this complex technical drawing – that my dad understood – and the next day my dad handed me this extruder. It's very simple and designed much like a syringe."

Tanner's dad, Rodney Carden, took $12 worth of aluminum and then machined the extruder himself at the General Dynamics plant where he works.

A bit of a science pun, the CarmAl extruder was inspired by 3D printers developed to make specialty candies like caramels.

"We're using the sugar molecules in a form of reverse 3D printing," Carden said. "We first make the structures we want, and then we embed them into a cellular matrix."

The cells are suspended in an "agarose" solution where they propagate the vascular structure before a solvent is used to wash the sugar.

What's left is a cell mass which contains vessels that ape the construction of an actual organ.

Carden says the advantage of the cell mass in testing drugs over flat-dish cell cultures is that the mass accurately resembles living tissues.

According to Carden, the cell mass method prevents necrosis in samples.

Next up for Carden is a trip to the Wake Forest University Institute for Regenerative Medicine for further study of their advanced biological 3D printing techniques. Carden says the sky is the limit for the future of 3D bioprinting.

"At some point, you get to the use of stem cells, and then personalized medicine becomes very affordable," he said.