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AIR UNIVERSITY

AIR COMMAND AND STAFF COLLEGE

How Small Is Too Small?

Technology into 2035

Paul E. Kladitis

Major, USAF

Air Command and Staff College

Wright Flyer Paper No. 46

Air University Press

Air Force Research Institute

Maxwell Air Force Base, Alabama

December 2010
ii

This Wright Flyer Paper and others in the series are 

available electronically at the Air University Research 

Information Management website at http://research

.maxwell.af.mil and the AU Press website at http://

aupress.au.af.mil.

Disclaimer

Opinions, conclusions, and recommendations expressed or implied within are 

solely those of the author and do not necessarily represent the views of Air University, the United States Air Force, the Department of Defense, or any other US 

government agency. Cleared for public release: distribution unlimited.
iii

Foreword

It is with great pride that Air Command and Staff College 

presents another in a series of award-winning student research projects from our academic programs that reach 

nearly 11,000 students each year. As our series title indicates, we seek to promote the sort of imaginative, forwardlooking thinking that inspired the earliest aviation pioneers, 

and we aim for publication projects which combine these 

characteristics with the sort of clear presentation that permits even the most technical topics to be readily understood. We sincerely hope what follows will stimulate thinking, invite debate, and further encourage today’s air war 

fighters in their continuing search for new and better ways 

to perform their missions—now and in the future.

ANTHONY J. ROCK

Brigadier General, USAF

Commandant

v

Abstract

The Department of Defense (DOD) anticipates the realization of biomimetic bird and two-inch, insect-sized systems 

within the 2015–47 period. Although robot systems of one 

millimeter or smaller are not explicitly specified in current 

DOD and Air Force technology road maps, the technological 

aims towards this size can be clearly inferred from official 

documents. This research assesses the likelihood of, and 

barriers to, the realization of true microrobots and nanorobots (defined as submillimeter-sized robots of micro-meter 

and nanometer proportions, respectively) that can perform 

in military applications by 2035. This research finds that 

the realization of true microrobots for military applications 

by 2035 is unlikely, except for a single case of microrobots. 

Furthermore, the realization of true nanorobots for military applications by 2035 is even more unlikely. Technological advancements accrued through striving towards the 

goals of true microrobots and nanorobots are critical if the 

United States is to achieve a technological edge in more 

realizable-sized miniature robots for military application. 

Additionally, these technological advancements are critical 

for reducing the size and payload of other military systems, 

including satellites, aircraft, weapons, C4ISR (C4ISR concept 

of command, control, communications, computers, intelligence, surveillance, and reconnaissance), and portable sensors. Thus, regardless of the feasibility of submillimetersized robots by 2035, the United States still should 

sponsor research and development of both true microrobots 

and nanorobots.

vii

Acknowledgments

I received some assistance from two special individuals. 

Joseph Mait, who works at the Army Research Laboratory, 

sent his paper on his department’s efforts in small robots. 

From the Air Force Research Laboratory, Dr. Leslie S. Perkins 

sent her briefing regarding her group’s microbiomimetic 

remotely piloted aircraft road map.

1

Introduction

23 JAN 2035, 0032Z—An imperceptible speck 

pierces the thick air and enters the adversary’s 

war room located somewhere on the other side of 

the planet. In his dimly lit control room in the high 

desert of Nevada, Captain Bright cringes slightly 

as he pilots his lead system across the war room. 

“It’s still unnerving to me,” he remarks to his pal at 

the next terminal. “I’m two freakin’ feet in front of 

the defense minister’s face, and he can’t even see 

me!” Bright perches his microrobot onto the defense 

minister’s left epaulet and repositions it until the 

adversary’s entire campaign plan is in full view. Imagery and audio data stream in for the J-2.

After two weeks of assessing the situation, adversary analysts finally determine that all of the command and control computers in the bunker malfunctioned from the same cause sometime between 

0300 and 0320. It appears that the VCC [positive 

supply voltage] pins on each microprocessor chip 

were severed. It was as if small explosions occurred at each pin location.

The preceding fiction may soon become fact.

Problem Background and Significance

Current trends in Department of Defense (DOD) research, development, and acquisition of remotely piloted 

systems point towards an evolution in remotely piloted or 

autonomous vehicles to systems the size of insects or much 

smaller.1 Both the DOD and the United States Air Force 

(USAF) technology road maps anticipate demonstration 

and operation of bird- and insect-sized systems capable of 

persistent intelligence, surveillance, and reconnaissance 

(ISR) and limited kinetic attack abilities by roughly 2015–47.2

Specifically, the Air Force Research Laboratory (AFRL) goals 

are to demonstrate bird-sized systems by 2015 and insectsized systems by 2030.3 The AFRL’s goals are to demon-
2

strate robust palm-sized air- and ground-based systems by 

roughly 2018.4

The DOD presently uses micro to refer to small autonomous systems about the size of one to two feet, or bird 

sized.5 The DOD uses nano to refer to small autonomous 

systems the size of a large insect (i.e., about two inches).6

However, these systems should more appropriately be labeled 

miniature systems or robots. This paper deals with the concepts of true microrobot and nanorobot use for military applications. True means the robots embrace micrometer and 

nanometer proportions, respectively. Hence, a microrobot 

is herein defined as a robot of about one by 10-6 meters (one 

micrometer, one micron, or 1 μm) or a robot constructed 

from components of micron proportions. Therefore, a microrobot could range in size from 1 μm to a few millimeters 

(mm). However, this report limits future microrobot projections to no greater than 1 mm. The diameter of a human 

hair is approximately 100 μm, and the diameter of a human 

red blood cell is 7 μm. From the perspective of a macroworld observer, a land, aerial, or aquatic microrobot would 

appear at its largest as an ant, gnat, or plankton, respectively, and at its smallest, it would be invisible. A nanorobot 

is defined as a robot of about one by 10-9 meters (one nanometer or 1 nm) or a robot constructed from components of 

nanometer proportions. Therefore, a nanorobot could range 

in size from 1 nm to a few microns in length. The spacing 

between crystalline silicon atoms is 0.543 nm, and molecules are of nanometer size. From the perspective of a macroworld observer, a nanorobot would be invisible.

Although systems 1 mm or smaller are not explicitly 

specified in current DOD and USAF technology road maps, 

the technological aims towards this size are clearly implied. 

Additionally, even though this report focuses on true microrobots of less than 1 mm in size, some of the results of this 

research can be extended to the larger insect-sized microrobots because they will have to overcome some of the same 

technology barriers to be realized.

This report analyzes and assesses the likelihood that 

true microrobots and nanorobots that can perform in military applications will be developed by 2035. This report also 

identifies key technological barriers to that development. 

Additionally, it argues that the DOD should still sponsor 
3

research and development (R&D) of both microrobots and 

nanorobots, even if their realization by 2035 is unlikely. 

This sponsorship provides a critical catalyst for driving 

both the miniaturization and the integration of sensors, 

communication systems, propulsion systems, munitions, 

control systems, power supplies, and packaging for use in realizing larger insect-sized systems and other military systems.

Background on Current DOD

Miniature Robots

Table 1 summarizes current DOD miniature robot characteristics. The USAF currently employs the Battlefield Air 

Targeting Micro Air Vehicle (BATMAV [also known as Wasp 

III]), a flying robot used for situational awareness and reconnaissance in special operations.7 The Marine Corps and 

the US Navy also utilize the Wasp III.8 Several hundred such 

vehicles currently reside in the DOD inventory.

System Domain Control Propulsion Payload Size & 

Weight Endurance

BATMAV

(Wasp III)

air,

50–500 

feet 

operating 

altitude,

10k feet 

max 

altitude

autonomous or 

remote

fixed wing, 

propeller, 

battery 

powered

GPS/inertial 

navigation 

system 

navigation, 

autopilot, two 

high-resolution 

video cameras 

(front/side look), 

infrared (IR), 

L-band (1–2 

Gigahertz) data 

link

12×16 in., 

1 lb.

40 mph, 45 

minutes

Tactical 

MiniUnmanned 

Air Vehicle

same as 

above 

w/11k ft. 

max 

altitude

same as 

above

same as 

above

same as above 

except no IR

20×21 in., 

1 lb.

50 mph, 25 

minutes

Toughbot ground remote wheeled, 

battery 

powered

two video 

cameras, audio 

sensor

6×8 in., 

2.1 lb.

2 hours

Throwbot ground remote same as 

above

one video 

camera

6×2.5 in., 

12 oz.

2 hours

Table1. Summary of current DOD miniature robot system characteristics

Source: Created by the author

The Army currently employs the Tactical Mini Unmanned 

Air Vehicle (TACMAV), which is similar to the BATMAV.9 The 
4

Army and the Marine Corps presently employ the “Toughbot,” 

and they are developing the “Throwbot,”10 wheeled ground 

robots used for clearing buildings and short-range reconnaissance. Fifty-one Toughbots are already fielded.

In the 2015–47 period, the DOD anticipates the demonstration of biomimetic miniature robots. Biomimetic implies 

the mimicking of movement and appearance of such biological organisms as birds or insects with flapping wings or 

as crawling ground creatures. Biomimetic operation enables 

more covert operations by allowing the robot to better blend 

into the expected natural environment.

