name of honor or award - Northwestern University

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NOMINATION FOR ASME SOCIETY AWARDS
1.
NAME OF HONOR OR AWARD
2.
DATES
Submitted
Nadai Medal
01/27/2010
Received
(To be filled in by ASME)
3.
FULL NAME OF NOMINEE OR AUTHOR
Horacio Dante Espinosa
ASME Membership or Grade of Nominee/Author
Nominee's/Author's Current Position
Nominees /Author's Address
(business)
Fellow
Date of Birth
11/17/57
James and Nancy Farley Professor of Mechanical Engineering
Mechanical Engineering
Northwestern University
2145 Sheridan Rd.
Evanston, IL 60208-3111
Nominee's/Author's Citizenship (optional)
4.
USA
CITATION/TITLE (35-40 word summary of nominee's qualifications. Since it is Society policy not to give more than
one award for a given set of achievements, do not make the citation so overarching that future awards are
precluded.)
For contributions to size scale plasticity, in-situ transmission electron microscopy identification of fracture of
multiwalled carbon nanotubes, development of atomic force microcopy probes for the direct patterning of organic and
inorganic molecules and failure identification and modeling of ceramics and biomaterials
5.
NOMINATOR(S) (Name(s), ASME committee connections, professional acquaintanceships)
Ted Belytschko , ASME Fellow, Colleague of Prof. Espinosa at Northwestern University
6.
REFERENCES (Names and addresses of the four or five individuals acquainted with nominee's qualifications and
requirements of the award who will complete reference forms Click here for reference form. At least two of the
references must be members of ASME and no more than one should come from the nominee’s organization. Please
be advised that the Committee will not consider more than five reference forms. It is the responsibility of the nominator
to provide reference forms to the individuals supporting the nomination).
Alan Needleman, Brown University. 182 Hope Street. City Providence, RI 02912
David McDowel, Georgia Institute of Technology, 4105 MRDC, GWW School of Mech. Engng, Atlanta, GA
30332-0405
John Hutchinson, Harvard University. 29 Oxford Street, Cambridge, MA
Jan Achenbach, Northwestern University, 2137 N Tech Drive, #330, Evanston, IL 60208
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QUALIFICATIONS: Give complete statements of the specific ways in which the nominee meets the
requirements for the honor. Be sure to support all claims made on the individual's accomplishments.
Espinosa is widely regarded as one of the most prominent, creative and diversely talented investigators of
his generation with a strong record of contributions to the field of mechanics of materials. He has achieved
worldwide recognition for his pioneering work on size effects and scaling of plasticity and fracture of
submicron freestanding thin films. He was the first to show that, as the characteristic dimensions of the
specimen decrease below a threshold, the strength and hardening rate increase, even in the absence of
strain gradients. Furthermore, by using 3-D discrete dislocation models, his work revealed the role of
dislocation nucleation and escape through surfaces in the observed strengthening phenomenon. His most
recent discrete dislocation dynamics work on size scale plasticity of submicron micropillars confirmed
analytically derived scaling laws and provided insight into the dislocation source activation and shut down
mechanisms responsible for the staircase stress-strain response observed in experiments. Espinosa’s
contributions originate from a set of novel tools and techniques developed by him and his students (see
table below). Selected developments leading to these contributions are summarized next.
Contribution
Core Tool/Technique
Novelty of Approach
First demonstration of
size effects and scaling of
plasticity in freestanding
thin films
Membrane Deflection Experiment
(MDE)
Use of microfabrication and a
nanoindenter to create a welldefined pure tensile loading at the
microscale
Measurement of true
mechanical properties in
CNTs and NWs
MEMS-based material testing
system for in-situ SEM/TEM
characterization of 1-D
nanostructures
Well-defined electrical/mechanical
loading with simultaneous
displacement measurement and in
situ SEM/TEM imaging
Direct-write probe-based
nanopatterning of
biomolecules, functional
nanoparticles, and sol-gel
Nanofountain Atomic Force
Microscopy Probes for direct-write
nanofabrication
Combines sub-100-nm patterning
resolution with broad patterning
capabilities (biomolecules,
nanoparticles, etc. in liquid solution)
Feedback-controlled
carbon nanotube-based
nanoelectromechanical
switch
In-situ SEM construction and
characterization of
electromechanical response of
cantilevered carbon nanotube
device
Use of feedback control of tunneling
current to achieve bistable
switching; multiphysics modeling of
device performance
Underwater blast
experiments on scaled
structures
Fluid-structure interaction setup
with specimen mounted against a
water chamber and use of a flyer
plate to generate impulsive loads
Use of scaling analysis to achieve a
laboratory scale apparatus that can
capture essential features in the
deformation and failure of scaled
naval structures
Size Effects in Thin Films and other Small Scale Systems
Espinosa achieved worldwide recognition for his pioneering work on size effects and scaling of plasticity
and fracture in submicron freestanding face center cubic metallic thin films. He was the first to identify the
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effect of film thickness on tensile strength and hardening rate, in the absence of strain gradients, by means
of a novel membrane deflection experiment. The MDE uses a nanoindenter as a loading device and
microfabrication to make freestanding submicron specimens, see Fig. 1. This work was first published in
three conference proceeding in 2001, SEM June 2001, MRS Fall 2001, ASME Interpack’01 and later in JMPS,
in 2003 and 2004. While size scale plasticity in thin films was previously demonstrated by means of wafer
curvature measurements or cantilever bending experiments, this work is unique in several respects: a) the
tests were performed in pure tension (absence of loading gradients); b) they were performed in submicron
freestanding films (no interfaces that can pile up dislocations); c) the test was instrumented with a Mireau
microscope such that film deformation, localization and fracture were observed and correlated to stressstrain behavior in real time. The test was later extended to measure fracture toughness in thin films
(Espinosa and Peng, JMEMS, Vol. 14, p. 153, 2005) and to identify properties of nanomaterials, e.g.,
applicability of Weibull theory to nanocrystalline diamond, amorphous diamond, and single crystal SiC films
(JAP, Vol. 94, No. 9, p. 6076, 2005; APL, Vol. 89, No. 7, p. 73111, 2006; JMR, Vol. 22, No. 4, 2007).
