This PDF file contains the front matter associated with SPIE Proceedings Volume 8031, including the Title Page, Copyright information, Table of Contents, Introduction (if any), and the Conference Committee listing.
True nanotechnology, defined as the ability to reliably and repeatably fabricate nanostructures with controlled
differences in size, shape, and orientation at precise substrate locations, currently does not exist. There are many
examples demonstrating the capability to grow, deposit, and manipulate nanometer-sized features, but typically these
techniques do not allow for controllable manufacturing of individual structures. To bridge this gap and to unlock the true
potential of nanotechnology for defense sensing applications, the Defense Advanced Research Projects Agency
(DARPA) launched the Tip-Based Nanofabrication (TBN) research program with the intent of achieving controlled
manufacturing of nanostructures using functionalized AFM cantilevers and tips. This work describes the background,
goals, and recent advances achieved during the multi-year TBN program.
Massively parallel scanning-probe based methods have been used to address the challenges of nanometer to millimeter
scale printing for a variety of materials and mark a step towards the realization of a "desktop fab." Such tools enable
simple, flexible, high-throughput, and low-cost nano- and microscale patterning, which allow researchers to rapidly
synthesize and study systems ranging from nanoparticle synthesis to biological processes. We have developed a novel
scanning probe-based cantilever-free printing method termed polymer pen lithography (PPL), which uses an array of
elastomeric tips to transfer materials (e.g. alkanethiols, proteins, polymers) in a direct-write manner onto a variety of
surfaces. This technique takes the best attributes of dip-pen nanolithography (DPN) and eliminates many of the
disadvantages of contact printing. Various related techniques such as beam pen lithography (BPL), scanning probe block
copolymer lithography (SPBCL), and hard-tip, soft spring lithography (HSL) are also discussed.
Nanometer-scale patterning of graphite and graphene has been accomplished through local anodic oxidation
using an AFM tip. The underlying mechanism is explained. To date, protrusions, holes, trenches, and even
words have been patterned in HOPG over scales ranging from 1nm2 to 1mm2 and depths ranging from sub nm
to as deep as 200nm with less than 5 nm variation on the feature size and placement. This same method has
also been applied to CVD-grown graphene providing a resist-free process for patterning graphene at the single
nanometer scale. This capability could provide a method to rival e-beam lithography resolution but without any
pre- or post-processing.
We present progress towards scalable, high precision nanofabrication in a variety of materials using heated
Atomic Force Microscope (AFM) probes. Temperature control of a heated AFM tip allows nanometer scale thermochemical
patterning, deposition of thermoplastic polymers, and surface melting. The challenges that must be overcome to
scale such a technology to industrial-scale manufacturing include tip wear, thermal and mechanical control of the
cantilever, chemical reaction control at the tip-surface interface, and fabrication throughput. To mitigate tip wear, we
have integrated nanocrystalline diamond films onto our heated AFM probe tip. Such diamond tips are extremely resistant
to wear and fouling at a self-heating temperature of 400 C and load force of 200 nN over long distances. To improve
cantilever temperature control, a closed loop feedback control was designed to allow for 0.2 C precision temperature
control during nanolithography. Electrohydrodynamic jetting controls the deposition of polyethylene onto a heated probe
tip. Finally, to address throughput, we have fabricated cantilever arrays having independent temperature control and
integrated them into a commercial AFM system. We show these advances by patterning thousands of nanostructures of
polyethylene and poly(3-dodecylthiophene), with cumulative length more than 2 mm and patterning accuracy better than
Recent research results are presented where lasers of different pulse durations and wavelengths have been coupled to
near-field-scanning optical microscopes (NSOMs) through apertured bent cantilever fiber probes and atomic force
microscope (AFM) tips in apertureless configurations. Experiments have been conducted on the surface modification of
metals and semiconductor materials. By combining nanoscale ablative material removal with subsequent chemical
etching steps, ablation nanolithography and patterning of fused silica and crystalline silicon wafers has been
demonstrated. Confinement of laser-induced crystallization to nanometric scales has also been shown. In-situ observation of the nanoscale materials modification was conducted by coupling the NSOM tips with a scanning electron
microscope (SEM). Nucleation and growth of semiconductor materials have been achieved by laser chemical vapor
deposition (LCVD) at the nanoscale level. Locally selective growth of crystalline silicon nanowires with controlled size,
heterogeneity and nanometric placement accuracy has been accomplished.
Semiconductor nanomembranes, extremely thin (<10 to ~1000 nm) single-crystal sheets, promise considerable new
science and technology. They are flexible, they are readily transferable to other hosts and conform and bond easily, and
they can take on a large range of shapes (tubes, spirals, ribbons, wires) via appropriate strain engineering and patterning.
The ready ability to stack membranes allows the integration of the properties of different materials and/or orientations. A
brief review of nanomembrane fabrication and manipulation with a view toward different types of applications is provided.
Solid-state thermal neutron detectors are desired to replace 3He tube tube-based technology for the detection of special
nuclear materials. 3He tubes have some issues with stability, sensitivity to microphonics and very recently, a shortage of
3He. There are numerous solid-state approaches being investigated that utilize various architectures and material
combinations. Our approach is based on the combination of high-aspect-ratio silicon PIN pillars, which are 2 μm wide
with a 2 μm separation, arranged in a square matrix, and surrounded by 10B, the neutron converter material. To date, our
highest efficiency is ~ 20 % for a pillar height of 26 μm. An efficiency of greater than 50 % is predicted for our device,
while maintaining high gamma rejection and low power operation once adequate device scaling is carried out.
