Balloon-Assisted Flight of Radio

2304
IEEE TRANSACTIONS ON BIOMEDICAL ENGINEERING, VOL. 56, NO. 9, SEPTEMBER 2009
Balloon-Assisted Flight of Radio-Controlled
Insect Biobots
Alper Bozkurt*, Student Member, IEEE, Robert F. Gilmour, Jr., and Amit Lal, Member, IEEE
Abstract—We report on radio-controlled insect biobots by directing the flight of Manduca sexta through neuromuscular activation. Early metamorphosis insertion technology was used to
implant metal wire probes into the insect brain and thorax tissue.
Inserted probes were adopted by the developing tissue as a result
of the metamorphic growth. A mechanically and electrically reliable interface with the insect tissue was realized with respect to
the insect’s behavioral and anatomical adoption. Helium balloons
were used to increase the payload capacity and flight duration
of the insect biobots enabling a large number of applications. A
super-regenerative receiver with a weight of 650 mg and 750 µW
of power consumption was built to control the insect flight path
through remotely transmitted electrical stimulation pulses. Initiation and cessation of flight, as well as yaw actuation, were obtained
on freely flying balloon-assisted moths through joystick manipulation on a conventional model airplane remote controller.
Index Terms—Biobots, flight control, implantable electrodes, insects, micro-air-vehicles (MAV), radio control, surgery.
Fig. 1.
Life cycle of Manduca sexta with stages of EMIT, as indicated.
I. INTRODUCTION
OR many decades, insect flight has fascinated robotic
engineers confronting challenges in realizing man-made
centimeter-scale flying machines. Insects are self-powered, operate with highly efficient flight muscle actuators, and carry
onboard flight control sensors as well as collision avoidance
systems to perform exquisite acrobatics. Several technical approaches have been explored to develop insect-mimetic smallscale autonomous flying machines [1]. However, it has not been
possible to reach the long mission duration and aerodynamic
performance and maneuverability of insects because the artificial flight actuators are not sufficiently efficient and the power
and energy density of power sources are inadequate for insectlike flight [2].
Another idea has been to directly tame and domesticate the
insect function in a “biobotic” manner by tapping into the insect
F
Manuscript received May 1, 2009. Current version published August 14,
2009. This work was supported by the Defense Advanced Research Projects
Agency (DARPA) Hybrid Insect-Microelectromechanical Systems (HI-MEMS)
Program. Asterisk indicates corresponding author.
A. Bozkurt is with the School of Electrical and Computer Engineering,
Cornell University, Ithaca, NY 14853 USA (e-mail: [email protected]).
R. F. Gilmour, Jr. is with the Department of Biomedical Sciences, Cornell
University, Ithaca, NY 14853 USA (e-mail: [email protected]).
A. Lal is with the School of Electrical and Computer Engineering, Cornell
University, Ithaca, NY 14853 USA (e-mail: [email protected]).
This paper has supplementary downloadable multimedia material available
at http://ieeexplore.ieee.org, provided by the authors. This material includes
a movie [14] in WMV format, which shows neuromuscular actuation results
on balloon-assisted flying insects. The size of the movie is 21.6 MB. Contact
[email protected] for further questions about this work.
Color versions of one or more of the figures in this paper are available online
at http://ieeexplore.ieee.org.
Digital Object Identifier 10.1109/TBME.2009.2022551
nervous system with artificial electronic systems [3]. However,
these methods require delicate microsurgery skills to accurately
place electronics in the insect tissue, where the resultant injury has the potential to affect flight performance. It has also
been challenging to develop permanent and reliable attachment
methods to fix electronic payloads to the insect’s body, which
is covered with weakly attached scales and piles. In order to
solve these issues with adult-stage biobot interfaces, we have
previously demonstrated surgical techniques [early metamorphosis insertion technology (EMIT)] to implant artificial systems into the insect body [4], [5]. In this method, electronic and
mechanical components are introduced into the insect body during early metamorphic stages (Fig. 1), where the metamorphic
growth around the implant provides a strong mechanical attachment, as well as reliable electrical coupling [6]. Moreover, the
surgical procedure is relatively simpler and performed only in
seconds, which potentially enables batch processing and mass
production of such insect biobots. When the adults emerge, these
pupal-stage inserted implants provide a hybrid machine–insect
platform for various biorobotic studies.
The flight control system of moths consists of sensory organs
connected either directly to the brain or to the ganglia distributed
along the body (Fig. 2). Environmental signals received through
these sensors are converted into orderly contractions of muscle
groups after being processed by the ganglia. Various parts of
this system can be stimulated to alter its natural operation in
order to direct the control of flight using external electronics. It
is well established that during natural flight, moths sense various
chemical stimuli through their antennal lobe [7], and maneuver
toward targeted locations such as nectar sources and host plants
0018-9294/$26.00 © 2009 IEEE
Authorized licensed use limited to: UNIVERSIDAD POLITECNICA DE VALENCIA. Downloaded on April 06,2010 at 18:22:37 EDT from IEEE Xplore. Restrictions apply.