Line-load Tip
Wafer
Microscope
Objective
Figure 1: Membrane deflection experimental set up and SEM image of fractured gold thin film
Using 3-D discrete dislocation dynamics simulations, his group showed the role of dislocation nucleation
and escape through surfaces in the observed thin films and micropillar strengthening phenomenon.
Espinosa’s most recent discrete dislocation dynamics work on size scale plasticity of submicron micropillars
confirmed analytically derived scaling laws and provided insight into the dislocation source activation and
shut down mechanisms responsible for the staircase stress-strain response observed in micropillar
experiments (Tang et al., PRL, 2008). The article provides the first detailed mechanistic interpretation of
the starvation hypothesis advanced by W. Nix and the peculiar stress-strain behavior observed in metallic
micropillar compression experiments. A unique feature of the article is the generation of stable 3-D
networks of dislocations by means of simulated annealing rather than by the artificial introduction of
Frank-Read sources.
Mechanical Properties of 1-D Nanostructures
Espinosa and students designed and built novel microsystems for in-situ electron microscopy testing of thin
films, carbon nanotubes (CNTs) and nanowires (NWs). The MEMS-based material system (Fig. 2A) is the
world first to provide electronic measurement of load and deformation while allowing simultaneous
acquisition of high resolution images of the atomic structure of test specimens within the SEM/TEM.
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Electronic actuation and sensing are integrated in a single microelectromechnaical system (Zhu and
Espinosa, PNAS 2005) providing a complete nano scale testing apparatus. Load is measured electronically,
with resolution of about 10 nano-Newtons, based on differential capacitive sensing while loading under
displacement control is achieved by means of thermal actuation. When the system is placed in a
transmission electron microscope (TEM, see Fig. 2B), high resolution atomic images of the specimen can be
obtained in real time without the need for shifting the electron beam. The implication is that a number of
nanostructures, with characteristic dimensions smaller than 100 nm, can be tested and failure modes at
the atomic level identified. To put this in perspective, note that other microfabricated devices for in-situ
testing, previously reported in the literature, are not true MEMS in the sense that they do not couple
mechanical and electronic fields to accomplish loading and its measurement. For instance, microfabricated
loading frames are based only on mechanical deformation. They do not posses independent electronic
measurement of load and load application is not integrated into one micro device. This has several
implications with the most significant being the requirement of having to move and/or change the
magnification of the electron beam to determine load. As a result, simultaneous observation of atomic
defects and load measurement are not possible. As the popularity of nanoscale mechanical
characterization of materials increases, the superiority of the m-MTS will become pervasive. The microMTS concept is applicable to the characterization of mechanical, thermal and electro-mechanical
properties not only of metallic/semiconducting nanowires and carbon nanotubes but also of a large
number of organic and inorganic nanomaterials.
A)
C1 C2
C3
B)
Figure 2: A) SEM images of a nano-material testing system (n-MTS). Left: Displacement-controlled system
with thermal actuator and electrostatic load sensor. The specimen is mounted in the gap between these
two elements. Right: Mounting a nanowire on the device using a piezoelectric nanomanipulator with
tungsten probe and electron beam induced deposition (EBID) of platinum. B) Customized TEM holder
designed to hold and electronically access the n-MTS chip for in-situ TEM experiments. The holder tip and
n-MTS are shown in the inset.
Employing this technology, the Espinosa group provided the first direct correlation between failure stress
and number of failed shells in multiwalled carbon nanotubes. Failure modes and carbon atomic structures
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(inter-shell cross-linking) were also identified as a function of exposure dose to electron or ion radiation.
The reason for this phenomenon is that inter-shell cross-linking occurs during growth or during specimen
radiation with electrons or ions possessing energy above a certain threshold (energy for vacancy formation
in the carbon shell). While cross-linking was hypothesized prior to this work, there was no direct imaging of
atomic structure or correlation to measurements of associated load-displacement curves (see Fig. 3). The
experimental approach was also used to investigate size scale effects in the mechanical properties of ZnO
nanowires (Agrawal, et al., Nano Letters, 2008).
A
B
B
Fracture
C
C
5 nm
D
E
Figure 3: TEM image (A) of multiple-shell fracture. Paths B and C were used to create intensity profiles (B
and C) on either side of the fracture to verify that three shells broke. (D) Normalized force vs. strain for
each specimen. The irradiation dose (and thus the inter-shell cross-linking) increases with sample number.
The normalized force is applied load divided by the expected load on the outer shell given its diameter and
theoretical failure stress. (E) Stress-strain curves of all the MWNTs specimens (Peng et al., Nature
Nanotechnology, 2008).
The nanoscale material testing concepts developed by Espinosa and their derivatives have a direct and
significant impact on the electronic and sensor industries. They have greatly advanced the electromechanical characterization of nanoscale wires, tubes and fibers currently employed in the engineering of
next generation of composite materials, sensors, electronic memories and logical devices. They also enable
direct comparison between quantum/atomistic models and experiments in the quest for advancing
scientific knowledge, and the engineering of novel materials with unique properties and functionality (Peng
et al., Nature Nanotechnology, 2008). His inter-shell cross-linking work has a direct impact on the
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aerospace industry (Boeing, NASA) and their efforts to scale up in size carbon nanotube-based fiber
materials without loss in stiffness, strength and performance.