Estimated required pillar height to meet this goal is ~ 50 μm. The fabrication challenges related to 10B deposition and
etching as well as planarization of the three-dimensional structure is discussed.
THz and submillimeter wave technology is of great interest to DHS S&T due to the non-ionizing and clothing
penetrating properties of the spectral region. Imaging in the region allows for standoff imaging of concealed threats such
as Improvised Explosive Devices (IED) at operationally relevant distances. DHS S&T is investing in this area with the
development of components such as detectors and sources for active imaging as well as full sensor systems in the future.
The fundamental characterization of the region is also being explored with DHS funding by imaging well-characterized
rough surface scattering targets. Analysis of these images will yield data to be used in evaluating assumptions currently
made in current performance models. This along with the relevant field applications will be addressed.
The combination of atmospheric propagation windows and notches, in conjunction with the rich spectral signatures of
many materials in the millimeter-wave through THz region of the electromagnetic spectrum, make sensing and imaging
in this spectral range of particular interest in security, defense, and medical spheres. For sensing and imaging systems,
high-sensitivity and low-noise detectors are key components; micro- and nano-scale devices are especially promising for
detectors since small device scales naturally lead to lower device capacitances (and thus increased operational
frequency) while the exploitation of quantum mechanical tunneling at the nanoscale offers significant potential for
improving intrinsic detector performance. We report recent developments in InAs/AlSb/GaSb heterostructure backward
tunnel diodes for millimeter-wave through THz detection and imaging applications. These devices have demonstrated
measured room-temperature curvatures of 47 V-1, exceeding the fundamental limitation of q/kT=38.5 V-1 for Schottky
diodes. Since detector sensitivity is proportional to curvature, these increases in curvature translate to improved
sensitivity; unmatched sensitivities of 4600 V/W at 94 GHz have been measured, and sensitivities of nearly 50,000 V/W
are projected under conjugately-matched conditions. These devices also offer extremely low noise performance; we
report projected NEP values below 0.2 pW/Hz1/2 at 94 GHz for conjugately-matched detectors. A challenging issue in
the design of optimized interband tunneling-based devices is the difficulty in accurately simulating and modeling the
devices. We have developed a numerical model based on self-consistent solution of the Poisson/Schrodinger equations
coupled with 8-band k•p band structure and transfer-matrix calculations that agrees well with experimental device results
and enables projection of performance for novel structures. This simulation framework suggests several promising
avenues for further device performance improvement, and provides a means to optimize detector performance for
We describe the fabrication of an Orotron driven by a sheet beam of electrons. The sheet beam is generated by a carbon
nanotube field emission electron gun, which is less than 2 mm in total thickness. The orotron cavity is 2 cm long and 1
cm wide, and houses a microfabricated Smith-Purcell grating which generates the THz radiation. The sheet beam is 5
μm thick and 6 mm wide, and it travels within 15 μm of the top surface of the Smith-Purcell grating for the length of the
cavity. The Orotron is discretely tunable, which means that there are a number of cavity resonances that can be driven
by changing the energy of the beam such that for the period of the Smith-Purcell grating the cavity is driven on one of
the resonances. For this work, a target frequency of 0.5 THz, corresponding to a beam energy of 3 keV, was used.
We review our previous work to develop an uncooled THz detector capable of achieving an NEΔT ~0.5K at
30Hz frame rate and describe our approach to develop a staring THz camera based on a 2D array of such
detectors. Both predicted and measured results of performance metrics (responsivity, NEP, response time,
spectral bandwidth, NEΔT) are presented. The measured performance agrees reasonably well with predictions
and is consistent with attaining our NEΔT goal. Thus far, 1x4 detector arrays have been fabricated, and 1x8
focal plane arrays have been developed and tested. We briefly discuss our vision to achieve a128x128
detector array needed for a practical staring THz imager and describe the technology challenges needed to
The quantum cascade laser (QCL) is currently the only solid-state source of coherent THz radiation capable of
delivering more than 1 mW of average power at frequencies above
~ 2 THz. This power level combined with
very good intrinsic frequency definition characteristics make QCLs an extremely appealing solid-state solution
as compact sources for THz applications. I will present results on integrating QCLs with passive rectangular
waveguides for guiding and controlling the radiation emitted by the QCLs and on the performance of a THz
integrated circuit combining a THz QCL with a Schottky diode mixer to form a heterodyne receiver/transceiver.
THz technology has a rich history of use in the field of interstellar molecule identification where a variety of molecule
specific vibrational and rotational spectroscopic signatures exist and has been aggressively investigated for use in
advanced radar applications because of the immediate improvement in object resolution obtained at higher frequencies.
Traditionally, high power THz systems have relied upon millimeter wave sources and frequency multiplication
techniques to achieve acceptable output power levels, while lower power, table top spectroscopic systems, have relied on
broadband incoherent light sources. With the advent of high power lasers, advances in non-linear optics, and new
material systems, a number of promising techniques for the generation, detection and manipulation of THz radiation are
currently under development and are considered the enabling technologies behind a variety of advanced THz
This work presents a programmatic overview of current trends in THz technology of interest to a variety of government
organizations. It focuses on those techniques currently under investigation for the generation and detection of THz fields
motivated, for example, by such diverse applications as metamaterial spectroscopy, TH imaging, long standoff chem/bio
detection and THz communications. Examples of these new techniques will be presented which in turn will motivate the
need for the characterization of application specific active and passive THz components.