IEEE TRANSACTIONS ON BIOMEDICAL ENGINEERING, VOL. 56, NO. 9, SEPTEMBER 2009
2305
Fig. 2. (Left) Points of insertion on the insect anatomy and (right) functional
organization of the insect flight control system.
[8]. They also use their eyes to detect the visual cues to find and
recognize these targets. Insect eyes are part of the exoskeleton
and can only be moved with the head to stabilize the retinal
image of the target. During yaw, for example, the contraction of
the wing muscles is preceded by the rotation of the head toward
the aimed direction. Therefore, the neck muscles are directly
involved in motion directivity [9]. In this study, we have worked
toward stimulating the antennal lobe and the neck muscle of the
hawkmoth Manduca sexta, with an aim of obtaining locomotion
toward the stimulated side to prove the concept of the EMITbased remote-controlled biobotic platforms.
Fig. 3. Pulse shaping at the transmitter and processing on the receiver sides
of the radio system.
II. MATERIALS AND METHODS
The modular remote-controlled insect stimulator platform
consists of three layers: probe, power, and control electronics
(Fig. 4).
A. Design and Fabrication of Stimulation Probe
The control electronics is connected to the neuromuscular
system through the stimulation probe. The probe consists of
biocompatible gold or silver wire electrodes (diameter 200 µm,
A-M Systems, Inc.) soldered to a printed circuit board (PCB)
probe body (FR-4, 4 × 5 mm2 ). The geometry of the electrodes
was designed to target a region spanning the antennal lobe and
the neck muscles [Figs. 2 and 4(c)]. During the EMIT procedure, the wire electrodes are positioned in the pupal tissue
and the PCB is exposed outside [Fig. 5(a)]. After the adult insect emerges, the control electronics is connected to the probe
through a flat flex cable (FFC) connector [Fig. 4(f)]. The copper
traces (200 µm) on the probe body [Fig. 4(d)] match this connector. The manufactured probe weighs approximately 30 mg.
We used silver and gold wires as stimulation electrodes due to
low flexural rigidity, biocompatibility, and lower cost. Although
their stability to electrolytic corrosion is not as good as that
of some other noble metals (such as platinum or iridium) [10],
the softness/flexibility of the wires is required to mechanically
match the forces encountered during the insect-head rotation.
B. Radio and Control Electronics Design
For the transmitter, we use a conventional two-joystick, threechannel, 72 MHz AM transmitter (Futaba, Inc.), which is widely
used for radio-controlled (RC) micro-air-vehicles, model air-
Fig. 4. (a) Description of the balloon-assisted flight setup with the ring inserted
for recording purposes. (b) Details of the assembled system. (c) 3-D bending
of the wire electrodes to target the thorax and antennal lobe. (e) Front side
of the assembled radio board holding the microcontroller and the receiver.
(f) Backside of the board with FFC connectors for (g) battery and (d) probe.
(e) and (f) Magnets taped to the circuit to connect with the balloon.
planes, and helicopters. To receive and demodulate the transmitted pulse position modulation (PPM) stream (Fig. 3), a superregenerative-based receiver architecture was custom built on an
FR-4 PCB [Fig. 4(e)]. This architecture requires fewer electrical
components, and therefore weighs less and consumes minimal
power as a result of self-oscillatory and self-quenching advantages of the “super-regeneration” principle [11]. A microcontroller (PIC12F615) was also connected to the receiver output
to separate the PPM stream into different channels and convert
it into pulsewidth-modulated waveforms to be applied to the
tissue. The position of the transmitter joysticks determines the
frequency and duty cycle of these pulses going to the antennal
Authorized licensed use limited to: UNIVERSIDAD POLITECNICA DE VALENCIA. Downloaded on April 06,2010 at 18:22:37 EDT from IEEE Xplore. Restrictions apply.
2306
IEEE TRANSACTIONS ON BIOMEDICAL ENGINEERING, VOL. 56, NO. 9, SEPTEMBER 2009
for 0 g to ∼5 m for 1 g) and duration (from hours for 0 g to
∼50 s for 1 g) decreases (unpublished observations). This limits
the application space of the aforementioned biobotic platforms.