B
C
Electrochemical Deposition
Catalyst Arrays
CNT Growth
Parallel Deposition of Nanowires
Growth
1 um
Catalyst
Arrays of CNT-Based NEMS
Core Technology:
Volcano Tip
A
1 um
D
Protein Patterning and Single Cell Studies
Nanofountain
Probes
Fluorescent
Marker Injection
E
Direct Single Cell
Injection
Figure 4: (A) Nanfountain probes serve as the core enabling technology of a number of applications. (B)
Electrochemical deposition techniques for the NFP direct-write fabrication of large-scale arrays of
nanowires; (C) direct deposition of catalyst for CVD growth of carbon nanotube arrays for NEMS; (D)
electric-field-controlled protein patterning and substrate patterning for bio-detection and single cell
studies, and; (E) direct injection of single cells for nanomaterial-mediated drug delivery studies. The
injection is combined with fluorescence microscopy to investigate cytoskeleton dynamics.
Nanofountain Probes for Direct-Write Nanofabrication and Cell Studies
Espinosa and students pioneered the so-called Nanofountain Probe (NFP, Fig. 4A), an atomic force
microscopy probe capable of patterning of molecular “inks” in solution with sub-100-nanometer resolution.
These probes are unique in that they incorporate microfluidic elements (reservoir and microchannels) into
atomic force microscopy probes. The liquid ink is fed from on-chip reservoirs to apertured writing probes
via a series of enclosed microchannels. The sharp probes provide high resolution deposition (sub-100 nm)
while providing continuous fluid delivery. Among their unique capabilities, one can mention direct
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deposition of biomolecules (DNA, proteins), without tip functionalization, and the patterning of nano size
particles in suspension, something not achievable with regular AFM tips using dip pen nanolithography (a
technique developed by the Mirkin group). More recently, Espinosa and students leveraged the unique tip
geometry of the Nanofountain Probe to inject functional nanomaterials directly into live cells. This
demonstration opens the door to a host of new studies of nanomaterial-mediated drug delivery, cellular
pathway, and toxicity studies.
Three salient features of the technology are: i) its scalability to 1-D and 2-D arrays, ii) submicron resolution,
and iii) low tip wear when diamond is employed (see Kim et al., Small 2005). A 1-D array of nanofountain
probes with two reservoirs has already been developed and its capability of simultaneously patterning two
different molecular inks demonstrated by the Espinosa group (J. of Microengineering and Micromechanics,
2006). Note that scalability to full wafer manufacturing is a major advantage of the NFP over other
deposition technologies based on micro/nano pipettes and their derivatives. As such, this core technology
has the potential to impact a significant number of nanotechnologies, e.g., parallel electrochemical
deposition of nanowires (Fig. 4B), patterning of 2-D arrays of catalysts nanoparticles for wafer level
massively parallel fabrication of NEMS (Fig. 4C), protein patterning for cell adhesion, proliferation and
motility studies (Fig. 4D), and direct injection of cells with drugs and chemicals to investigate cell function
and associated diseases.
The nanofountain probe is being used for the manufacturing of DNA (Kim et al., Advanced Materials, 2007)
and protein chips (Loh et al., PNAS, 2008), a technology of great interest to the life science industry and
critical to identify biomarkers associated to specific diseases. Fig. 5 shows examples of proteins written
directly on a gold substrate using the nanofountain probe. In this case, an electric field applied between
the chip reservoir and substrate was used to assist transport of the charged proteins in buffer solution.
This affords an additional degree of control over protein deposition and enables extremely rapid patterning
(e.g., protein lines written at 80 microns/sec, see Figs. 5b,c). It is worth emphasizing that the integrated tipfluidic system can also be used to deliver, with high spatial resolution and minimal disruption, drugs and
other chemical compounds to the cytoskeleton of individual cells allowing novel studies in cell function and
associated diseases. This concept has recently been demonstrated by our group in laboratory in-vitro
experiments.
Figure 5: Examples of direct-write protein patterning using the NFP. (a) Dot array created with decreasing
dwell times. (b,c) Line arrays of protein deposited at a rate of 80 microns/sec.
The Nanofountain Probe is also being applied to the development of nanomaterial-mediated drug delivery
schemes (Loh, et al., Small, 2009), and cellular pathway and toxicity studies. The NFP enables these studies
at the single cell level through direct in vitro injection. This adds a critical degree of control to
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developmental experiments and enables a new level of comprehensive analysis. By selecting and injecting
a single cell within a population (rather than applying the same dose to the entire population), one can
now affect a response in the targeted cell and subsequently investigate cellular pathways or the
intercellular mobility of the injected material based on the response of neighboring cells. In recent work,
the NFP was successfully used to target and directly inject functional nanoparticles into live cells. This
enables study of, for example, new nanomaterial-mediated drug delivery schemes at a truly single cell
level. As an initial demonstration, fluorescently-tagged diamond nanoparticles (Figure 4E) were injected
into live cells and imaged. This method is currently being investigated for single cell dosing, toxicology, and
gene expression studies.
The potential of the nanfountain probe technology was highlighted by Dr. Arden L. Bement, Jr., Director of
the National Science Foundation in a lecture entitled "Partnerships at the Frontier" delivered at the
Accelerating Innovation Foundation Conference 2005, National Academies of Science, Washington, DC,
October 19, 2005. For more information see: http://www.nsf.gov/news/speeches/bement/05/alb051019_
innoforum.jsp. Dr. Bement stated: “Consider nanotechnology, the best candidate for next-generation
general-purpose technology. NSF's Nanoscale Science and Engineering Centers are among our newest, yet
are already producing results. The miniscule tip on an atomic-force microscope helps researchers both
"see" and manipulate the nanoscale environment. Now, engineers at the NSF-supported Nanoscale Science
and Engineering Center for Integrated Nanopatterning and Detection Technologies have substantially
improved this vital tool. They have created two novel technologies that enable such tips to write features
as small as viruses and to withstand abuse with the resilience of diamond. Eventually, vast arrays of such
nanofountain probes could be used for crafting complex semiconductors or intricate protein arrays.”