The characterization of anhydrous and hydrated forms of materials is of great importance to science and industry. Water
content poses difficulties for successful identification of the material structure by THz radiation. However, biological
tissues and hydrated forms of nonorganic substances still may be investigated by THz radiation. This paper outlines the
range of possibilities of the above characterization, as well as provides analysis of the physical mechanism that allows
or prevents penetration of THz waves through the substance. THz-TDS is used to measure the parameters of the
characterization of anhydrous and hydrated forms of organic and nonorganic samples. Mathematical methods (such as
prediction models of time-series analysis) are used to help identifying the absorption coefficient and other parameters of
interest. The discovered dependencies allow designing techniques for material identification/characterization (e.g. of
drugs, explosives, etc. that may have water content). The results are provided.
We present results on design, fabrication, and characterization of hot-electron bolometers based on low-mobility
two-dimensional electron gas (2DEG) in AlInN/GaN and AlGaN/GaN heterostructures. Electrical and optical
characterization of our Hot Electron Bolometers (HEBs) show that these sensors combine (i) high coupling to incident
THz radiation due to Drude absorption, (ii) significant electron heating by the THz radiation due to small value of the
electron heat capacity, (iii) substantial sensitivity of the device resistance to the heating effect. A low contact resistance
(below 0.5 Ω·mm) achieved in our devices ensures that the THz voltage primarily drops across the active region. Due to
a small electron momentum relaxation time, the inductive part of the impedance in our devices is large, so these sensors
can be combined with standard antennas or waveguides. In the capacity of the THz local oscillator (LO) for heterodyne
THz sensing, we fabricated AlGaAs/GaAs quantum cascade lasers (QCLs) with a stable continuous-wave single-mode
operation in the range of 2.5-3 THz. Spectral properties of the QCLs have been studied by means of Fourier transform
spectroscopy. It has been demonstrated that the spectral purity of the QCL emission line doesn't exceed the spectrometer
resolution limit at the level of 0.1 cm-1 (3 GHz). Discrete spectral tuning can be achieved using selective devices; fine
tuning can be done by thermally changing the refractive index of the material and by applied voltage. Compatibility of
the low-mobility 2DEG microbolometers with QCLs in terms of LO power requirements, spectral coverage, and cooling
requirements makes this technology especially attractive for THz heterodyne sensing.
Traditional THz electronics is using nonlinear properties of Schottky diodes for THz detectors and mixers and Gunn
diodes driving frequency multiplier Schottky diode chains. Recently, ultra-short channel silicon CMOS and nitridebased
transistors have demonstrated THz performance. New approaches use excitations of electron density in FET
channels - called plasma waves - to generate and detect THz radiation, and extremely high sheet electron density in
short channel AlN/GaN based HEMTs makes them especially suitable for applications in THz plasmonic devices.
Terahertz quantum cascade (QC) lasers are well suited for the exploration of active metamaterial concepts in the
terahertz frequency range. Terahertz composite right/left handed (CRLH) transmission line metamaterials can be
integrated with quantum cascade laser gainmaterial in order to compensate for losses, and enable laser waveguides
with new functionality. In particular, we consider the use of metamaterial transmission lines as travelling
wave antennas. After presenting the characteristics of a 2.5 THz quantum-cascade laser, calculated radiation
characteristics and beam patterns for a leaky-wave antenna based upon a balanced 1D CRLH transmission line
waveguide are shown.
The Naval Prototype Optical Interferometer (NPOI) is the longest baseline at visible wavelengths interferometer in the
world. The astronomical capabilities of such an instrument are being exploited and recent results will be presented. NPOI
is also the largest optical telescope belonging to the US Department of Defense with a maximum baseline of 435 meter
has a resolution that is approximately 181 times the resolution attainable by the Hubble Space Telescope (HST) and 118
times the resolution attainable by the Advanced Electro-Optical System (AEOS). It is also the only optical interferometer
capable of recombining up to six apertures simultaneously. The NPOI is a sparse aperture and its sensitivity is limited by
the size of the unit aperture, currently that size is 0.5 meters. In order to increase the overall sensitivity of the instrument
a program was started to manufacture larger, 1.4 meter, ultra-light telescopes. The lightness of the telescopes
requirement is due to the fact that telescopes have to be easily transportable in order to reconfigure the array. For this
reason a program was started three years ago to investigate the feasibility of manufacturing Carbon Fiber Reinforced
Polymer (CFRP) telescopes, including the optics. Furthermore, since the unit apertures are now much larger than r0 there
is a need to compensate the aperture with adaptive optics (AO). Since the need for mobility of the telescopes, compact
AO systems, based on Micro-Electro-Mechanical-Systems (MEMS), have been developed. This paper will present the
status of our adaptive optics system and some of the results attained so far with it.
Thin-shelled composite mirrors have been recently proposed as both deformable
mirrors for aberration correction and as variable radius-of-curvature mirrors for
adaptive optical zoom. The requirements on actuation far surpass those for other
MEMS or micro-machined deformable mirrors. We will discuss recent progress
on developing the actuation for these mirrors, as well as potential applications.