To overcome this problem, we introduce the concept of balloonassisted insect flight, which reduces the effective weight lifted
by the insect flight [13]. For this purpose, we attached a helium
balloon to the electronics board using two magnets, one glued
to the balloon side and the other to the PCB holding the radio
[Fig. 4(b) and (e)]. The lifting force of the balloon was balanced
with the weight of the insect and the electronic payload. To
record the effect of the actuation in close-up view, we first
introduced an annular ring around the plastic tube between the
balloon and electronics board [Fig. 4(a)]. Then, the annular ring
was removed for free-flight experiments, consisting of takingoff, yawing, and landing by sending pulses from the remote
controller.
III. EXPERIMENTAL RESULTS AND DISCUSSION
Fig. 5. (a) Arrows indicating insertion points of the probe on the pupal stage
and on (b) the emerged adult insect. (c) Probe adoption by the brain tissue
revealed with the removal of the vertex (front part of the head). (d) Location
of the metal wires (lighter color) in the thorax and brain on the reconstructed
X-ray images.
lobe and neck muscles of the insect. The electronics board holding the receiver and microcontroller [Fig. 4(e)] weighs only 70
mg and consumes less than 1 mW of power (∼750 µW static, ∼1
mW dynamic). The line-of-sight transmission distance between
the transmitter and receiver was measured to be approximately
50 m, and the receiver was able to operate more than 5 h with
continuous pulsing. A set of FFC connectors is used to connect the probe and the battery [Fig. 4(f)]. As the power source,
we used an Li–Po battery (3.6 V, 8.5 mAh), which weighs 300
mg [Fig. 4(g)]. This is one of the smallest batteries in terms of
size/energy criterion for a given supply voltage [12]. The overall
system weighs 650 mg.
C. Surgical Insertions
Insects were obtained from the Boyce Thompson Institute
insect growth facility. The probes were surgically inserted into
the insect using the EMIT procedure [6] around seven days
before eclosion [Fig. 5(a)]. The insertion procedure involves
driving the electrode wires through the outer cuticle of the pupae
at the targeted locations. The pupae were anesthetized before the
insertion by being kept at 4 ◦ C for 30 min. After the insertion,
the insects were kept at a dark/light cycled incubator (7 h dark
at 18 ◦ C, and 17 h light at 27 ◦ C) until emergence. During the
development occurring in the incubator, the probes are naturally
secured to the insect body by cuticle healing and tissue growth
around the probes [6].
D. Balloon-Assisted Flight
Manduca sexta can carry up to 1 g of payload. However, as the
payload weight increases, the flight distance (from kilometers
The adult insects emerged from pupae 5–7 days after the surgical insertions [Fig. 5(b)] with an average weight of 2.2 g (only
male adults were used). The successful emergence rate was 84%
(N = 30) and 80% of these adults were able to successfully
inflate their wings. The healed cuticle at the insertion point can
be seen in Fig. 5(b). This healing and the tissue growth around
the inserted probe [Fig. 5(c)] provided a secure attachment of
the payloads to the insect, as a result of which, the EMIT procedure eliminated the need for artificial glues. Typical forces
required to pull the probes out of the insect body were 2 N,
demonstrating the strength of the mechanical coupling to the
tissue. After the emergence, we were able to easily connect the
control electronics and power layers to the probe body through
the FFC connector in 5–10 s without requiring any anesthesia
[Fig. 4(b)].
The helium balloon with 3 L of volume was able to lift
the insect with the added electronics. In addition to increasing the payload capacity, the lift provided by the helium
(1 g/L) helped the insect to conserve the energy used for lifting
its own body weight, thereby potentially increasing the mission
duration. This approach also allows for addition of other electronic components, such as extra power sources for extended
mission duration, sensors for environmental sensing, cameras
for surveillance, and actuators for further detailed control of the
insect flight.
The actuation of the targeted regions with electrical pulses
sent from the transmitter to the antennal lobe caused wing flapping on a resting moth, indicating successful electrical coupling.
A typical dc resistance of the order of 3 MΩ/cm was measured
between the wire electrodes. In the setup with the annular ring,
we were able to initiate natural flight with pulses sent to the
antennal lobe (3.5 Vpp –20 Hz–50% duty cycle). After the flight
was initiated, actuation of the neck muscles with similar pulses
elicited controlled yawing of the insect (∼60◦ /s–80◦ /s). The
flight ceased immediately when the antennal lobe was stimulated
with high-frequency pulses (3.5 Vpp –50 Hz–50% duty cycle).
When the annular ring was removed, we were able to demonstrate a three-task mission of lifting-off, yawing, and landing
Authorized licensed use limited to: UNIVERSIDAD POLITECNICA DE VALENCIA. Downloaded on April 06,2010 at 18:22:37 EDT from IEEE Xplore. Restrictions apply.