5 µm
500
nm
Figure 6: Slides from Dr. Arden L. Bement, Jr. presentation delivered at the Accelerating Innovation
Foundation Conference 2005, National Academies of Science, Washington, DC, October 19, 2005.
NEMS – Feedback-Controlled Carbon Nanotube-Based Switches
The Espinosa group is also contributing toward the development of nano-electro-mechanical systems
(NEMS), which are expected to play a major role in the next generation of electronic systems. Since the
invention of the integrated circuit (IC), the semiconductor industry has boomed following Moore’s law.
However, with the characteristic dimension achievable by various photolithography techniques
approaching their physical limits, scientists began searching for new materials and new device concepts.
The advantages of nanotube-based devices include high integration levels, high working frequency, and
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low energy consumption. A novel carbon nanotube-based nanoelectromechanical switch exhibiting
bistability (“on” and “off” states) based on feedback control of current tunneling was invented and its
operation demonstrated by the Espinosa group. The device is made of a freestanding multiwalled carbon
nanotube interacting electro-statically with an underlying electrode (Fig. 6). In the device circuit, there is a
resistor in series with the nanotube, which plays an important role in the functioning of the device by
adjusting the voltage at the tunneling junction, which develops when the CNT cantilever is pulled-in.
U
R
i
W/Pt
CNT or NW
Si3N4
SiO2
Si
Au
Figure 6: Schematic of feedback-controlled freestanding carbon
nanotube-based switch. The device consists of a carbon
nanotube fixed at one end to a top electrode and cantilevered
over a bottom electrode. For an applied voltage V>VPI (pull-in
voltage), the generated electrostatic force causes the CNT to
accelerate toward the bottom electrode. When the tip of the
CNT approaches the electrode, a tunneling current begins to
flow, signifying a closed circuit. This current in turn flows
through the resistor, causing a drop in the bias (and thus the
electrostatic force). In this way the resistor modulates the bias,
stabilizing the switch in the “ON” state.
Figure 7: Schematics of the setup for in-situ SEM testing of nanotube cantilever devices. Experimentally
measured and theoretically predicted I–U characteristic curves (Ke et al., APL, 2004, Small, 2006].
Theoretical analysis (Ke et al., APL 2005 and JMPS, 2006) and in-situ SEM device level testing (Small, 2006)
were performed to confirm bi-stability as manifested by a voltage hysteresis between pull-in and pull-out
events (see Fig. 7). Because of the potential of carbon nanotubes as building blocks for electronics devices
and sensors, many leading research groups in the world have demonstrated devices with various
capabilities. For instance, the Lieber’s group at Harvard University reported the first nanotube based nonvolatile memory elements in 2000. The McEuen’ group at Cornell University designed and demonstrated a
nanotube based tunable oscillators in 2004. The Kinaret’s group at Chalmers University of Technology in
Sweden reported nanotube based nano-relays in 2003. However, transition of the technology to industry
has been complicated by challenges associated to device manufacturing and reliability. The bistable
tunneling switch developed by Espinosa may offer some advantages in this respect: i) it tolerates significant
variability in the distance between freestanding one-dimensional nanostructure and bottom electrode; ii) it
is compatible with current MEMS fabrication techniques and ii) it is scalable to 2-D arrays. Potential
applications of the device include NEMS switches, random-access memory elements, and logic devices.
Sensing applications are also envisioned.
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b
a
20 cm
d
2’
2
n
t2
t1
1’
1
3’
3
e
c
g
f
z
y
x
x
h
Core
Overlap
Core
Figure 8 Left: (a) Inside view of red abalone shell (b) Cross section of the shell. (c) Crack resistance (JR)
curves for nacre from two experiments. (d) Prior to crack advance a tablet sliding zone develops ahead of
the crack tip. (e) As the crack advances it leaves a wake of inelastically deformed material (d and e: optical
images; red arrow shows location of crack tip at the onset of crack propagation and the steady state
regime). (f) Schematic showing the J contour used in our modeling. (g) Crack deflection and debonding of
tablets along a crack. (h) Tablet sliding on one another (g and h: scanning electron micrographs). Right: 3-D
microstructural modeling.
Mechanics of Biomaterials
Mother-of-pearl, also known as nacre, is the iridescent material which forms the inner layer of seashells
from gastropods and bivalves. It is mostly made of microscopic ceramic tablets densely packed and bonded
together by a thin layer of biopolymer (Fig. 8). The hierarchical microstructure of this biological material is
the result of millions of years of evolution, and it is so well organized that its strength and toughness are
far superior to the ceramic it is made of. To understand the mechanisms responsible for such outstanding
performance, we performed a multiscale experimental study over several length scales using TEM, SEM,
AFM, nanoindentation, and a microtesters (Barthelat et al., JMPS, 2007). Our work revealed that the
inelastic mechanism responsible for this behavior is sliding of the tablets on one another accompanied by
10
transverse expansion in the direction perpendicular to the tablet planes. Such mechanism was found to be
the result of tablet waviness and the unique properties of the biopolymer present at the interfaces. Three
dimensional representative volume elements, incorporating cohesive elements with a constitutive
response consistent with the interface material and nanoscale features, were numerically analyzed (Fig. 8).
The simulations revealed that even in the absence of nanoscale hardening mechanism at the interfaces,
the microscale waviness of the tablets could generate strain hardening, thereby spreading the inelastic
deformation and suppressing damage localization leading to material instability. Fracture studies made
evident that the formation of large regions of inelastic deformations around cracks, with a very well
developed wake, is the main contribution to its toughness (Barthelat and Espinosa, Exp. Mech., 2007). In
addition, it was shown that tablet junctions (vertical junctions between tablets) strengthen the
microstructure but do not contribute to the overall material hardening (Tang et al., JMPS, 2007). Statistical
variations within the microstructure were found to be beneficial to hardening and to the overall
mechanical stability of nacre but not essential to its performance. These results provide new insights into
the microstructural features that make nacre tough and damage tolerant. Based on these findings, design
guidelines for composites mimicking nacre were proposed (Barthelat et al., JMPS, 2007). Our group is
currently pursuing rapid prototyping and microfabrication strategies to make a synthetic material
exhibiting the unique properties of seashells.