We are developing a highly miniaturized trapped ion clock to probe the 12.6 GHz hyperfine transition in the
171Yb+ ion. The clock development is being funded by the Integrated Micro Primary Atomic Clock
Technology (IMPACT) program from DARPA where the stated goals are to develop a clock that consumes
50 mW of power, has a size of 5 cm3, and has a long-term frequency stability of 10-14 at one month. One of
the significant challenges will be to develop miniature single-frequency lasers at 369 nm and 935 nm and the
optical systems to deliver light to the ions and to collect ion fluorescence on a detector.
Polarimetric imaging captures the polarization state of light from all the points of a scene.
Snapshot polarimetric imaging collects the Stokes' parameters spatial distribution
simultaneously. We will discuss state-of-the-art achievements and some fundamental
diffraction limitations in polarimetric imaging with an array of micro-components. We will
also look at the natural vision system of the mantis shrimp, with many of these same sensing
abilities. The evolved and exquisite vision system possesses a recently-discovered circular
polarization capability. This comprehensive polarization vision may enable
imaging/communicating advantages in the underwater environment as well as more general
turbid environments such as smoke and fog.
We present a review on recent advancements in rolled-up optical components created using strain engineering. A look at
optical and optofluidic resonators as well as the hyperlens and an optical fiber metamaterial device is given. These
individual ultra-compact components allow researchers to develop large arrays of a future highly-integrated biological
sensing device known as a lab-in-a-tube. These lab-in-a-tube devices would allow for a very large parallel but individual
analysis of thousands of cells, molecules and bacteria on a single chip.
We have integrated electronic, optical, magnetic, thermal and fluidic devices into systems to construct useful analysis
tools. Over the past several years, we have developed soft lithography approaches to define microfluidic systems in
which pico-Liter volumes can be manipulated. These fluidic delivery systems have more recently been integrated with
optical and electronic devices. We have also developed thermal control systems with fast (>50oC/s) cooling and heating
ramp speeds and excellent accuracy.
We examine light-trapping in thin crystalline silicon periodic nanostructures for solar cell applications. Using group
theory, we show that light-trapping can be improved over a broad band when structural mirror symmetry is broken. This
finding allows us to obtain surface nanostructures with an absorptance exceeding the Lambertian limit over a broad band
at normal incidence. Further, we demonstrate that the absorptance of nanorod arrays with symmetry breaking not only
exceeds the Lambertian limit over a range of spectrum but also closely follows the limit over the entire spectrum of
interest for isotropic incident radiation. These effects correspond to a reduction in silicon mass by two orders of
magnitude, pointing to the promising future of thin crystalline silicon solar cells.
Photonic nanostructures with widely, rapidly and reversibly tunable diffraction in the visible and near-infrared spectrum
can be created through a magnetic field assisted assembly strategy. We first describe the mechanism for the formation of
dynamic photonic chains and the tuning of the diffraction colors using an external magnetic field. Then we discuss the
fixation of photonic chains in a solid polymer matrix through combining instant magnetic assembly with a rapid UV
polymerization process which allows us to confirm the chaining structures. Finally, we demonstrate several applications of
magnetically tunable photonic nanostructures for security and sensing devices, high resolution patterning of multiple
The U.S. Army has strong interests in nanoscale architectures that enable enhanced extraction and controllable
multiplication of the THz/IR regime spectral signatures associated with specific bio-molecular targets. Emerging DNAbased
nano-assemblies (i.e., either materials or structural devices) will be discussed that realize novel sensing paradigms
through the incorporation of organic and/or biological molecules such that they effect highly predictable and controllable
changes into the electro-optical properties of the resulting superstructures. Results will be given to illustrate the utility of
functionalized DNA materials in biological (and chemical) sensing, and to demonstrate how the basic science can be
leveraged to study and develop synthetic antibodies, reporters and vaccines for future medical applications.
The engineered deposition of self-assembled coatings of micro- and nano-particles on solid surfaces has applications in
photonic crystals, optoelectronic devices, sensors, waveguides and antireflective coatings. Besides lithographic, etching
or vapor deposition methods, these coatings can be self-assembled on small (<O(1mm2) circular surfaces by the
deposition and drying of drops on surfaces, or on larger (O(cm2)) rectangular surfaces by pulling an evaporating
meniscus, in a process called convective deposition. Both processes involve multiscale phenomena such as transient
fluid dynamics with wetted regions, DLVO forces, heat and mass transfer in the deforming geometry of a complex fluid.
These competing phenomena control the self-assembly of micro- and nano-particle deposits. A simple phase diagram is
presented, that describes the mechanisms governing the transition between different patterns during the evaporation of a
drop. A multiphysics modeling of the convective deposition process is also presented, which provides insight on ways to
improve the reliability of the deposition process. Finally, an outlook is given on technical applications related to the use
of convective deposition techniques in manufacturing.