The realization of the novel size of the miniature robots 

has been enabled by advances in microscale technologies 

mostly from the fields of microelectronics, microelectromechanical systems (MEMS), and materials science over 

the past 30 years. Additionally, insect-sized miniature robots 

suitable for military application should be achievable in the 

near future.

Background on Current Microrobots

Credible scientific research in microrobot and microrobotenabling technology has been conducted since the late 1980s11

(including early 1990s Defense Advanced Research Project 

Agency–sponsored research). To date, crude microbots and 

microrobot components intended for crawling, flying, and 

swimming have been demonstrated for potential use in closequarters inspection and medical and micro-/nano-nanometer 

manipulation/assembly applications.12 Most of the current 

microrobot systems range in size from one centimeter to a 

few millimeters in length, demonstrate only crude movement under pristine laboratory conditions, and lack any 

integrated electronic control circuitry, onboard power supplies, sensors, or communication systems. Figure 1 shows 

scanning electron micrograph and captured video images of 

a microrobot fabricated on a 4.5-mm-square-by-0.5-mmthick silicon chip.13 The microrobot demonstrated linear 

motion at 453 μm/minute using 96 polycrystalline silicon 

thermal actuator legs arranged in six groups that mimicked 

the motion of six-legged insects. The microrobot was externally 

powered through three thick tethered gold bond wires 25 μm 

thick with an electric power consumption of 0.9 watts (W). 
5

Figure 2 shows a captured video image of a microrobot 15 

mm long fabricated out of a silicon chip.14 This microrobot 

demonstrated linear motion of several mm/minute using 

eight silicon-heated polymide joint actuator legs. The micro-robot was externally powered through three tethered 

gold bond wires 25 μm thick with an electric power consumption of 1.3 W.

Figure 1. Scanning electron micrographs and video image of a 4.5×4.5×0.5 

mm microrobot. (Reproduced from Paul E. Kladitis and Victor M. Bright, 

“Prototype Microrobots for Micro-Positioning and Micro-Unmanned Vehicles,” 

Sensors & Actuators A: Physical 80, no. 2 [2000]: 132–37.)

Figure 2. Captured video image and graphical depiction of a microrobot 15-

mm long. (Reproduced by permission from Thorbjorn Ebefors et al., “A Robust Micro Conveyer Realized by Arrayed Polyimide Joint Actuators,” Journal 

of Micromechanics and Microengineering 10, no. 3 [2000]: 337–49.)
6

A more integrated microrobot is that of Hollar et al., consisting of an integrated actuator foot, control circuitry, and 

solar cell. It should be able to demonstrate crude, uncontrolled linear movement about a few microns/minute with 

an electrical power consumption of 2.6 μW.15 This microrobot 

is 8.6 mm in length. Figure 3 shows a captured video image 

of this integrated and autonomous microrobot.

As shown in figure 4, the most advanced integrated and 

autonomous microrobot to date is the I-Swarm microrobot.16 The I-Swarm microrobot is approximately 4 mm by 

4 mm by 3 mm tall and consists of integrated solar cells 

used for power, light tracking, and reprogramming communication; an IR unit used for sensing and communicating 

with other I-Swarm microrobots; an application-specific integrated circuit used for overall control; three piezoelectric 

legs used for forward, reverse, and z-axis rotation movements; a piezoelectric touch sensor; and power storage 

Figure 3. Captured video image of an integrated and autonomous microrobot. (Reproduced from Seth Hollar et al., “Robot Leg Motion in a PlanarizedSOI, 2 Poly Process,” Proceedings of the Solid-State Sensor, Actuator, and 

Microsystems Workshop [Hilton Head Island, SC, 2–6 June 2002], 54–58.); 

and, reproduced by permission from S. Hollar et al, “Solar Powered 10 mg 

Silicon Robot,” MEMS 2003, Kyoto, Japan, 19-23 January 2003.
7

capacitors. The I-Swarm components are integrated through 

a flexible printed circuit board. Locomotion is limited to operation on a flat sheet of 8.27×11.69-inch paper illuminated 

by a high-intensity lamp and an overhead image projection 

system used for programming the microrobots and displaying graphical navigation cues for the microrobots to follow.

Figure 4. Captured video image of an I-Swarm microrobot. (Reproduced by 

permission from R. A. Casanova et al., “Integration of the Control Electronics 

for an mm3

-Sized Autonomous Microrobot into a Single Chip,” Proceedings of 

the 2009 IEEE International Conference on Robotics and Automation [Kobe, 

Japan, May 2009], 121–27.)

 *ASIC: application-specific integrated circuit.

In summary, the state of the art of microrobots is limited 

to sizes greater than 1 mm in length and to limited sensing 

and crawling operations in highly controlled laboratory environments. No integrated flying microrobots, at the scales 

discussed in this section, have been demonstrated. The 

micron scale of microrobot components has remained the 

same since their inception 30 years ago. What has advanced 

is the growing body of knowledge of microrobot construction 

and motion schemes, novel integration techniques, and microelectronics capabilities. It may take another 30 years of revolutionary breakthroughs to reach submillimeter-sized microrobots with robust autonomy, sensing abilities, and propulsion 

systems in real-world operational environments.

(C) 2009 IEEE
8

Background on Nanorobots

Nanorobotics is an emerging research field and can be 

generally divided into two areas: nanometer-scale manipulation of nanometer-sized objects and construction of 

nanometer-scale robots.17 The first area, nanometer-scale 

manipulation, is already showing tangible results such as 

the manipulation of nanometer-sized particles using an 

atomic-force microscope tip or the manipulation of individual atoms using the electron beam of a scanning tunneling microscope.18

The second area, nanometer-scale robots, is only theoretical. Presently, the primary goal for nanorobots is that of 

an assembler, a self-replicating machine used to assemble 

materials or objects from the bottom up.19 Most research in 

this area focuses on computer-aided modeling of such biological components as deoxyribonucleic acid (DNA) or proteins in hopes of someday harnessing their natural functions 

to perform nanoscale tasks. For example, Miki Hirabayashi 

and others propose using synthetically programmed DNA 

strands to realize various specific self-assembled DNA structures that can perform such specific tasks at the nanometer 

scale as communicating with bacteria.20

Nanorobots that have practical military application, like 

those proposed by K. Eric Drexler as “universal assemblers” 

with the ability to reorder atoms “with the precision of programmed machines,” have not yet been demonstrated in 

any respect.21 The most likely contribution in the near future 

of the larger field of nanotechnology will be the realization 

of nanoscale components (i.e., sensors, control circuitry, 

and power sources) used to help realize submillimeterscale microrobots.

Future Concept of Operations

There presently exists no coherent work outlining concepts of operation (CONOPS) for using microrobots or nanorobots in military applications.22 One notable contribution 

to microrobot CONOPS comes from a 1995 chief of staff of 

the Air Force–directed study of future capabilities required 

to ensure air and space dominance.23 The study was per-
9

formed by Air University through the Air Force Institute of 

Technology. Excerpts from the study follow:

“Attack microbots” describes a class of highly miniaturized (one millimeter scale) electromechanical systems capable of being deployed 

en masse and performing individual or collective target attack. Various deployment approaches are possible, including dispersal as an 

aerosol, transportation by a larger platform, and full flying/crawling 

autonomy. Attack is accomplished by a variety of robotic effectors, 

electromagnetic measures, or energetic materials. Some “sensor microbot” capabilities are required for target acquisition and analysis. A 

“swarm” of 1 mm scale, flight-capable MEM(S) platforms provides 

unobtrusive, pervasive intervention into adversary environments 

and systems. Extremely small size provides high penetration capabilities and natural stealth.

“Sensor microbots” describes a class of highly miniaturized (millimetersized) electromechanical air and ground systems capable of being 

deployed en masse to collect data, perform individual and collective 

data fusion, and communicate that data for further processing and 

distribution. Various deployment approaches are possible, including dispersal as an aerosol, transportation by a larger platform, and 

full-flying/crawling autonomy. Data collection is accomplished 

through miniaturized onboard sensors, typically restricted to one or 

two sensors per unit due to size and power limitations. Communications are possible by transmission through relay stations “relaybots” 

or physical collection of the microbots. Some applications of sensor 

microbots are security net to guard own assets, surveillance and 

reconnaissance, and intelligence gathering on adversary assets.24

Overall, the CONOPS presented below follow directly 

from a military interpretation of the aforementioned commercial microrobot applications of close-quarters inspection, medical, manipulation, and assembly discussed 

above. Additionally, concepts for microrobot CONOPS can 

be derived from miniature robot roles defined in the DOD 

Unmanned Systems Integrated Road Map and the United 

States Air Force Unmanned Aircraft Systems Flight Plan. 

These defined miniature robot roles are battlefield situational awareness, indoor or outdoor reconnaissance, surveillance, target recognition, sensing, lethal attack, irregular 

warfare, cyber attack, and swarming.25 In essence, military 

microrobots will require capabilities similar to today’s 

Global Hawks and Predators. The overall CONOPS will be 

presented in terms of a surface- or land-based mission scenario (microrobot and nanorobot operation in space and 

underwater domains is assumed to be impractical). Larger 

robots are assumed more suitable for space and under-
10

water domains (e.g., space mines, directed energy offensive 

satellites, submarine remoras, etc.).