Dynamic Failure of Materials and Scaled Structures
Espinosa has also made significant contributions in the area of dynamic failure of materials by developing a
number of wave propagation experimental techniques and interpreting those using advanced
computational mechanics models. The experiments include pressure-shear plate impact with specimen
recovery, dynamic torsion of nanocrystalline ceramic coatings using digital image correlation and high
speed photography (Society of Experimental Mechanics best paper award for digital image correlation
measurements at high rates of deformation), high temperature spallation of metals, dynamic friction using
a Kolsky bar, and dynamic collapse of cellular materials. More recently a highly instrumented wave
propagation experiment was developed to investigate fluid-structure interaction (FSI) under blast loading
(Fig. 9). The design is based on scaling laws to achieve a laboratory scale apparatus that can capture
essential features in the deformation and failure of large scale naval structures. In the FSI setup, a water
chamber made of a steel tube is incorporated into a gas gun apparatus. A scaled structure is fixed at one
end of the steel tube and a water piston seals the other end. A flyer plate impacts a water piston and
produces an exponentially-decaying pressure history in lieu of explosive detonation. The pressure induced
by the flyer plate propagates and imposes an impulse to the structure (panel specimen), which response
elicits bubble formation and water cavitations. Calibration experiments and numerical simulations proved
the experimental setup to be functional (Lee et al., Exp. Mech., 2007). The experimental diagnostic
included measurements of flyer impact velocity, pressure wave history in the water and full deformation
fields by means of shadow Moiré and high speed photography. Using these measurements, a one-to-one
comparison with model predictions was achieved. Furthermore, performance improvements resulting
from optimized stainless steel sandwich panels, of the same mass per unit area as solid panels, was
assessed. The study showed that for a range of applied impulses, up to a 50% reduction in maximum panel
deflections can be obtained when crushable cores are employed (Mori et al., J. Mech. Mat. and Structures,
2008).
The Espinosa group also developed custom software accounting for multi-body finite kinematics contact,
finite deformation plasticity, temperature effects, fragmentation and comminution. An example is the
development of ceramic models based on grain level representative volume elements (RVE) of ceramic
microstructures (Fig. 10). The model was employed to interpret both normal impact soft-recovery and
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pressure-shear soft recovery experimental results. The numerical simulations were based on a 2-D
stochastic finite element analysis. Normal plate impact velocity histories obtained in earlier studies were
used to assess conditions under which the cohesive fracture model could capture failure mechanisms
experimentally observed. The analyses showed that in order to properly model damage kinetics a
stochastic distribution of grain boundary strength and detailed modeling of grain morphology are required
(Zavattieri and Espinosa, Acta Mat., 2001). Moreover, it was determined that compressive wave
attenuation at stress levels below the Hugoniot elastic limit, a counterintuitive finding that preoccupied the
ceramic community in the early 90’s, was the result of grain boundary relaxation in shear due to the
presence of a glassy phase. In these simulations, compression-shear properties independently identified for
glass were employed in the cohesive law describing the grain boundary constitutive law. Overall
compression wave decay and nucleation of microcracks at triple grain junctions naturally emerged from
the simulations. These studies were significant because the simulations were compared to experimental
data containing information on crack initiation and kinetics as observed in plate impact velocity histories
and electron microscopy studies performed on recovered samples.
Figure 9: FSI experimental set up, deformed stainless steel sandwich panel with honeycomb core, and
series of shadow Moiré images acquired in real time with high speed photography.
Figure 10: (a) Schematics of microcracking at grain boundaries using an irreversible interface cohesive law.
(b) Application to fragmentation and pulverization.
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Some of the Espinosa group early research work focused on continuum-discrete models for the high-strain
rate response of advanced materials (including brittle and composite materials). This included the
development and implementation of models and numerical algorithms in finite deformation FEM codes
using parallel programming. The models included: i) Adaptive remeshing techniques based on the
optimization of element size and shape (including refinement and coarsening) with mapping of state
variables within a finite deformation framework (Fig. 11a), ii) Continuum/Discrete models, based on
fracture and damage models together with a multibody contact-interface methodology to capture crack
initiation, growth, coalescence and interaction between fragments (Fig. 11b), and iii) the combination of
both, adaptive remeshing and the continuum/discrete model to capture delamination and fracture in fiber
reinforced laminate composites (Fig. 11c).
Figure 11: Computational techniques for mesoscopic modeling of failure: (a) Examples of adaptive
remeshing technique based on optimization of element size and shape according to local material
behavior. Examples include impact problems of rod penetration, high-speed machining and ballistic
penetration. (b) Continuum/discrete models for fragmentation in brittle materials, (c) Combination of (a)
and (b) for delamination of glass reinforced composites under ballistic impact.
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PUBLICATIONS: (selected publications listed by topic)
1. H.D. Espinosa, B.C. Prorok, and M. Fischer, “A Methodology for Determining Mechanical
Properties of Freestanding Thin Films and MEMS Materials,” Journal of the Mechanics and
Physics of Solids, Vol. 51, pp. 47-67, 2003 (among the most cited papers in mechanical
characterization of MEMS materials); H.D. Espinosa, B.C. Prorok and B. Peng, "Plasticity Size
Effects in Freestanding Submicron Polycrystalline FCC Films Subjected to Pure Tension,"
Journal of the Mechanics and Physics of Solids, Vol. 52, p. 667–689, 2004.