Graphene is well known for its outstanding electronic, thermal, and mechanical properties, and has recently gained
tremendous interest as a nanomaterial for optoelectronic devices. We review our recent efforts on exfoliated graphene
with a particular focus on the influence of graphene's chiral edges on the electronic and optical properties. We first
show that Raman spectroscopy can not only be used for layer metrology but also to monitor the composition of
graphene's zigzag/armchair edges. To elucidate the role of the localized edge state density, we fabricated dye
sensitized antidot superlattices, i.e. nanopatterned graphene. The fluorescence from deposited dye molecules was
found to quench strongly as a function of increasing antidot filling fraction, whereas it was enhanced in unpatterned
but electrically back-gated samples. This contrasting behavior is strongly indicative of a built-in lateral electric field of
up to 260 mV accounting for p-type doping as well as fluorescence quenching due to dissociation of electron-hole
pairs from attached dye molecules. Our study provides new insights into the interplay of localized edge states in
antidot superlattices and the resulting band bending, which are critical properties to enable novel applications of
nanostructured graphene for light harvesting and photovoltaic devices.
This paper describes the results of a Joint Experiment performed on behalf of the MAST CTA. The system developed for the Joint Experiment makes use of three robots which work together to explore and map an unknown environment. Each of the robots used in this experiment is equipped with a laser scanner for measuring walls and a camera for locating doorways. Information from both of these types of structures is concurrently incorporated into each robot's local map using a graph based SLAM technique.
A Distributed-Data-Fusion algorithm is used to efficiently combine local maps from each robot into a shared global map. Each robot computes a compressed local feature map and transmits it to neighboring robots, which allows each robot to merge its map with the maps of its neighbors. Each robot caches the compressed maps from its neighbors, allowing it to maintain a coherent map with a common frame of reference.
The robots utilize an exploration strategy to efficiently cover the unknown environment which allows collaboration on an unreliable communications channel. As each new branching point is discovered by a robot, it broadcasts the information about where this point is along with the robot's path from a known landmark to the other robots. When the next robot reaches a dead-end, new branching points are allocated by auction. In the event of communication interruption, the robot which observed the branching point will eventually explore it; therefore, the exploration is complete in the face of communication failure.
There are many examples in nature where large groups of individuals are able to maintain three-dimensional formations
while navigating in complex environments. This paper addresses the development of a framework and robot controllers
that enable a group of aerial robots to maintain a formation with partial state information while avoiding collisions. The
central concept is to develop a low-dimensional abstraction of the large teams of robots, facilitate planning, command, and
control in a low-dimensional space, and to realize commands or plans in the abstract space by synthesizing controllers for
individual robots that respect the specified abstraction.
The fundamental problem that is addressed in this paper relates to coordinated control of multiple UAVs in close
proximity. We develop a representation for a team of robots based on the first and second statistical moments of the
system and design kinematic, exponentially stabilizing controllers for point robots. The selection of representation permits
a controller design that is invariant to the number of robots in the system, requires limited global state information, and
reduces the complexity of the planning problem by generating an abstract planning and control space determined by the
moment parameterization. We present experimental results with a team of quadrotors and discuss considerations such as
aerodynamic interactions between robots.
Unmanned micro air vehicles (MAVs) will play an important role in future reconnaissance and search and rescue applications.
In order to conduct persistent surveillance and to conserve energy, MAVs need the ability to land, and they need
the ability to enter (ingress) buildings and other structures to conduct reconnaissance. To be safe and practical under a
wide range of environmental conditions, landing and ingress maneuvers must be autonomous, using real-time, onboard
sensor feedback. To address these key behaviors, we present a novel method for vision-based autonomous MAV landing
and ingress using a single camera for two urban scenarios: landing on an elevated surface, representative of a rooftop,
and ingress through a rectangular opening, representative of a door or window. Real-world scenarios will not include special
navigation markers, so we rely on tracking arbitrary scene features; however, we do currently exploit planarity of the
scene. Our vision system uses a planar homography decomposition to detect navigation targets and to produce approach
waypoints as inputs to the vehicle control algorithm. Scene perception, planning, and control run onboard in real-time;
at present we obtain aircraft position knowledge from an external motion capture system, but we expect to replace this in
the near future with a fully self-contained, onboard, vision-aided state estimation algorithm. We demonstrate autonomous
vision-based landing and ingress target detection with two different quadrotor MAV platforms. To our knowledge, this is
the first demonstration of onboard, vision-based autonomous landing and ingress algorithms that do not use special purpose
scene markers to identify the destination.
This paper presents the development of a static estimator for obtaining state information from optic flow and
radar measurements. It is shown that estimates of translational and rotational speed can be extracted using a
least squares inversion. The approach is demonstrated in a simulated three dimensional urban environment on an
autonomous quadrotor micro-air-vehicle (MAV). The resulting methodology has the advantages of computation
speed and simplicity, both of which are imperative for implementation on MAVs due to stringent size, weight,
and power requirements.
Autonomous small robotic platforms require a suite of sensor to navigate and function in complex environment. Due to
limited space, onboard power, and processing capability these sensors must be low mass, compact size, low power, and
run with minimal processing resources. We are in the process of developing a compact and low-power imaging mm-wave
radar system for small autonomous robotic platforms operating at Y-band to allow for navigation and obstacle
detection in conditions that make the use of passive optical sensors difficult or impossible. The radar system is being
fabricated and assembled using silicon micromachining technique with the overall mass of 5 grams, peak power of 200
mW, and operational power of 6.7 mW for one frame per second update rate, field of view of ± 25°, angular resolution
of 2°, range resolution of 37.5cm, and range of 400m. The beam steering is accomplished by frequency scanning and the
range resolution is obtained from the standard FMCW technique utilizing a chirped signal waveform with step
discontinuities. This paper will present the overall architecture of this radar system in addition to the phenomenological
investigation of scattering from obstacle in indoor environment. It is also shown how radar images taken from indoor
scenes can be interpreted and utilized to create the interior layout of a building.