This report offers two novel sets of four futures scenarios 

CONOPS for microrobots and nanorobots, respectively. As 

shown in figure 5, independent implies each individual robot contains all the component functions necessary to conduct a mission alone, whereas distributed implies different 

component functions will be distributed among several robots to conduct a mission. Remotely piloted implies the robot will be remotely controlled during the entire mission, 

whereas autonomous implies the robot will perform independently, with possible limited remote control direction, throughout the mission. Each quadrant will dictate plausible robot 

technology requirements.

2 1

System Function

3 4

System Control

Distributed Independent

Autonomous Remotely Piloted

Figure 5. Four-quadrant futures scenarios CONOPSs for microrobots and 

nanorobots. (Created by the author)
11

Ingress of Quadrant 1 Robots: Independent and

Remotely Piloted

Microrobots will be delivered (airdropped or ground released) to the general target area by a larger host such as a 

manned/remotely piloted vehicle, a kinetic projectile, or a 

human host.26 Because of their small mass, microrobots 

will be highly survivable during such high accelerations 

and decelerations as those experienced by a tank or artillery 

shell. For example, such high-performance munitions as 

the 105-mm and the 120-mm armor-piercing, fin-stabilized 

discarding sabot (i.e., a device used in a firearm or cannon 

to fire a projectile) produce very high in-bore accelerations 

of 60,000 Gs, where 1 G is the acceleration due to gravity. 

Theoretical predictions for silicon microscale objects suggest survivability up to 136,000 Gs.27 For microrobots to 

traverse relatively large distances to the general target area 

on their own will be as plausible and practical as that of 

such submillimeter biological organisms as gnats or fleas to 

perform the same feat. Therefore, it is unlikely microrobots 

will be able to traverse large distances to the general target 

area in a timely and reliable manner on their own. For microrobots relatively large distances will be defined by the endurance of their propulsion system and will be assumed in 

this CONOPS as any distance over a mile, with the exception of the ability to make course corrections during a highaltitude airdrop. Travel modes of crawling or swimming are 

assumed impractical and are discussed later in detail.

Once released from the host platform, an internal safe 

and arm mechanism will activate the microrobot. Depending on the mode of communication, the microrobots will be 

controlled from the host-delivery platform or some other 

nearby control or relay platform. Under remote control, the 

microrobots will fly to their final targets through caves, 

ducts, or cracks. During ingress to the final target, some of 

the microrobots may be positioned to set up a radio frequency 

(RF) or optical communication relay chain to communicate 

with the outside world. The establishment of a communication relay chain will be dependent on the magnitude of isolation of the final target operating area.

The number of microrobots the host platform delivers 

will depend on the specific mission and will include enough 
12

to establish a communication relay chain and perform the 

specific mission with redundancy. Controllers will have to 

use a remote control system suitable for maintaining control of several microrobots. Quadrant 1 microrobots will require some form of cooperative artificial intelligence to aid 

in the coordinated control of several microrobots. Nanorobots 

will not operate in this quadrant because of the expected 

limitations of their abilities due to their extremely small size.

Ingress of Quadrant 2 Robots: Independent

and Autonomous

Ingress procedures for Quadrant 2 microrobots will be 

identical to Quadrant 1 microrobots except that they will fly 

to their final targets through caves, ducts, or cracks using 

a combination of predefined waypoints, target coordinates, 

and artificial intelligence. Just as moths home in on light 

and mosquitoes home in on heat, the artificial intelligence 

of microrobots will home in on various multispectral signatures while maneuvering around obstacles. Multispectral 

signatures would include electronic emissions, chemicals 

(e.g., biological or synthetic such as DNA, scents, explosives, 

fuels, etc.), sounds, light, images, or heat. The artificial intelligence of Quadrant 2 microrobots will also have to handle 

some form of cooperative behavior to aid in the coordinated 

movement of several microrobots.

Quadrant 2 microrobots may not require a communication relay chain during ingress unless their mission requires the transmission of data to or from an isolated operating area. Therefore, fewer microrobots may be delivered. 

Nanorobots will not operate in this quadrant because of the 

expected limitations of their abilities due to their extremely 

small size.

Ingress of Quadrant 3 Robots: Distributed and

Autonomous

Ingress procedures for Quadrant 3 microrobots will be 

identical to those of Quadrant 2 microrobots. Depending on 

the specific mission, the number of microrobots will include 

enough to establish a communication relay chain (if required) and enough to perform the specific mission with 

distributed function and with redundancy.
13

Nanorobots will have Quadrant 3 capability. Due to their 

extremely small size, each nanorobot will possess only a 

singular capability; therefore, they are classified as distributed in function. Similarly, because of their nature and 

small size, they will not be remote controllable; nonetheless, they are also classified as autonomous in control. 

Quadrant 3 nanorobots will not have target homing and obstacle navigation abilities like Quadrants 2 and 3 microrobots. Nanorobots will have to be delivered precisely to 

their target by a larger host such as a microrobot, a larger 

manned/remotely piloted vehicle, or a human host.

Ingress of Quadrant 4 Robots: Distributed and

Remotely Piloted

Ingress procedures for Quadrant 4 microrobots will be 

identical to Quadrant 1 microrobots. Depending on the 

specific mission, the number of microrobots will include 

enough to establish a communication relay chain and 

enough to perform the specific mission with distributed 

function with redundancy. Nanorobots will not operate in 

this quadrant because of the expected limitations of their 

abilities due to their extremely small size.

Mission of Quadrant 1 Robots: Independent and

Remotely Piloted

Once microrobots reach their targets (e.g., open areas of 

enemy activity, command posts, offices, hideouts, computer/

weaponry circuit boards, antennas, satellites, desks, and 

light fixtures perched atop an enemy soldier’s hat or body 

part, etc.), they will be used to gather various multispectral 

(electronic signals, sound, images, chemical signatures, 

etc.) intelligence; reconnoiter; release individual or collective explosive charges, poisons, or corrosives; reprogram 

equipment; or sabotage with plausible deniability. Gathered 

data will not be stored for later retrieval but will be transmitted back to the control station in real or near-real time.

Microrobots will hover, reconnoiter, or find traverse stationary objects using their flying propulsion system. Motion 

such as crawling will be performed through small incremental movements using their flying propulsion system. 

Nanorobots will not operate in this quadrant because of the 
14

expected limitations of their abilities due to their extremely 

small size.

Mission of Quadrant 2 Robots: Independent and

Autonomous

The mission of Quadrant 2 microrobots will be the same 

as that of Quadrant 1 microbots. An additional mission for 

Quadrant 2 microrobots may include passive monitoring. 

In this case, a propulsion system will not be necessary. 

These microrobots will be delivered during egress and will 

passively monitor the target area from wherever they have 

landed. Nanorobots will not operate in this quadrant because of the expected limitations of their abilities due to 

their extremely small size.

Mission of Quadrant 3 Robots: Distributed 

and Autonomous

The mission of Quadrant 3 microrobots will be the same as 

that of Quadrant 1 microrobots with the exception of distributed operation: one microrobot captures images; another, audio; a third, signals intelligence (SIGINT); and a fourth, kinetic 

effects. Alternatively, the collection of a single type of information may be distributed. For example, if the video resolution of 

a single microrobot is not sufficient to capture meaningful images alone, several microrobots may work to form a synchronized composite image similar in function to an insect’s compound eye. Additionally, Quadrant 3 microrobots may also 

perform a propulsionless passive monitoring mission similar 

to that of Quadrant 2 microrobots.

Due to the nature of a nanorobot, the mission of Quadrant 3 nanorobots will probably be like a synthetic “virus” 

targeted against enemy materiel and, possibly, personnel. 

In essence, the mission of Quadrant 3 nanorobots will be a 

targeted chemical reaction. For example, nanorobots will 

render such enemy materiel as explosives and computer 

processors inert, reprogrammed, or reengineered.
15

Mission of Quadrant 4 Robots: Distributed and

Remotely Piloted

The mission of Quadrant 4 microrobots will be the same 

as that of Quadrant 1 microrobots with the exception of 

distributed operation. Nanorobots will not operate in this 

quadrant because of the expected limitations of their abilities due to their extremely small size.

Egress

The egress procedures for all quadrant microrobots and 

nanorobots are the same. Microrobots and nanorobots will 

be considered expendable and will remain at the target area 

at the end of the mission. Reverse engineering or exploitation of a microrobot would be difficult but not impossible. 

An enemy analyst could observe the exterior construction 

of a microrobot using a high-powered optical microscope or 

scanning electron microscope. Furthermore, nondestructive inspection of the microrobot will be nearly impossible 

due to the packaging technique of the microrobot. However, 

an analyst could use a focused ion beam to cut the microrobot and then observe interior cross sections of the microrobot using transmission electron microscopy. Ultimately, 

if exploitation of a microrobot were a concern, the microrobot 

could self-destruct or dissolve via a dual-use reactive packaging medium. Due to the extremely small size of nanorobots, the collection and exploitation of nanorobots will 

be impractical.