The effect of film thickness on tensile strength and hardening rate, in the absence of strain gradients,
was first characterized by means of a novel membrane deflection experiment (using a nanoindenter
as a loading device and microfabrication to make freestanding submicron specimens). This work
was first published in three conference proceeding in 2001, SEM June 2001, MRS Fall 2001,
ASME Interpack’01 and later in JMPS, in 2003. While size scale plasticity in thin films was
previously demonstrated by means of wafer curvature measurements or cantilever bending
experiments, this work is unique in several respects: a) the tests were performed in pure tension
(absence of loading gradients); b) they were performed in submicron freestanding films (no
interfaces that can pile up dislocations); c) the test was instrumented with a Mirau microscope such
that film deformation, localization and fracture were observed and correlated to stress-strain
behavior in real time. The test was later extended to measure fracture toughness in thin films (Bei
and Espinosa, JMEMS, Vol. 14, p. 153, 2005) and to identify properties of nanomaterials, e.g.,
applicability of Weibull theory to nanocrystalline diamond, amorphous diamond, and single crystal
SiC films (JAP, Vol. 94, No. 9, p. 6076, 2005; APL, Vol. 89, No. 7, p. 73111, 2006; JMR, Vol. 22,
No. 4, 2007).
2. H.D. Espinosa, S. Berbenni, M. Panico and K.W. Schwarz. "An interpretation of Size Scale
Plasticity in Geometrically Confined Systems," Proceedings of the National Academy of
Sciences of the USA, 102 (47): 16933-16938 November 22, 2005. In this article a discrete
dislocation dynamics model is formulated and employed in the interpretation of the
experimentally observed size scale plasticity in freestanding metallic thin films. H. Tang, K.
Schwarz and H.D. Espinosa. "Dislocation Escape-Related Size Effects in Single-Crystal
Micropillars under Uniaxial Compression," Acta Materialia, Vol. 55, No. 5, p. 1607-1616,
2007. This article derives size scaling laws, which are then verified by means of 3-D discrete
dislocation dynamics simulations. H. Tang, K.W. Schwarz, and H.D. Espinosa, “DislocationSource Shutdown and the Plastic Behavior of Single-Crystal Micropillars,” Physical Review
Letters, Vol. 100, No. 18, 2008.
3. Y. Zhu and H.D. Espinosa. " An electromechanical material testing system for in situ electron
microscopy and applications " Proceedings of the National Academy of Sciences of the USA,
Vol. 102, pp. 14503-14508, 2005. H.D. Espinosa, Y. Zhu and N. Moldovan. "Design and
operation of a MEMS-based material testing system for nanomechanical characterization,"
Journal of Microelectromechanical Systems, Vol. 16, No. 5, 1219, 2007.
This article reports the integration of electronic actuation and sensing in a single MEM system
providing a complete nano scale testing apparatus. Load is measured electronically, with resolution
14
of about 10 nano-Newtons, based on differential capacitive sensing while loading under
displacement control is achieved by means of thermal actuation. When the system is placed in a
transmission electron microscope (TEM), high resolution atomic images of the specimen can be
obtained in real time without the need for shifting the electron beam. The implication is that a
number of nanostructures, with characteristic dimensions smaller than 100 nm, can be tested and
failure modes at the atomic level identified. To put this in perspective, note that other
microfabricated devices for in-situ testing, previously reported in the literature, are not true MEMS
in the sense that they do not couple mechanical and electronic fields to accomplish loading and its
measurement. For instance, microfabricated loading frames are based only on mechanical
deformation. They do not posses independent electronic measurement of load and load application
is not integrated into one micro device. This has several implications with the most significant being
the requirement of having to move and/or change the magnification of the electron beam to
determine load. As a result, simultaneous observation of atomic defects and load measurement are
not possible. As the popularity of nanoscale mechanical characterization of materials increases, the
superiority of the m-MTS will become pervasive. The micro-MTS concept is applicable to the
characterization of mechanical, thermal and electro-mechanical properties not only of metallic
nanowires and carbon nanotubes but also of a large number of organic and inorganic nanomaterials.
4. B. Peng, M. Locascio, P. Zapol, S. Li, S.L. Mielke, G.C. Schatz, and H.D. Espinosa,
“Measurements of near-ultimate strength for multiwalled carbon nanotubes and irradiationinduced crosslinking improvements,” Nature Nanotechnology, Vol. 3, No. 10, p. 626-631, 2008.
Commentary by Eric Stach, "Nanotubes reveal their true strength," Nature Nanotechnology,
Vol. 3, No. 10, p. 586-587, 2008. M. Locascio, B. Peng, P. Zapol, Y. Zhu, S. Li, T. Belytschko,
and H.D. Espinosa, "Tailoring the Load Carrying Capacity of MWCNTs Through Inter-shell
Atomic Bridging," Experimental Mechanics, Vol. 49, No. 2, p. 169-182, 2009.
Using the m-MTS in-situ a TEM, Espinosa and students demonstrated that the number of shells
failing in a multi-walled CNT is a function of initial atomic structure and electron/ion radiation. The
reason for this phenomenon is that inter-shell cross-linking occurs during growth or during
specimen radiation with electrons or ions possessing energy above a certain threshold (energy for
vacancy formation in the carbon shell). While cross-linking was hypothesized prior to this work,
there was no direct imaging of atomic structure or correlation to measurements of associated loaddisplacement curves (see figure and table below). An important implication of this work is that the
commonly used assumption of outer shell failure in MWCNTs may lead to wrong calculations of
stress and modulus. Even for experiments conducted in-situ an scanning electron microscope, in
which the electron energy is below the vacancy formation energy, there is evidence that the outershell failure hypothesis may be inaccurate (A.H. Barber et al., Comp. Science and Tech., Vol. 65,
2005, p. 2380). The evidence is indirect and results from discrepancies between experimentally
determined failure stress and Young’s modulus and ab initio or DFT quantum mechanical
predictions for the same properties
5. R. Agrawal, B. Peng and H.D. Espinosa, "Experimental-Computational Investigation of ZnO
Nanowires Strength and Fracture" Nano Letters, Volume 9, No 12, p 4177-4183, 2009.R.