Nanometer CMOS processes have proven to be surprisingly effective for analog and RF design. New design techniques
have greatly improved the efficiency of ADCs and RF interfaces and also enabled new flexibility. Moving to techniques
that are more digital in nature allows fast and easy changes in architecture and performance. Furthermore, from the
standpoint of energy efficiency there can be fundamental advantages to processing signals in the digital domain. This
paper discusses digital dominant nanometer CMOS transmitter and receiver schemes that are the basis of flexible
efficient wireless transceivers for the MAST platforms.
This paper presents recent work on reconfigurable all-digital radio architectures. We leverage the flexibility and
scalability of synthesized digital cells to construct reconfigurable radio architectures that consume significantly less
power than a software defined radio implementing similar architectures. We present two prototypes of such architectures
that can receive and demodulate FM and FRS band signals. Moreover, a radio architecture based on a reconfigurable alldigital
phase-locked loop for coherent demodulation is presented.
Radio signal strength (RSS) is a reasonable proxy for link quality, but its accurate estimation requires frequency and spatial diversity due to fluctuation caused by fading. We consider a Rayleigh/Rician fading model, and gather RSS measurements during motion in a complex environment to enable gradient estimation. Using the RSS gradient, we develop control laws to track active sources. These may be used to establish and preserve connectivity among collaborative autonomous agents, to locate and approach radio sources, as well as deploying agents to assist mobile ad hoc networks (MANETs).
Ad hoc communication among small robotic platforms in complex indoor environment is further challenged by three
limiting factors: 1) limited power, 2) small size antennas, and 3) near-ground operation. In complex environments such
as indoor scenarios often times the line-of-sight communication cannot be established and the wireless connectivity must
rely on multi-path propagation. As a result, the propagation path-loss is much higher than free-space, and more power
will be needed to obtain the need coverage. Near ground operation also leads to increased path-loss. To maintain the
network connectivity without increasing the required power a novel high gain miniaturized radio repeater is presented.
Unlike existing repeater systems, this system utilizes two closely spaced low profile miniaturized planar antennas
capable of producing omnidirectional and vertical radiation patterns as well as a channel isolator layer that serves to
decouple the adjacent antennas. The meta-material based channel isolator serves as an electromagnetic shield, thus
enabling it to be built in a sub-wavelength size of 0.07λ0
2 × λ0/70, the smallest repeater ever built. Also wave propagation
simulations have been conducted to determine the required gain of such repeaters so to ensure the signal from the
repeater is the dominant component. A prototype of the small radio repeater is fabricated to verify the design
performance through a standard free-space measurement setup.
This paper reviews currently recognized needs for advances in precision navigation and timing technology, summarizes
ongoing efforts, and discusses future technological developments being pursued under the aggregated
DARPA/MTO Microtechnology for Positioning, Navigation, and Timing (micro-PNT) program.
Recent years have witnessed breakthrough researches in micro- and nano-mechanical resonators with small dissipation.
Nano-precision micromachining has enabled the realization of integrated micromechanical resonators with record high Q
and high frequency, creating new research horizons. Not too long ago, there was a perception in the MEMS community
that the maximum f.Q product of a microresonator is limited to a frequency-independent constant determined by the
material properties of the resonator. In this paper, the contribution of phonon interactions in determining the upper limit
of f.Q product in micromechanical resonators will be discussed and shown that after certain frequency, the f.Q product is
no longer constant but a linear function of frequency. This makes it possible to reach very high Qs in GHz micro- and
nano-mechanical resonators and filters. Contributions of other dissipation mechanisms such as thermoelastic damping
and support loss in the quality factor of a microresonator will be discussed as well.
Single monolayers of molecules were found to strongly affect the quality factors of MHz-range torsional silicon
resonators. By changing a single monolayer of molecules on the surface of a 5-μm-wide, 250-nm-thick silicon resonator
- less than 0.07% of the total mass - the quality factor of the resonator was increased by 70%. In contrast, the standard
commercial coating, a thin layer of silicon oxide, dissipates at least 75% of the mechanical energy in similarly sized
resonators. Since the relative importance of these surface chemical losses scales with the resonator's surface-to-volume
ratio, the development of low-loss, stable surface chemistries will be important for the production of high-performance
micro- and nano-mechanical devices.
The contribution is directed to providing accurate simulation and approximation of the Q-factor determined by thermalelastic
damping in complex micro-electromechanical (MEM) resonators. The base model created is presented as a
system of partial differential equations, which describe the elastic and thermal phenomena in the MEM structure. The
FEM calculations were performed by using COMSOL Multiphysics software. The model was verified by comparing
numerically and analytically obtained damped modal properties of a MEM cantilever resonator. The comparison of
calculated and experimentally obtained resonant frequencies and Q-factor values indicated a good agreement of
tendencies of change of the quantities against temperature. Investigation of longitudinal and bending vibration modes in
3D of a beam resonators was accomplished by taking into account the layered structure of the resonator and the influence
of the geometry of the clamping zone. Modal properties of rectangle- and ring-shaped bulk-mode MEM resonators were
In micro- and nano-scale resonators, a key performance metric is the quality factor (Q), which is the ratio of
stored mechanical energy to the energy dissipated. In well-optimized designs, Q is limited by thermal physics
and specific energy loss mechanisms including thermoelastic, Akhieser, and Landau-Rumer damping. The
relative importance of each effect depends on the time and length scales dominating the device. Most published
analyses focus on special regimes where only one mechanism dominates, though real devices may operate in
regimes that are not the limiting case. This paper presents thermal damping across the range of frequency and
length scales. Data on acoustic loss is compared with theory.