Countermeasures 

To counter microrobots and nanorobots, an adversary 

must deny their presence and their ability to communicate. 

A detection capability is impractical. Because of the robot’s 

invisibility due to its small size, if an adversary were to try 

to monitor the electromagnetic spectrum for microrobot 

communication, the adversary would not know whether the 

detected signals were from some distant source or a robot. 

Ultimately, an adversary would have to resort to some 

broadband low-power jamming on-site to deny microrobots’ 

ability to communicate. Jamming may be undesirable if it 

interferes with the adversary’s own operations. Line-of-
16

sight optical communication by microrobots would be 

nearly impossible to detect and deny. To deny the presence 

of microrobots about 1 mm or smaller, an adversary must 

operate in a clean-room or semiclean-room environment 

that utilizes carefully sealed enclosures with air duct filtration 

capable of blocking particles smaller than 1 mm in diameter. 

At a minimum, an adversary may have to construct enclosures meeting *US FED STD 209E **Class 100 or ***ISO 4 

standards that statistically block particles greater than 5 μm 

in diameter. Ultimately, most adversaries may deem countermeasures against microrobots logistically impractical.

Logistics and Disposal

Microrobots and nanorobots will be mass produced and 

constructed as single expendable items. They will be stored 

in mission-tailored dispenser cartridges ready for loading 

on a host delivery platform. The robot-loaded mission dispenser cartridges will be stored in the clean and dry manner of conventional ammunition to prevent premature fouling or corrosion. The only maintenance required will be 

premission interrogation to confirm data links and microrobot system readiness. If an unacceptable number of 

microrobots failed, the dispenser cartridge will be discarded. Depending on the microrobot power source, microrobot sensor chemistry, and nanorobot composition, microrobots and nanorobots will have limited shelf lives. 

Unused microrobots and nanorobots will be incinerated.

*US FED STD 209E: Federal Standard 209E, “Airborne Particulate 

Cleanliness Classes in Cleanrooms and Clean Zones,” General 

Services Administration, 11 September 1992.

**Class 100: Describes air with not more than 100 particles per 

cubic foot (of air). The particles are 0.5 microns and larger, and no 

particles are microns or larger.

***ISO 4: Describes air with not more than 83 particles per 

cubic meter (of air). The particles are one micron and larger, and 

no particles are five microns or larger.
17

Ethics

The public may perceive microrobots and nanorobots as 

chemical or biological weapons, especially if these weapons 

are used against personnel, and thereby consider them to 

violate certain principles of jus in bello. 

However, microrobots are distinctly different from chemical 

or biological agents. Even though a microrobot could enter 

a human’s body through the mouth, nose, or ears, a microbot is no more dangerous than if a human were to swallow 

a bullet or a radio. Nanorobots, however, will be constructed 

from a combination of natural or synthesized biological and 

chemical components. Depending on their specific mission, 

nanorobots may differ from chemical or biological agents only 

by their designed function; thus, legally, nanorobots may 

be classifiable as chemical or biological agents. A key consideration of the legal classification of microrobots and nanorobots may hinge on whether they are used against personnel.

Microrobot System Components

Figure 6 illustrates a relevance tree for the microrobots 

discussed in the CONOPS. To establish a maximum sizelimit baseline for the required microrobot components, this 

Figure 6. Graphical illustration of a microrobot relevance tree. (Created by 

the author)
18

For each quadrant capability, table 2 lists the allocated 

quantity units (Qty.) for each component, the additional control electronics (Add. CE) required for each component, and 

the allocated volume (Vol.) for each component. The control 

Table 2. Tabular microrobot relevance tree including allocated 

component volumes

Quadrant 1

(Ind/RP)

Quadrant 2

(Ind/Aut)

Quadrant 3

(Dis/Aut)

Quadrant 4

(Dis/RP)

Component Qty. Add.

CE

Vol.

(mm3

)

Qty. Add.

CE

Vol.

(mm3)

Qty. Add.

CE

Vol.

(mm3)

Qty. Add.

CE

Vol.

(mm3)

Control 

Electronics*

5.35 0.259 5.35 0.259 4.9 0.258 4.9 0.258

Nuclear 

Sensor 

Elements

0.3 0.15 0.015 0.3 0.15 0.015 0.3 0.15 0.016 0.3 0.15 0.016

Biological 

Sensor 

Elements

0.3 0.15 0.015 0.3 0.15 0.015 – – – – – –

Chemical 

Sensor 

Elements

0.3 0.15 0.015 0.3 0.15 0.015 – – – – – –

Optional TRX 2 1 0.097 2 1 0.097 2 1 0.105 2 1 0.105

Acoustic 

Sensor

0.3 0.15 0.015 0.3 0.15 0.015 – – – – – –

RF TRX 

Elements

1 1 0.048 1 1 0.048 1 1 0.053 1 1 0.053

Timing 

Elements

1 0.25 0.048 1 0.25 0.048 1 0.25 0.053 1 0.25 0.053

Navigation 

System

1 1 0.048 1 1 0.048 1 1 0.053 1 1 0.053

Propulsion 

Elements

4 0.25 0.193 4 0.25 0.193 4 0.25 0.211 4 0.25 0.211

Munitions† – 0 – – 0 – – 0 – – 0 –

Power 

Elements

1 0.25 0.048 1 0.25 0.048 1 0.25 1 0.25 0.053

Integration 

Overhead 

(20%)

0.200 0.200 0.200 0.200

Totals 16.6 4.35 1.000 16.6 4.35 1.000 15.2 3.9 1.000 15.2 3.9 1.000

Source: Created by the author.

Legend: Qty. (quantity), Vol. (volume), RF (radio frequency), TRX (transceiver), Ind. (independent), 

RP (remotely piloted), Aut. (autonomous), Dis. (distributed), Add. CE (additional control electronics 

required for each component). 

*Quantity equals one central control processor plus the total of the “Add. CE” column. 

†Munitions are part of the microrobot packing material accounted for in integration overhead.

report makes several assumptions about the size and number 

of components required to construct a microrobot suitable 

for military applications. First, a fabricated microrobot will 

probably not have a cube shape; however, for size estimation 

purposes, this report assumes a microrobot of one cubic 

millimeter (mm3). Table 2 represents a tabular version of the 

relevance tree for each quadrant microrobot and includes 

allocated component quantities and volumes.
19

electronics row reserves one control processor for a central 

control function plus the total of the additional control electronics column. The allocated volume for each component is 

calculated by dividing 1 mm3 by the total number of allocated 

components in the Qty. column and then multiplying this by 

the allocated quantity unit for each component. 

In estimating the allocated volume for each component, 

this report makes several subjective assumptions concerning the respective sizes of each component. For example, 

nuclear, biological, chemical, or acoustic sensor elements 

are allocated approximately one-third (0.3) the space of a 

navigation system component. Also, the additional control 

electronics allocations are subjective estimates. Furthermore, the absence of allocations for biological, chemical, or 

acoustic sensor elements in the Quadrants 3 and 4 columns is not intended to imply microrobots will not have 

these capabilities. Since Quadrants 3 and 4 microrobots 

have distributed function, they will have only a single sensing capability. This single sensing capability is symbolically 

allocated in the “Nuclear Sensor Elements” row.

Table 3 represents a relevance tree for a special case of a 

Quadrant 3 microrobot. This special-case Quadrant 3 microrobot is a passive, propulsionless robot that simply relays 

sensed information from wherever it is placed or lands. This 

special case represents a streamlined microrobot with the 

minimum number of components to accomplish a plausible, 

passive mission as described in the CONOPS. This microrobot 

may require either an optical or an RF communication system 

to relay sensed information (volume allocation is represented 

in “RF TRX Elements”), timing elements to synchronize data, 

a navigation system to geolocate data, and munitions as part 

of the integration overhead for self-destruction.

The primary significance of tables 2 and 3 is that the allocated component volume values will be used later to estimate 

the maximum component sizes required to realize 1 mm3

microrobots by 2035. For example, a single control electronics 

processor unit or a power supply will have to fit in a volume of 

0.048 mm3 for Quadrants 1 or 2 microrobots, 0.053 mm3 for 

Quadrants 3 or 4 microrobots, or 0.094 mm3 for special-case 

Quadrant 3 microrobots to realize a microrobot of total volume 

1 mm.3 Equivalently, 5.35 control electronics processor units 

will have to fit in a volume of 0.259 mm3 for Quadrants 1 or 2 
20

Nanorobot System Description

The nanorobots will be constructed from synthesized or 

naturally occurring molecular biological components. They 

must be able to replicate or move in or beside the object 

where they are placed as they process their target material 

Maximum Component 

Volume (mm3)

Cube Length max 

volume1/3 (mm)

Quadrants 1 & 2 0.048 0.363

Quadrants 3 & 4 0.053 0.376

Quadrant 3 Special Case 0.094 0.455

Table 4. Maximum microrobot component volumes

Source: Created by the author

Component Qty. Add.