Agrawal, B. Peng, E. Gdoutos, and H. D. Espinosa, “Elasticity Size Effects in ZnO Nanowires –
A Combined Experimental-Computational Approach”, Nano Letters, Vol. 8, No. 11, p. 3668-
15
3674, 2008. H.S. Park, W. Cai, H.D. Espinosa, and H. Huang, "Mechanics of Crystalline
Nanowires," MRS Bulletin, Vol. 34, No. 3, p. 178-183, 2009.
6. K.-H. Kim, N. Moldovan, and H.D. Espinosa, "A Nanofountain Probe with Sub-100 nm
Molecular Writing Resolution," Small, Vol. 1, No. 6, pp. 632-635, 2005. N. Moldovan, K-H.
Kim, and H.D. Espinosa. "Multi-Ink Linear Array of Nanofountain Probes." Journal of
Micromechanics and Microengineering, Vol. 16, No. 10, p. 1935-1942, 2006. (posted in IoP
Select, a special collection of journal articles, chosen by IoP Editors based on one or more of the
following criteria: Substantial advances or significant breakthroughs; A high degree of novelty;
Significant impact on future research.)
7. B. Wu, A. Ho, N. Moldovan, and H.D. Espinosa. “Direct Deposition and Assembly of Gold
Colloidal Particles Using a Nanofountain Probe”, Langmuir, Vol. 23, No. 17, 2007. O. Loh, A.
Ho, J. Rim, P. Kohli, N. Patankar, H. Espinosa, “Electric Field-Induced Direct Delivery of
Proteins by a Nanofountain Probe,” Proceedings of the National Academy of Sciences, Vol. 105,
No. 43, p. 16438-16443, 2008. O. Loh, R. Lam, M. Chen, N. Moldovan, H. Huang, D. Ho, and
H.D. Espinosa, "Nanofountain-Probe-Based High-Resolution Patterning and Single-Cell
Injection of Functionalized Nanodiamonds," Small, Vol. 5, No. 14, p. 1667-1674, 2009 (Cover
Article).
8. K.-H. Kim, N. Moldovan, C. Ke, H.D. Espinosa, X. Xiao, J.A. Carlisle, and O. Auciello. "Novel
Ultrananocrystalline Diamond Probes for High- Resolution Low-Wear Nanolithographic
Techniques," Small, Vol. 1, No. 8-9, p. 866-874, 2005. R. Agrawal, N. Moldovan and H.D.
Espinosa, "An Energy-based Model to Predict Wear in Nanocrystalline Diamond Atomic Force
Microscopy Tips" Journal of Applied Physics, Volume 106, 064311, 2009.
9. C.-H. Ke and H.D. Espinosa, "Feedback Controlled Nanocantilever Device," Applied Physics
Letters, Vol. 85, p. 681-683, 2004. C.-H. Ke and H.D. Espinosa. "In situ Electron Microscopy
Electromechanical Characterization of a Bistable NEMS Device," Small, Vol. 2, No. 12, p.
1484-1489, 2006. C.-H. Ke, N. Pugno, B. Peng and H.D. Espinosa, "Experiments and Modeling
of Nanotube NEMS Devices," Journal of the Mechanics and Physics of Solids,Vol.53, pp.13141333, 2005.
10. F. Barthelat, H. Tang, P.D. Zavattieri, C.-M. Li, H.D. Espinosa. "On the mechanics of motherof-pearl: A key feature in the material hierarchical structure," Journal of the Mechanics and
Physics of Solids, Vol. 55, No. 2, p. 306-337, 2007. F. Barthelat and H.D. Espinosa, “An
Experimental Investigation of Deformation and Fracture of Nacre - Mother of Pearl”,
Experimental Mechanics, Vol. 47, No. 3, 2007. H.D. Espinosa, J.E.Rim, F. Barthelat, and M.J.
Buehler, "Merger of Structure and Material in Nacre and Bone - Perspectives on de novo
Biomimetic Materials" Progress in Materials Science, DOI: 10.1016/j.pmatsci.2009.05.001,
2009.
11. P.D. Zavattieri and H.D. Espinosa, “Grain Level Analysis of Crack Initiation and Propagation in
Brittle Materials,” Acta Materialia, Vol. 49, No. 20, p. 4291-4311, 2001. P.D. Zavattieri and
H.D. Espinosa, "An Examination of the Competition between Bulk Behavior and Interfacial
16
Behavior of Ceramics Subjected to Dynamic Pressure-Shear Loading," Journal of the
Mechanics and Physics of Solids, Vol. 51, No. 4, p. 607-635, 2003. H.D. Espinosa and B.A.
Gailly, “Modeling of Shear Instabilities Observed in Cylinder Collapse Experiments Performed
on Ceramic Powders,” Acta Materialia, Vol. 49, No. 19, p. 4135-4147, 2001. H.D. Espinosa,
P.D. Zavattieri, and S. Dwivedi, “A Finite Deformation Continuum/Discrete Model for the
Description of Fragmentation and Damage in Brittle Materials,” special issue of Journal of the
Mechanics and Physics of Solids, Vol. 46, No. 10, p. 1909-1942, 1998.
12. H.D. Espinosa, F. Barthelat, Z. Wu, and B.C. Prorok, “An Experimental Methodology for the
Investigation of Failure Mechanisms in Nanocrystalline Coatings Subjected to Dynamic
Torsion,” Experimental Mechanics, Vol. 43, No. 3, pp. 331-340, 2002 (SEM 2005 Hetenyi Best
Paper Award).
13. H.D. Espinosa and S. Nemat-Nasser, “Low-Velocity Impact Testing,” ASM Handbook, Vol. 8,
p. 539-559, 2000. H.D. Espinosa and R.J. Clifton, “Special Issue on Advances in Failure
Mechanisms in Brittle Materials,” Mechanics of Materials, edited by H.D. Espinosa and R.J.