While Sandia initially was motivated to investigate emergent microsystem technology to miniaturize existing macroscale
structures, present designs embody innovative approaches that directly exploit the fundamentally different material
properties of a new technology at the micro- and nano-scale. Direct, hands-on experience with the emerging technology
gave Sandia engineers insights that not only guided the evolution of the technology but also enabled them to address new
applications that enlarged the customer base for the new technology. Sandia's early commitment to develop complex
microsystems demonstrated the advantages that early adopters gain by developing an extensive design and process tool
kit and a shared awareness of multiple approaches to achieve the multiple goals.
As with any emergent technology, Sandia's program benefited from interactions with the larger technical community.
However, custom development followed a spiral path of direct trial-and-error experience, analysis, quantification of
materials properties at the micro- and nano-scale, evolution of design tools and process recipes, and an understanding of
reliability factors and failure mechanisms even in extreme environments. The microsystems capability at Sandia relied
on three key elements. The first was people: a mix of mechanical and semiconductor engineers, chemists, physical
scientists, designers, and numerical analysts. The second was a unique facility that enabled the development of custom
technologies without contaminating mainline product deliveries. The third was the arrival of specialized equipment as
part of a Cooperative Research And Development Agreement (CRADA) enabled by the National Competitiveness
Technology Transfer Act of 1989. Underpinning all these, the program was guided and sustained through the research
and development phases by accomplishing intermediate milestones addressing direct mission needs.
This paper describes recent advances in the MEMS
performance challenges with emphases on packaging and
shock tests. In the packaging area, metal to metal bonding
processes have been developed to overcome limitations of
the glass frit bonding by means of two specific methods:
(1) pre-reflow of solder for enhanced bonding adhesion,
and (2) the insertion of thin metal layer between parent
metal bonding materials. In the shock test area, multiscale
analysis for a MEMS package system has been
developed with experimental verifications to investigate
dynamic responses under drop-shock tests. Structural
deformation and stress distribution data are extracted and
predicted for device fracture and in-operation stiction
analyses for micro mechanical components in various
MEMS sensors, including accelerometers and gyroscopes.
Hydraulic induced fracturing (HIF) in oil wells is used to increase oil productivity by making the subterranean terrain
more deep and permeable. In some cases HIF connects multiple oil pockets to the main well. Currently there is a need to
understand and control with a high degree of precision the geometry, direction, and the physical properties of fractures.
By knowing these characteristics (the specifications of fractures), other drill well locations and set-ups of wells can be
designed to increase the probability of connection of the oil pockets to main well(s), thus, increasing productivity. The
current state of the art of HIF characterization does not meet the requirements of the oil industry. In Mexico, the
SENER-CONACyT funding program recently supported a three party collaborative effort between the Mexican
Petroleum Institute, Schlumberger Dowell Mexico, and the Autonomous University of Juarez to develop a sensing
scheme to measure physical parameters of a HIF like, but not limited to pressure, temperature, density and viscosity. We
present in this paper a review of HIF process, its challenges and the progress of sensing development for down hole
measurement parameters of wells for the Chicontepec region of Mexico.
MicroElectroMechanical Systems (MEMS) have become commercially successful in a number of niche applications.
However, commercial success has only been possible where design, operating conditions, and materials result in devices
that are not very sensitive to tribological effects. The use of MEMS in defense and national security applications will
typically involve more challenging environments, with higher reliability and more complex functionality than required
of commercial applications. This in turn will necessitate solutions to the challenges that have plagued MEMS since their
inception - namely, adhesion, friction and wear. Adhesion during fabrication and immediately post-release has largely
been resolved using hydrophobic coatings, but these coatings are not mechanically durable and do not inhibit surface
degradation during extended operation.
Tribological challenges in MEMS and approaches to mitigate the effects of adhesion, friction and wear are discussed. A
new concept for lubrication of silicon MEMS using gas phase species is introduced. This "vapor phase lubrication"
process has resulted in remarkable operating life of devices that rely on mechanical contact. VPL is also an effective
lubrication approach for materials other than silicon, where traditional lubrication approaches are not feasible. The
current status and remaining challenges for maturation of VPL are highlighted.
Medicine is clearly becoming one of the major challenges in the field of Applied Physics. The development of novel
pharmaceutical devices, such as diagnostics, drug carriers or vaccines is growingly dependant on nanotechnology
processes. Nanotechnology and MicroElectroMechanical Systems (MEMS) applied to biological issues have given rise
to unprecedented biomimetic designs, which are leading the development of innovative tools, including high-throughput
platforms for combinatorial bioassays, or microfluidics-based systems for the detection of diseases. This talk will
address the use of MEMS and nanotechnology as a powerful combination for improving Public Health items,
specifically through novel diagnostic systems for a wide set of human diseases. Also, we herein present our work
involving the use of this approach for the development of a point-of-care test to detect tuberculosis, an infectious disease
caused by Mycobacterium tuberculosis, one of the most evasive germs considered as potential biological warfare agents.