CE

Vol.

(mm3)

Control Electronics* 3.5 0.329

Sensor Elements 1 0 0.094

Optical TRX Systems 0 0 0.000

RF TRX Elements 1 1 0.094

Timing Elements 1 0.25 0.094

Navigation System 1 1 0.094

Propulsion Elements 0 0 0.000

Munitions† - 0 -

Power Elements 1 0.25 0.094

Integration Overhead 

(20%)

0.200

TOTAL 8.5 2.5 1.000

Table 3. Special case, passive and propulsionless, Quadrant 3 microrobot relevance tree showing required number of components and 

volume allocation for each component

Source: Created by the author

Legend: Qty. (quantity), Vol. (volume), RF (radio frequency), TRX (transceiver), Add. CE (additional control electronics required for each component).

 *Quantity equals one central control processor plus the total of the “Add. CE” column.

 †Munitions are part of the microrobot packing material accounted for in integration overhead.

microrobots. For simplicity this report assumes a maximum 

size limit for any single microrobot component of one whole 

volume unit. Table 4 summarizes these maximum component 

volume units.
21

and either physically or chemically rearrange the molecules 

or atoms of the target material. The nanorobots will neither 

communicate nor collect data. They will simply react with 

their target material until their process has culminated or 

until their reaction has become limited.

Overcoming Technical Barriers

Control Electronics

State-of-the-art microprocessor electronic circuits are currently fabricated on crystalline silicon chips approximately 1 

centimeter (cm) by 1 cm by 0.5 mm thick (thumbnail in size). 

The primary factor that determines the required size of electronic circuits and support systems, given a fixed transistor 

size and technology, is processing speed. Processing speed can 

be increased either by increasing the clock speed or by using 

parallel processing. Increasing the clock speed allows faster 

processing speed on a single chip or circuit, but it also requires 

more electrical power (e.g., 143 W for a high-performance processing unit with a heat sink), which in turn is dissipated in the 

form of heat. The heat is usually removed by a system of heat 

sinks and forced convection fans. However, the heat removal 

system can consume considerably more space than the microelectronic circuitry. Parallel processing is achieved by using redundant microelectronic circuits that break the processing 

down into several parallel tasks. In this manner, a microelectronic circuit can process information quickly, even with a 

slower clock speed, because the processing task is being performed in parallel. The drawback in terms of size for this 

method is the requirement for more chip surface area for the 

additional parallel processing circuitry.

Lower power-consuming microelectronic circuits are realized by decreasing the clock speed and reducing the power 

supply voltage. The reduction of power supply voltage is 

driven by several factors, especially reduction of transistor 

power consumption, reduced transistor channel length, 

and reliability of gate dielectrics. Current portable low-cost, 

hand-held, and uncooled battery-operated circuits presently consume approximately 3 W per 1 cm2 chip.
22

Figure 7 provides a plot of projected electronics chip size. 

The curve in figure 7 extrapolates that in 2035, a 0.486-mmby-0.486-mm electronics chip will hold the same number of 

transistors, with overhead, as a 1 cm2 chip does today. This 

should indeed be plausible, since the 2035 chip size corresponds to a transistor (including overhead) density of 233,582 

million transistors per cm2, whereas the atomic surface density 

of crystalline silicon is 678,313,306 atoms per cm2. Based on 

the microrobot maximum component volumes listed in table 4, 

this chip will meet Quadrants 1 and 2 volume restrictions as 

long as the substrate thickness is no greater than 0.048 mm3 ÷ 

(0.486 mm x 0.486 mm) = 0.203 mm. Figure 8 shows the 

extrapolated power requirement for the 2035 chip of 0.007 W 

or 7 megawatts (mW). This power requirement will be used later 

in this section to estimate required microrobot power supply 

capacity.

Figure 7. Plot of projected high-volume microprocessor chip size. (Constructed from data 

from International Technology Roadmap for Semiconductors, “The International Technology Roadmap for Semiconductors: 2009,” 75, Table ORTC-2C. See the predicted 

number of transistors [including the logic core, memory, and interconnection overhead] 

per approximately 1 cm2 high-volume microprocessor chip for the period 2009 to 2024. 

Data from 2025 to 2035 was extrapolated by curve fitting a fourth-order polynomial to the 

2009 through 2024 data and extrapolating to 2035. The curve extra polates that in 2035, 

a 0.486-mm-by-0.486-mm electronics chip will hold the same number of transistors, with 

overhead, as a 1 cm2 chip does today.)

*CMOS: complementary metal oxide semiconductor.
23

At some point, transistor technology will have to transit 

away from the current complementary metal oxide semiconductor (CMOS) technology to reach the target chip size 

by 2024 and, consequently, by 2035. Potential replacement 

technologies include carbon-based nanoelectronics, spinbased devices, ferromagnetic logic, atomic switches, and 

nanoelectromechanical system (NEMS) switches. Additionally, 

although the projected microprocessor size is on track to 

meet a single microrobot maximum component volume, the 

multiple microprocessor chips required to run a complete 

microrobot will have to be stacked together in some fashion 

to fit inside a microrobot. This will require a three-dimensional 

(3-D) integration technique yet to be realized.

In summary, current commercial electronics trends are on 

track to yield electronics suitable for incorporation into microrobots by 2035. However, the DOD may have to drive the transition from CMOS technology to keep pace with the current 

Figure 8. Plot of high-volume microprocessor chip power requirements corresponding to the decreasing chip sizes in figure 7. The curve shows that the 

extrapolated power requirement for the 2035 chip is 0.007 W or 7 mW. This 

plot was constructed from the data in figure 7 and assumes a target power 

consumption of 3 W, per low-power 1 cm2

 chip, is held as a design constant 

from 2009 to 2035. (Created by the author)
24

trend should the commercial sector choose not to. Additionally, 

the DOD may have to drive R&D in reliable 3-D circuit-stacking 

integration. This agrees with the National Research Council 

(NRC) Committee on Implications of Emerging Micro- and 

Nanotechnologies assessment that next-generation electronic 

devices such as scaled CMOS, single-electron transistors, spinbased electronics, molecular electronics, and carbon nanotube 

electronics may be available for application sometime within 

the next 10–40 years.28

Nuclear, Biological, and Chemical Sensors

Current commercial nuclear, biological, and chemical 

sensors are field-effect transistor or diode junction based.29

Additionally, NEMS sensors based on resonating thin films 

and nanowires and optical-based nanoparticle systems are 

currently being developed.30 The individual sensor element 

sizes, especially for transistor-based sensors, are already 

well under the microrobot maximum component volumes 

listed in table 4. Presently, these sensors are normally fabricated on relatively large substrates too large for microrobots. The only technical challenge for the future is in integrating these sensors on smaller substrates that will meet 

the microrobot maximum component volumes. This integration should be achievable by 2035. It agrees with the 

NRC’s assessment that MEMS—or nanotechnology-based 

chemical and biological sensors—may be available for application sometime within the next 10 years.31

Multispectral Optical Components and Transceiver

Elements

Current charge-coupled display (CCD) 640-by-480-pixel 

(0.5 megapixel) chips are approximately 2 mm by 2 mm by 

0.5 mm thick. Complete digital microcamera systems including optical components, at present, are rarely smaller 

than 5 mm3.

32 Decreasing the size of imaging systems may 

require such new paradigms as compound eye systems 

found in small biological organisms. These could be realized 

through microlenses and microlens arrays currently under 

development.33 Additionally, the complete imaging system 

can be further miniaturized using other MEMS-based optical 
25

components with advanced packaging techniques also under 

development.34 

Future microrobots may require high-resolution imaging 

to accomplish their mission. One way to realize this is to 

decrease the imaging pixel size. State-of-the-art imaging 

pixel sizes can range from 10 μm by 10 μm to 4 μm by 4 

μm.35 However, reducing the size of imaging pixels and associated optical components may encounter physical barriers 

due to the diffraction of light, since the visible light wavelengths range from 0.38 to 0.72 μm, and IR wavelengths of 

interest can range up to several hundred micrometers. If 

the microrobots were to operate in a distributed sense to 

achieve higher-resolution imaging where each robot represents a few pixels, the current absence of suitable miniaturized high-precision position and timing subsystems for 

composite image correlation and construction presents a 

technology barrier to microrobot-distributed imaging.

Adding the requirements of night vision, IR imaging, and 

transceivers for line-of-sight intramicrorobot communications further complicates the situation. Night vision requires miniaturized light amplification components. Highperformance IR imaging requires miniaturized pixel-cooling 

subsystems unless a suitable miniaturized uncooled IR imaging system is realized by 2035. Optical components for 

millimeter-sized intramicrorobot communications have recently been developed. The I-SWARM microrobot uses a spatially arranged surface-emitting, light-emitting diode and 

photodetector line-of-sight, microrobot intracommunication 

subsystem that measures 3 mm by 3 mm by 1 mm thick.36

In summary, current state-of-the-art imaging systems do 

not meet microrobot maximum component volumes. Fortunately, R&D is headed in the right direction. Current commercial trends are driving the miniaturization of imaging 

systems for handheld devices and medical instruments. Furthermore, since imaging technology is closely related to standard integrated circuit technology, it may follow standard 

integrated circuit miniaturization trends to 2035. However, 

the DOD may have to drive R&D to reach submillimetersized high-resolution imaging systems, night-vision components, and uncooled IR imaging systems. Furthermore, the 

DOD may have to drive R&D of non-CCD/CMOS-based imaging pixels for both visual and uncooled IR imaging.
26

Acoustic Sensors

An example of a state-of-the-art microsized acoustic sensor 

is fabricated from piezoelectric thin films and measures 

600 μm by 600 μm by 2.2 μm thick with a total volume of 

0.0008 mm3.

