Another scenario he suggested the nanodrone could do in the future is fly into a room and drop a poison onto something, such as food, to presumably target a particular individual.

The federal government defines nanotechnology as the science, technology and engineering of things so small they are measured on a nanoscale, or about 1 to 100 nanometers. A single nanometer is about 10 times smaller than the width of a human's DNA molecule.

While nanotechnology has produced major benefits for medicine, electronics and industrial applications, federal research is currently underway that could ultimately produce nanobots.

For one, the Defense Advanced Research Projects Agency, or DARPA, has a program called the Fast Lightweight Autonomy program for the purpose to allow autonomous drones to enter a building and avoid hitting walls or objects. DARPA announced a breakthrough last year after tests in a hangar in Massachusetts.

Previously, the Army Research Laboratory announced it created an advanced drone the size of a fly complete with a set of "tiny robotic legs" — a major achievement since it presumably might be capable of entering a building undetected to perform surveillance, or used for more nefarious actions.

Frightening details about military nanotechnologies were outlined in a 2010 report from the Pentagon's Defense Threat Reduction Agency, including how "transgenic insects could be developed to produce and deliver protein-based biological warfare agents, and be used offensively against targets in a foreign country."

It also forecast "microexplosives" along with "nanobots serving as [bioweapons] delivery systems or as micro-weapons themselves, and inhalable micro-particles to cripple personnel."

In the case of nanoscale robots, Del Monte said they can be the size of a mosquito or smaller and programmed to use toxins to kill or immobilize people; what's more, these autonomous bots ultimately could become self-replicating.

Last month's targeted assassination of Kim Jong-nam, the half-brother of North Korea's ruler, was a stark reminder that toxins are available from a variety of sources and can be unleashed in public locations. It's also been alleged by Russia's Pravda paper that nanoweapons were used by the U.S. against foreign leaders.

A Cambridge University conference on global catastrophic risk found a5 percent risk of nanotech weapons causing human extinction before the year 2100.

As for the mini-nukes, Del Monte expects they represent "the most horrific near-term nanoweapons."

Nanotechnology opens up the possibility to manufacture mini-nuke components so small that they are difficult to screen and detect. Furthermore, the weapon (capable of an explosion equivalent to about 100 tons of TNT) could be compact enough to fit into a pocket or purse and weigh about 5 pounds and destroy large buildings or be combined to do greater damage to an area.

"When we talk about making conventional nuclear weapons, they are difficult to make," he said. "Making a mini-nuke would be difficult but in some respects not as difficult as a full-blown nuclear weapon."

Del Monte explained that the mini-nuke weapon is activated when the nanoscale laser triggers a small thermonuclear fusion bomb using a tritium-deuterium fuel. Their size makes them difficult to screen, detect and also there's "essentially no fallout" associated with them.

Still, while the mini-nukes are powerful in and of themselves, he expects they are unlikely to wipe out humanity. He said a larger concern is the threat of the nanoscale robots, or nanobots because they are "the technological equivalent of biological weapons."

The author said controlling these "smart nanobots" could become an issue since if lost, there could be potentially millions of these deadly nanobots on the loose killing people indiscriminately.

Earlier in his career, Del Monte said he held a secret clearance when he worked on Defense Department programs at Honeywell, ranging from missiles to satellites. He also previously worked on advanced computers at IBM and has several patents on microelectronics. In those roles, he led development of microelectronics and sensors.