IEEE TRANSACTIONS ON BIOMEDICAL ENGINEERING, VOL. 56, NO. 9, SEPTEMBER 2009
2307
assisted flight allows for transport of tens of grams, enabling a
vast number of engineering applications. This work paves the
way for future engineering approaches to understand the insect
flight in more detail and also to facilitate insect-based biobotic
systems as centimeter-scale micro-air-vehicles.
ACKNOWLEDGMENT
The facilities used for this research include the SonicMEMS
Laboratory, the NanoScale Science and Technology Facility
(CNF), and the Nanobiotechnology Center (NBTC) at Cornell
University. The authors would like to thank M. Riccio for technical support and J. Beal for supplying insects.
REFERENCES
Fig. 6. Digitized flight track of the moth as a result of applied stimulation
pulses. The flight control can be best seen in video format [14].
with freely flying insects. A typical trajectory of the insect position obtained during this mission can be seen in Fig. 6. To exhibit
reproducibility, we repeated the same mission three consecutive
times in three different trials. All of these results can be best
seen in movie format [14].1 By feedback-controlled learning of
the yaw motion obtained in various insects, it is plausible to
ascertain the best positions for probe placement and optimized
pulse sequences, a study currently underway.
IV. CONCLUSION
In this study, we demonstrated radio-controlled stimulation of
an insect neuromuscular system to control its flight. The EMIT
process was used to successfully integrate stimulation probes
to the insect tissue. Metamorphic growth after the surgery provided melding metal wires and targeted actuation locations: the
antennal lobe and the neck muscles. Simplicity of the surgical procedure allows for batch processing and mass production
of these hybrid insect–machine systems. Electrical pulsing of
the targeted locations created flight initiation, cessation, and
yaw maneuver on the insects whose flights were supported by
the lifting force of helium balloons. The concept of balloon-
1 Also
[1] C. P. Ellington, “The novel aerodynamics of insect flight: Applications to
micro-air vehicles,” J. Exp. Biol., vol. 202, pp. 3439–3448, 1999.
[2] R. Wootton, “From insects to microvehicles,” Nature, vol. 403, pp. 144–
145, 2000.
[3] C. Diorio and J. Mavoori, “Computer electronics meet animal brains,”
Computer, vol. 36, no. 1, pp. 69–75, Jan. 2003.
[4] A. Paul, A. Bozkurt, J. Ewer, B. Blossey, and A. Lal, “Surgically implanted
micro-platforms in Manduca-sexta,” in Proc. Solid State Sens. Actuator
Workshop, Hilton Head Island, SC, 2006, pp. 209–211.
[5] A. Bozkurt, R. Gilmour, D. Stern, and A. Lal, “Microprobe microsystem
platform inserted during early metamorphosis to actuate insect flight muscle,” in Proc. 21st IEEE Conf. MEMS, Tucson, AZ, 2008, pp. 160–163.
[6] A. Bozkurt, R. Gilmour, A. Sinha, D. Stern, and A. Lal, “Insect machine
interface based neuro cybernetics,” IEEE Trans. Biomed. Eng., to be
published.
[7] P. Kloppenburg, S. M. Camazine, X. J. Sun, P. Randolph, and J. G. Hildebrand, “Organization of the antennal motor system in the sphinx moth
Manduca sexta,” Cell Tissue Res, vol. 287, pp. 425–433, 1997.
[8] M. A. Willis and E. A. Arbas, “Odor-modulated upwind flight of the sphinx
moth, Manduca sexta L.,” J. Comp. Physiol. A, vol. 169, pp. 427–440,
1991.
[9] J. Milde, W. Gronenberg, and N. Strausfeld, “The head–neck system of
the blowfly calliphora: Functional organization and comparisons with the
sphinx moth Manduca sexta,” in The Head–Neck Sensory–Motor System,
A. Berthoz, W. Graf, and P. P. Vidal, Eds. New York: Oxford Univ.
Press, 1992, pp. 64–70.
[10] R. A. Freitas Jr., “Nanomedicine, biocompatibility,” Landes Biosci.,
vol. 2A, pp. 2360–2363, 2003.
[11] D. K. Shaeffer and T. Lee, The Design and Implementation of Low-Power
CMOS Radio Receivers. New York: Springer-Verlag, 1999.
[12] I. Buchmann, Batteries in a Portable World. Overland Park, KS: Ec &
M Books, 1997.
[13] S. Pulla and A. Lal, “Insect powered micro air vehicles,” in Proc. IEEE
ICRA, Kobe, Japan, 2009, to be published.
[14] (2009, Apr. 27). [Online]. Available: http://sonicmems.ece.cornell.edu/
publications/movies/TBME09_2.wmv
available at http://ieeexplore.ieee.org.
Authorized licensed use limited to: UNIVERSIDAD POLITECNICA DE VALENCIA. Downloaded on April 06,2010 at 18:22:37 EDT from IEEE Xplore. Restrictions apply.