37 Since the size of this device is much less 

than microrobot maximum component volume requirements (0.048 mm3), this device should be on track to complement microrobot systems by 2035. Reduction in thinfilm width dimensions (under 600 μm), to be able to 

physically incorporate this into a microrobot while remaining sensitive to the 20 hertz–20 kilohertz audio range, could 

pose a technical challenge. However, this challenge can 

most likely be overcome by reducing the thickness of the 

sensing film appropriately. The primary technical challenge 

for the future is in integrating this sensor on substrates or 

with microelectronics that will meet the microrobot maximum component volumes. This possibility should also be 

achievable by 2035. It agrees with the NRC’s assessment 

that MEMS- or nanotechnology-based multispectral sensors may be available for application sometime within the 

next decade.38

Multispectral RF Components and Transceiver

Elements

Communication for remote control or intelligence and reconnaissance data telemetry via current RF system paradigms may be impractical due to physical barriers at this 

small scale regarding antenna efficiency, monolithic microwave integrated circuit (MMIC) size, and lack of transmission power to reach the outside world. For example, for efficient transmission, a dipole antenna should span a 

quarter of the respective RF communication wavelength. 

We can assume that a quarter wavelength antenna of 1 mm 

requires an RF communication frequency of 75 gigahertz 

(GHz) that is in the US industry standard W-band, international standard extremely high frequency band, or military 

standard M-band.39 Development of W-band MMIC components and design techniques is currently under way. In 

terms of power requirements, assuming 0 dBi (decibel isotropic) gain microrobot transmit-and-receive antennas, 75 

GHz, and a very good receive sensitivity of -120 dBm (decibel 
27

milliwatt) (very slow data transmission rate), microrobots 

could theoretically communicate at a distance of 2,500 feet 

(ft.) with 7 mW of available transmission power (same power 

estimated for a single integrated circuit processor chip in 

2035), 1,000 ft. with 1 mW, and 30 ft. with 1 microwatt

(μW).40 Alternatively, assuming a higher data transmission 

rate with a receiver sensitivity of -80 dBm, microrobots could 

theoretically communicate at a distance of 30 ft. with 7 mW, 

10 ft. with 1 mW, and four inches with 1 μW of available transmission power. Current state-of-the-art broadband SIGINT 

systems, including RF processing, amplifier, and filter components, are about one meter in size. It is highly unlikely 

that such a system can be reduced in size to meet microrobot 

maximum component volumes by 2035.

In summary, it is unlikely, given size and power constraints, that robust RF communication and sensing systems will be available by 2035 for practical microrobots 

without major technological breakthroughs. This evaluation roughly agrees with the NRC’s assessment that certain 

MEMS-based RF sensor components may be available for 

application sometime within the next 10–40 years.41 Furthermore, it is unclear whether MMIC technology will follow 

standard integrated circuit miniaturization trends to meet 

microrobot component-size constraints by 2035. One recent discovery using carbon nanotube resonators holds 

promise.42 Nanotube resonators, a completely new paradigm in RF system design, may enable further miniaturization; however, adequate transmission power to communicate with the outside world still may be an issue, since this 

procedure seems to be independent of RF system technology. 

Finally, another recent discovery that may be used to overcome size and transmission power barriers is communication using quantum entanglement.43

Precision Timing

Miniaturization of rubidium- and cesium-based atomic 

clocks is currently an aggressive area of research.44 Miniaturized atomic clock systems are about 1 cm in size and 

consume approximately 75–360 mW of power.45 The current R&D paradigm consists of the direct miniaturization of 

large-scale atomic clocks based on the absorptive properties 
28

of rubidium and cesium vapor. The greatest technical challenge in atomic clock miniaturization is the miniaturization 

and packaging of the absorption cell (the “physics package”). 

It is unclear whether atomic clocks based on this paradigm 

can be further miniaturized to meet microrobot maximum 

component volumes by 2035. The DOD should drive R&D 

into further miniaturizing atomic clocks by two orders of 

magnitude more or find alternative paradigms in precision 

timekeeping.

Navigation Components

Current miniaturized inertial navigation systems are 

based on MEMS inertial elements, including accelerometers and gyroscopes. Inertial element grades are classified 

into three categories of increasing performance: tactical, 

navigation, and military. With few exceptions, most MEMS 

inertial components are tactical grade at best. However, 

tactical grade components may be suitable for the microrobot mission. For example, some of today’s miniature military aerial systems and munitions take advantage of the 

Honeywell HG1930 MEMS inertial measurement unit, 

which is roughly two inches in diameter and 1.3 inches in 

height and which consumes less than 3W of power.46 MEMS 

accelerometers and gyroscopes are electrostatically actuated resonating masses usually fabricated from silicon and 

are about the size of a few hundred micrometers in width 

and a few micrometers in thickness. Although each device 

is relatively small, the combination of three accelerometers, three gyroscopes, reference devices, control electronics, and other supporting components required to realize true navigation can become sizeable. Inertial element 

performance is a function of the mass of the element. The 

smaller the inertial element, the less sensitive it becomes. 

Therefore, a physical barrier exists to the further decrease 

in size of these elements.

In summary R&D is headed in the right direction in trying to miniaturize navigation systems. However, given the 

physical inertial barrier combined with the current size of 

MEMS-based navigation systems, it is unlikely that navigation systems based on the current MEMS paradigm can be 

further miniaturized to meet microrobot maximum compo-
29

nent volumes by 2035. The DOD should drive R&D into 

further miniaturizing navigation systems based on alternative paradigms.

Propulsion

Even if all the aforementioned microrobot internal component technical barriers could be overcome by 2035, nature itself presents a significant exterior obstacle. The state 

of the art in microrobot propulsion is based on crawling, 

and this development will be impractical for several reasons, 

including the fractal lengthening of a surface’s topology at 

the submillimeter scale, which could result in a never-ending 

journey through canyon-like crevices and around mazes of 

boulder-like particulates. Crawling microrobots could be 

knocked off-center by particulates or become entrapped in 

a quagmire of dust. A flying propulsion system will have to 

be powerful enough to enable the microrobot to withstand 

breezes, strong air currents, dust, and rain. The propulsion 

system will also have to be powerful enough to break the 

microrobot free from the surface tension of moist surfaces, 

small films of liquids, and the attraction of charged surfaces or environmental particulates. The propulsion system 

will have to reach relatively high velocities for the microrobot 

to travel to the target in a timely manner and achieve 

enough momentum to penetrate the aforementioned environmental conditions.

The DOD projects that the miniature, insect-sized “NanoFlapping Air Reconnaissance Vehicle” will achieve technology 

readiness level (TRL) 6 by fiscal year 2013 with a less-thantwo-inch wingspan and a maximum weight of 10 grams.47

Theoretically, a 1-mm wingspan can provide enough lift to 

propel true microrobots.48 However, it remains unclear 

whether actual microflight can be achieved in practice or 

whether it will be an effective form of propulsion for microrobots employed in a military mission. Most likely, a currently unknown method of propulsion may have to be discovered for true microrobots to surpass nature for military 

applications. One possible wingless method of flight propulsion may be found in acoustic streaming jets.49 Additionally, due to the extremely small masses at the microscale, 

microscale objects effectively operate in microgravity condi-
30

tions similar to operation in space. Therefore, another possible method of microflight propulsion could be one that 

takes advantage of the earth’s magnetic field.50

In summary 30 years have transpired since the inception 

of the microrobot and microrobot propulsion components. 

To date only crude crawling and swimming of millimeterscale robots in highly controlled laboratory environments 

have been demonstrated. Based on this trend, it may be 

another 30 years before robust microflight is realized. This 

assumption agrees with the NRC’s assessment that MEMSbased propulsion may be available for application sometime within the next 10–40 years.51

Micromunitions

For microrobots to deliver appreciable kinetic effects to a 

target, new explosive materials must be found that pack a bigger punch into a smaller package. A possible material candidate currently under investigation includes nanoporous silicon that is reported to have more than doubled the energy 

output of Trinitrotoluene.

52 Other examples include metastable 

intermolecular composites, sol gels, and functionalized carbon nanotubes.53 It is unknown whether materials like these 

will provide enough energy for microrobot mission accomplishment. Another possible munition could be a microsized 

nuclear weapon.

In summary and to the author’s knowledge, no dedicated 

investigation into realizing microscopic explosive charges 

for application with microrobots currently exists. Additional 

research should further define microrobot target sets, associated required kinetic effects, and suitable energetic materials. It is unknown whether an effective explosive-laden 

microrobot is a feasible concept or will be available by 2035.