High performance thermoelectric materials in a wide range of temperatures are essential to broaden the application
spectrum of thermoelectric devices. This paper presents experiments on the power and efficiency characteristics of lowand
mid-temperature thermoelectric materials. We show that as long as an appreciable temperature difference can be
created over a short thermoelectric leg, good power output can be achieved. For a mid-temperature n-type doped
skutterudite material an efficiency of over 11% at a temperature difference of 600 °C could be achieved. Besides the
improvement of thermoelectric materials, device optimization is a crucial factor for efficient heat-to-electric power
conversion and one of the key challenges is how to create a large temperature across a thermoelectric generator
especially in the case of a dilute incident heat flux. For the solar application of thermoelectrics we investigated the
concept of large thermal heat flux concentration to optimize the operating temperature for highest solar thermoelectric
generator efficiency. A solar-to-electric power conversion efficiency of ~5% could be demonstrated. Solar
thermoelectric generators with a large thermal concentration which minimizes the amount of thermoelectric
nanostrucutured bulk material shows great potential to enable cost-effective electrical power generation from the sun.
This paper presents our recent results on carbon nanomaterials for applications in energy storage and bio-sensor. More
specifically: (i) A novel binder-free carbon nanotubes (CNTs) structure as anode in Li-ion batteries. The interfacecontrolled
CNT structure, synthesized through a two-step chemical vapor deposition (CVD) and directly grown on
copper current collector, showed very high specific capacity - almost three times as that of graphite, excellent rate
capability. (ii) A large scale graphene film was grown on Cu foil by thermal chemical vapor deposition and transferred to
various substrates including PET, glass and silicon by using hot press lamination and etching process. The graphene/PET
film shows high quality, flexible transparent conductive structure with unique electrical-mechanical properties; ~88.80 %
light transmittance and ~ 100 Ω/sq sheet resistance. We demonstrate application of graphene/PET film as flexible and
transparent electrode for field emission displays. (iii) Application of individual carbon nanotube as nanoelectrode for
high sensitivity electrochemical sensor and device miniaturization. An individual CNT is split into a pair of
nanoelectrodes with a gap between them. Single molecular-level detection of DNA hybridization was studied.
Hybridization of the probe with its complementary strand results in an appreciable change in the electrical output signal.
Two technologies for MEMS (Microelectromechanical Systems) scale cell formation are discussed. First, the
fabrication of planar alkaline cell batteries compatible with MEMS scale power storage applications is shown. Both mm
scale and sub-mm scale individual cells and batteries have been constructed. The chosen coplanar electrode geometry
allows for easy fabrication of series connected cells enabling higher voltage while simplifying the cell sealing and
electrode formation. The Zn/Ag alkaline system is used due to the large operating voltage, inherent charge capacity,
long shelf life, and ease of fabrication. Several cells have been constructed using both plated and spun-on silver. The
plated cells are shown to be limited in performance due to inadequate surface area and porosity; however, the cells made
from spun-on colloidal silver show reasonable charge capacity and power performance with current densities of up to
200 uA/mm2 and charge capacities of up to 18 mA-s/mm2. Second, a new printing method for interdigitated 3-D cells is
introduced. A microfluidic printhead capable of dispensing multiple materials at high resolution and aspect ratio is
described and used to form fine interdigitated cell features which show >10 times improvement in energy density.
Representative structures enabled by this method are modeled, and the energy and power density improvements are
Flexible electronics require flexible energy storage, and electrochemical
batteries are currently the strongest option for such devices. We further our
previous investigation, beginning to add quantitative analysis to the composite
mechanical/electrochemical performance of printed electrodes. The presented
work will explain the principles of microfluidic stress analysis and how it provides
insight into the operating conditions of real microbatteries.
Building battery architectures with functional interfaces that are interpenetrated in three dimensions opens
the door to major gains in performance as compared to conventional 2-D battery designs, particularly with respect to
the battery footprint. We are developing 3-D solid-state Li-ion batteries that are sequentially assembled from
interpenetrating and tricontinuous networks of anode, cathode, and electrolyte/separator materials. We use fiberpaper-
supported carbon nanofoams as a massively parallel, conductive, ultraporous base platform within which to
create the 3-D cell. The components required for battery operation are incorporated into the x,y,z-scalable papers
and include nanoscale coatings of metal oxides that serve as Li-ion-insertion electrodes and ultrathin, electroninsulating/
Li-ion conducting polymer coatings that serve as the electrolyte/separator.
Compound semiconductors offer significant advantages over silicon in photovoltaics due to their direct bandgaps, ability
to form multijunction solar cells, as well as superior radiation hardness. However, costs for growth and integration of
these materials have been prohibitively high, thereby limiting their large-scale implementation in terrestrial
photovoltaics. Here we review materials growth and fabrication strategies that were recently developed to address many
of these challenges by employing device-quality, multilayer epitaxial assemblies of compound semiconductors in the
manner that enables sequential release of respective functional layers as well as reuse of the growth substrate. This new
approach combined with techniques of micro-transfer printing provides a practical and cost-effective route to implement
high quality compound semiconductors in terrestrial photovoltaics but also opens up new application possibilities and
modes of use that have not been possible with conventional technologies.