Power Supplies

Arguably, the most challenging area of miniaturization is 

in the ability to provide a long-endurance power supply for 

autonomous microrobots. Microrobots have been demonstrated to be powered or actuated using tethered wires, 

close-proximity inductive coupling of large coils, closeproximity capacitive coupling, vibration tables, thin-film 

batteries, close-coupled magnetic fields, pulsed laser 
31

beams, or solar power—all impractical for microrobot longdistance, autonomous operations.54 Potential microrobot 

power supply schemes can be divided into two categories: 

self-contained or environment scavenging.

Examples of self-contained power supplies currently under 

development include fuel cells, turbine-powered electrostatic generation, and thin-film batteries that are all still 

too large or for some reason unable to provide enough sustainable energy for microrobots. One promising technology 

for self-contained long-term power generation is alpha- and 

beta-source radioactive decay, or nuclear batteries.55 Another 

technology is a hybrid microscale MEMS fuel cell thin-film 

lithium (Li) ion source.56

An example will demonstrate the current inadequacy of 

self-contained power supplies for microrobots. First, consider 

a quadrant 1 or 2 microrobot that must provide power to 

the following major subsystems: control electronics, optical, 

RF, timing, navigation, and propulsion, altogether representing 14.35 components requiring power (table 2). Second, 

assume each of the 14.35 components requires the same 

power as a single microprocessor chip of 7 mW, for a total 

of approximately 100 mW of power required (14.35 x 7 mW 

= 100 mW). Third, assume the microrobot was powered by a 

thin-film Li ion battery that fits into the maximum microrobot component volume size of 0.048 mm3 from table 4. Assuming a thin-film Li ion energy density of 200 watt-hour/

kilogram (Whr/kg) and a Li compound density of 8 x 10-7

kg/mm3, the battery can provide 7.68 x 10-6 Whr of power 

(200 Whr/kg x 8 x 10-7 kg/mm3 x 0.048 mm3 = 7.68 x 10-6

Whr). Therefore, the battery would be able to power the microrobot while all systems are functioning for 7.68 x 10-6

Whr / 0.1 W = 7.68 x 10-5 hours, or 0.3 seconds.

Examples of environment-scavenging power supplies 

currently under development include electromagnetic inductive coupling, electrostatic capacitive coupling, piezoelectric vibration, thermoelectric, pulsed laser, and photovoltaic.57 Another example was demonstrated with silicone 

elastomer polydimethylsiloxane cantilever legs with rat 

cardiomyocyte heart cells cultured on their surfaces.58

These microrobot legs demonstrated movement for up to 

two weeks while immersed in physiological liquids. These 

power source methods could provide indefinite power as 
32

long as they can be scaled down to fit within a microrobot 

and the microrobot can remain in the presence of the respective external stimuli or condition. Remaining within 

the external stimuli would prove impractical based on the 

microrobot CONOPS defined in this report.

In summary R&D is headed in the right direction in its 

search for long-endurance miniaturized power supplies. 

The DOD projects that “opportunistic power-grazing” technology for larger robot systems will achieve TRL 6 by 2031.59

However, no suitable power supply for robust autonomous 

microrobots exists at present. Unless a significant technological breakthrough occurs soon, suitable power supplies 

for microrobots are unlikely by 2035. This timeline agrees 

with the NRC’s assessment that MEMS-based power 

sources may be available for application sometime within 

the next 10–40 years.60

Integration: Assembly, Interconnection, and Packaging

For complete and robust microrobot systems to be realized, they need to be suitably mass-assembled from all of the 

aforementioned subsystems. One-by-one machine-assisted 

assembly will be impractical due to the large quantities of 

microrobots required. During microrobot fabrication, all microrobot components will have to be assembled into their proper 

relative positions, electrically or optically interconnected 

with each other, and suitably sealed together (packaged) to 

protect the internal components from environmental contamination, while at the same time providing suitable external 

interfaces for the optical transceivers, biological sensors, 

chemical sensors, acoustic sensors, and propulsion elements.

Most likely, due to their small size, microrobots will not 

be assembled using current machine-automated massmanufacturing paradigms. One feasible mass-manufacturing 

technique is to fabricate thousands of copies of complete 

microrobot systems on a single substrate, deposit and pattern a final protective thin-film coating over each robot, and 

subdivide the substrate into individual robots. Currently, 

however, the aforementioned microrobot subsystems are 

fabricated using disparate technologies and materials. This 

condition will most likely persist into the near future. Therefore, any plausible manufacturing technique must accom-
33

modate the assembly of individual subsystems fabricated 

from disparate technologies. R&D has been poised for this 

inevitability, as evidenced in the investigation of micro 

and nano self-assembly techniques, which include the 

self-arrangement or positioning of microscale components 

by harnessing the surface tension of liquids, forces of magnetic and electric fields, adhesion of functionalized surfaces, strategically positioned microactuators, vibration, 

fluid-flow forces, centrifugal forces, shrinkage of polymers, 

and geometric matching.61

Assuming machine-automated micromanipulation technology will not be able to assemble complex 3-D arrangements and make intrasubsystem electrical connections required by the microrobots postulated herein, the following 

self-assembly paradigm is proposed. This paradigm assumes the microrobot-packaging medium will be engineered to facilitate three functions: assembly, interconnection, and weaponization. First, each individual microrobot 

component must incorporate the following additional design features: (1) chemically functionalized edges and/or 

surfaces, (2) an assembly facilitating geometry, (3) a packaging medium-phobic surface for those component surfaces that must face the exterior of the microrobot, and (4) 

self-routing electrical interconnection pads. Second, all required components for an individual microrobot will be injected into a droplet of the packaging medium. Once in the 

packaging medium droplet, the components will orient 

themselves with respect to each other via the attractive 

forces of the functionalized edges and surfaces, the repulsive forces of the packaging medium-phobic surfaces, and 

their assembly-facilitating geometries. Third, upon an external stimulus, the self-routing interconnection pads will 

form electrical pathways to their matching interconnect 

pads amongst the other components. The formation of the 

electrical pathways is facilitated by the packaging medium 

chemistry and is analogous to the growth of a biological 

nervous system. Ultimately, the packaging medium will 

cure, providing a hard encasing for the microrobot. The assembled microrobot will also be spheroidal in shape due to 

the surface tension of the liquid packaging medium before 

curing. The packaging medium will also serve as the explosive material for self-destruction or the delivery of kinetic 
34

effects. In the case that self-routing interconnects are not 

feasible, the self-routing interconnection pads could be replaced by tuned optical communication transceivers. In 

this case, the packaging medium must be engineered to 

provide total internal optical reflection so that the tuned 

optical transceivers on one component can communicate 

with matched sets on other components regardless of location. Additionally, in this case interconnections with the 

power supply must somehow be hard connected.

In summary current microassembly techniques are not 

able to assemble, interconnect, and package microrobots 

as postulated herein. It is unknown if this ability will be 

realized by 2035. The NRC’s assessment is that some suitable assembly and packaging technologies may be available 

for application sometime within the next 10–40 years.62

Nanorobot Feasibility Evaluation

With respect to nanorobots, the same technical challenges that will plague microrobots will be magnified by 

several orders of magnitude. Additionally, due to physics at 

this scale, remote communication and information storage 

may be impossible.63 Nanorobots will have to be employed 

exclusively and autonomously. Even if nanorobots were realizable, they will not be able to process their target material because the energy required to break and make atomic 

bonds will render atomic rearrangement unfeasible.64

Furthermore, even if the atomic rearrangement function 

were realized, the time required for nanoscale objects to 

complete the macroscale sabotaging transformation of 

enemy materials would be impractical.65 For these and a 

host of other practical physical limitations, the realization of nanorobots as postulated in this report may be 

unlikely regardless of period.

Summary and Conclusions

The current state of miniature DOD robots is represented 

by vehicles about a foot in size containing video and audio 

reconnaissance capability that can fly or roll on the ground 

with wheels. Additionally, the DOD goal is to realize biomimetic bird and two-inch, insect-sized systems within the 
35

2015–47 period. The current state of complete microrobot 

systems is represented by robots about a half of a centimeter 

in size with crude crawling and limited serial optical communication capability in highly controlled laboratory environments. Furthermore, nanorobots are not close to being 

demonstrated. Table 5 summarizes feasibility assessments, 

and table 6 assesses the availability of microrobots and 

nanorobots by 2035.

Microrobot

Subsystem

Current 

R&D 

Vector

R&D

Driven 

Commercially?

DOD 

Focused 

R&D

 Required?

Available

 by

 2035?

Technology 

Breakthrough 

Required?

Control 

Electronics

Appropriate Yes Maybe Likely Yes

Nuclear Sensors Appropriate Yes Maybe Likely No

Biological 

Sensors

Appropriate Yes Maybe Likely No

Chemical 

Sensors

Appropriate Yes Maybe Likely No

Optical Systems Appropriate Yes Yes Possible Yes

Acoustic Sensors Appropriate Yes No Likely No

RF Systems Appropriate Yes Yes Unlikely Yes

Precision Timing Appropriate Yes Yes Unlikely Yes

Navigation 

Systems

Appropriate Yes Yes Unlikely Yes

Propulsion Appropriate Maybe Yes Unlikely Yes

Munitions Needs focus No Yes Unlikely Yes

Power Supply Appropriate Yes Yes Unlikely Yes

Integration Appropriate Yes Yes Unlikely Yes

Table 5. Summary of microrobot subsystem analysis and assessment

Source: Created by the author

Table 6. Assessment of the availability of microrobots and nanorobots 

by 2035

Robot System Available by 2035?

Quadrant 1 Microrobots Unlikely

Quadrant 2 Microrobots Unlikely

Quadrant 3 Microrobots Unlikely

Quadrant 4 Microrobots Unlikely

Special Case Quadrant 3 Microrobots Possible

Nanorobots Unlikely

Source: Created by the author
36

Cutting-edge research is currently under way in miniaturized components and technologies required to construct 

true microrobots. However, key technical challenges and 

barriers exist in the further miniaturization of electronics, 

optical systems, RF systems, precision timing, navigation 

systems, propulsion, munitions, power supplies, and component integration, making realization of true microrobots 

by 2035 unlikely. Prospects for overcoming these challenges include next-generation electronic components, 

nanoresonator-based RF systems and sensors, quantum 

entanglement communication, acoustic streaming propulsion systems, nuclear or environment-scavenging power 

sources, self-routing nervous-system-like interconnects, 

and novel packaging/self-assembly mediums. One possible 

exception is the realization of special-case Quadrant 3 

microrobots, passive propulsionless robots that simply relay sensed information from wherever they are placed or 

land. Special-case quadrant 3 microrobots are similar in 

concept to “smart dust” research that has been under way 

for the past several years.66 The realization of nanorobots 

for military applications may be unlikely regardless of period. 

In fact, such present-day information operations core capabilities as electronic warfare and computer network operations are more practical for accomplishing the military missions envisioned for nanorobots.67

If technical challenges are not overcome, larger insectsized robots may be the only practical choice for realization 

by 2035. However, technological advancements accrued by 

striving towards the goals of true micro and nanorobots are 

critical if the United States wishes to achieve a technological 

edge in more realizable-sized miniature robots for military 

application. Additionally, these technological advancements are critical for reducing the size and payload of a 

host of other military systems, including satellites; aircraft; 

weapons; command, control, communications, and computers ISR; and portable sensors. Thus, regardless of the 

feasibility of submillimeter-sized robots by 2035, the United 

States should continue to sponsor R&D of both true microrobots and nanorobots.
37

Notes

(All notes appear in shortened form. For full details, see the appropriate 

entry in the bibliography.)

1. Secretary of Defense, Integrated Road Map; and Secretary of the Air 

Force, Flight Plan, 2009–2047.

2. Secretary of Defense, Integrated Road Map, 165; and Secretary of 

the Air Force, Flight Plan, 2009–2047, 35.

3. Air Force Research Laboratory (AFRL), “Micro Air Vehicles,” 1; and 

AFRL, Science and Technology Strategy, 22.

4. Mait, “Army Research Laboratory’s Program,” 3; and Mait, telephone 

interview by the author, 26 January 2010.

5. Secretary of the Air Force, Flight Plan, 2009–2047, 35; and Niles and 

Tran, “Study of Autonomous Micro-Robots,” 1–22.

6. Secretary of the Air Force, Flight Plan, 2009–2047, 35.

7. Secretary of Defense, Integrated Road Map, 54.

8. Ibid., 81.

9. Ibid., 79.

10. Ibid., 132–33.

11. Trimmer, “Microrobots and Micromechanical Systems,” 267–87. 

12. Yeh, Kruglick, and Pister, “Microelectromechanical Components,” 

346–49; Ebefors et al., “Robust Micro Conveyer,” 337–49; Shimoyama et al., 

“Simple Microflight Mechanism,” 148–52; Fukada et al., “Micro Mobile 

Robot,” 204–10; Gad-el-Hak, MEMS Handbook, 28-1–28-42; and Fatikow 

and Rembold, Microsystem Technology and Microrobotics, 303–65.

13. Kladitis and Bright, “Prototype Microrobots,” 132–37.

14. Ebefors et al., “Robust Micro Conveyer Realized by Arrayed 

Polyimide Joint Actuators,” 337–49.

15. Hollar et al., “Robot Leg Motion,” 54–58.

16. Casanova et al., “Integration of the Control Electronics,” 3007–12.

17. Weir, Sierra, and Jones, “Review of Research in the Field of 

Nanorobotics,” 8.

18. Ibid., 15–29.

19. Hall, Nanofuture, 122.

20. Hirabayashi et al., “Toward Self-Assembly,” 530–35.

21. Drexler, Engines of Creation, 14.

22. In the public domain and to this author’s knowledge.

23. Jackson, Jones, and Lehmkuhl, “Operational Analysis,” xii.

24. Ibid., 113, 128.

25. Secretary of Defense, Integrated Road Map, 17; and Secretary of 

the Air Force, Flight Plan, 2009–2047, 25, 34–35.

26. Solem, “Application of Microrobotics,” 1.

27. Kladitis, “Materials for Harsh Environments.” 

28. National Research Council Committee, Implications, 8.

29. Son and Ziaie, “Implantable Wireless Microdosimeter,” 256–59. 

30. Cobianu et al, “Nano-Scale Resonant Sensors,” 259–62. 

31. Endo, Yanagida, and Hatsuzawa, “Optical Chemical Sensor,” 947–50; 

and National Research Council Committee, Implications, 8.

32. Volkel, Eisner, and Weible, “Miniaturized Imaging Systems,” 461–72.

33. Di, Lin, and Du, “Eyes Imaging System,” 13–18.
38

34. Jung et al., “Miniaturized Camera System,” 819–23.

35. Itakura et al., “IT CCD Image Sensor,” 65–70.

36. Corradi et al., “Optical System,” 1–16.

37. Ren et al., “Micromachined Piezoelectric Acoustic Device,” 1–6.

38. National Research Council Committee, Implications, 8.

39. Calculated from f = c / λ.

40. Calculated using the Friis transmission equation Pr = Pt Gt Gr 

(λ / 4πR)2.

41. National Research Council Committee, Implications, 10.

42. Dragoman and Dragoman, “Tunneling Nanotube Radio,” 1–3.

43. Rosenfeld et al., “Atom-Photon Entanglement,” 1.

44. Wang, Lin, and Guo, “Micromachined Rb-85 Filter,” 911–14.

45. Stern, Stern, and Levy, “Nano-Atomic-Clock,” 1; and Kitching et al., 

“Power Dissipation,” 781–84.

46. Mohr and Fitzpatrick, “Navigation System,” 19–24.

47. Secretary of Defense, Integrated Road Map, 165.

48. Kubo, Shimoyama, and Miura, “Insect-Based Flying Microrobots,” 

386–91; and Bronson et al., “Flapping Wings,” 1047–50.

49. Parviz et al., “Ultrasonic Electrostatic Resonators,” 586–89.

50. Johnson, “Tether Solution,” 38–43.

51. National Research Council Committee, Implications, 10.

52. Currano, Churaman, and Becker, “Nanoporous Silicon,” 2172–75.

53. Miziolek, “Nanoenergetics: An Emerging Technology Area of National 

Importance,” 43–48.

54. Gad-el-Hak, MEMS Handbook, 28–34.

55. Hassan and Faris, “Self-Reciprocating Cantilever,” 2758–62.

56. Chen, Vogt, and Rincón-Mora, “Design Methodology,” 674–77.

57. Chalasani and Conrad, “Energy Harvesting Sources for Embedded 

Systems,” 442–47.

58. Kim et al., “Cardiomyocytes,” 1405–8.

59. Secretary of Defense, Integrated Road Map, 168.

60. National Research Council Committee, Implications, 10.

61. Syms et al., “Self-Assembly of Microstructures,” 387–417; and 

Winkleman et al., “Templated Self-Assembly,” 900–910.

62. National Research Council Committee, Implications, 10.

63. Berube, Nano-Hype, 65–73.

64. Ibid.

65. Ibid.

66. Cook, Lanzisera, and Pister, “SoC Issues,” 117–96.

67. Joint Publication (JP) 3-13, Information Operations, II-4–II-5.
39

Abbreviations

AIT automatic identification technology

ALCM air-launched cruise missile

BCT brigade combat team

BRIC Brazil, Russia, India, and China

CAC common access card

DOD Department of Defense

EPC electronic product code

ERS expeditionary rescue squadron

ETSI European Telecommunications Standard 

Institute

GAO Government Accountability Office

GSEN Global Supply Enterprise Network

HF high frequency

IEC International Electrotechnical Commission

IFF identification, friend or foe

ISO International Organization for Standardization

IT information technology

IUID item unique identification

LF low frequency

MEMS micro-electromechanical system

MICAP mission capable

PICS positive inventory control system

RF radio frequency

RFID radio frequency identification

UHF ultra-high frequency

UID unique item identification

USTRANSCOM United States Transportation Command

VH very high frequency

41

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