Clifton, Vol. 29, No. 3-4, p. 141-142, 1998.
14. S. Lee, F. Barthelat, J.W. Hutchinson, and H.D. Espinosa. "Dynamic failure of metallic
pyramidal truss core materials - Experiments and modeling." International Journal of Plasticity,
Vol. 22, No. 11, p. 2118-2145, 2006; H.D. Espinosa, S. Lee, and N. Moldovan. "A Novel Fluid
Structure Interaction Experiment to Investigate Deformation of Structural Elements Subjected to
Impulsive Loading." Experimental Mechanics, Vol. 46, No. 6, p. 805-824, 2006. L.F. Mori, D.T.
Queheillalt, H.N.G. Wadley and H.D. Espinosa, "Deformation and Failure Modes of I-Core
Sandwich Structures Subjected to Underwater Impulsive Loads," Experimental Mechanics, Vol.
49, No. 2, p. 257-275, 2009.
PATENTS: (List no more than 15 in approximate order of significance and comment on the most
important up to a maximum of 5. As with the publications, please cite those patents, which
specifically support the nominee's achievements and establish a claim to the honor for which the
individual is nominated. In the event that the nominee holds no patents, please so indicate.)
1) U.S. Patent #7,250,139
Issued: July 31, 2007
Title: Nanotipped device and method
Inventors: Horacio Espinosa, Nicolaie Moldovan, Keun-Ho Kim
Assignee: Northwestern University (Evanston, IL)
Application No.: 10/801,928
Filed: March 16, 2004
Claims benefits and priority of: Provisional application No. 60/455,898 filed Mar. 19, 2003.
Abstract
A dispensing device has a cantilever comprising a plurality of thin films arranged relative to one
another to define a microchannel in the cantilever and to define at least portions of a dispensing
microtip proximate an end of the cantilever and communicated to the microchannel to receive
17
material therefrom. The microchannel is communicated to a reservoir that supplies material to the
microchannel. One or more reservoir-fed cantilevers may be formed on a semiconductor chip
substrate. A sealing layer preferably is disposed on one of the first and second thin films and
overlies outermost edges of the first and second thin films to seal the outermost edges against
material leakage. Each cantilever includes an actuator, such as for example a piezoelectric actuator,
to impart bending motion thereto. The microtip includes a pointed pyramidal or conical shaped
microtip body and an annular shell spaced about the pointed microtip body to define a materialdispensing annulus thereabout. The working microtip may be used to dispense material onto a
substrate, to probe a surface in scanning probe microscopy, to apply an electrical stimulus or record
an electrical response on a surface in the presence of a local environment created around the tip by
the material dispensed from the tip or to achieve other functions.
2) U.S. Patent Application (Proprietary)
Continuation-in-Part application to 10/801,928
Title: Microchannel Forming Method and Nanotipped Dispensing Device Having a
Microchannel
Inventors: Horacio Espinosa, Nicolaie Moldovan
Application No.: 11/516,039
Filed: September 5, 2006
No provisional patent application filed
Northwestern Identification No.: NU 25074
Abstract
A method of forming a microchannel as well as a thin film structure including same is made by
forming a first thin film on a side of a substrate, forming a fugitive second thin film on the first
thin film such that the second thin film defines a precursor of the elongated microchannel and a
plurality of extensions connected to and extending transversely relative to the precursor along a
length thereof a third thin film is formed on the first thin film and the fugitive second thin film such
that the second thin film resides between the first thin film and the third thin film. A respective
access site is formed in a region of the third thin film residing on a respective extension and
penetrating to the fugitive second thin film. The fugitive second thin film forming the precursor is
selectively removed from between the first thin film and the third thin film using an etching medium
introduced through the access sites, thereby forming the microchannel between the first thin film
and the third thin film. The method preferably further includes forming a sealing layer on the third
thin film in a manner to close off open access sites remaining after selective removal of the second
thin film.
3) U.S. Patent 7612424
Issued: Nov. 3, 2009
Title: Nanoelectromechanical Bistable Cantilever Device
Inventors: Horacio Espinosa, Changhong Ke
Application No.: 11/385,970
Filed: March 21, 2006
Northwestern Identification No.: NU 24054/25071
18
Abstract
Nano-electromechanical device having an electrically conductive nano-cantilever wherein the nanocantilever has a free end that is movable relative to an electrically conductive substrate such as an
electrode of a circuit. The circuit includes a power source connected to the electrode and to the
nano-cantilever for providing a pull-in or pull-out voltage there between to effect bending
movement of the nano-cantilever relative to the electrode. Feedback control is provided for varying
the voltage between the electrode and the nano-cantilever in response to the position of the
cantilever relative to the electrode. The device provides two stable positions of the nano-cantilever
and a hysteresis loop in the current-voltage space between the pull-in voltage and the pull-out
voltage. A first stable position of the nano-cantilever is provided at sub-nanometer gap between the
free end of the nano-cantilever and the electrode with a pull-in voltage applied and with a stable
tunneling electrical current present in the circuit. A second stable position of the nano-cantilever is
provided with a pull-out voltage between the cantilever and the electrode with little or no tunneling
electrical current present in the circuit. The nano-electromechanical device can be used in a
scanning probe microscope, ultrasonic wave detection sensor, NEMS switch, random access
memory element, gap sensor, logic device, and a bio-sensor when the nano-cantilever is
functionalized with biomolecules that interact with species present in the ambient environment be
them in air or aqueous solutions. In the latest case, the NEMS needs to be integrated with a
microfluidic system.
4) U.S. Provisional Patent Application (Proprietary)
Title: Artificial Composite Mimicking Nacre
Inventors: Horacio Espinosa, Francois Barthelat
USSN: 60/858,577, Pending
Filed: 13 Nov 2006
Northwestern Identification No. 26164
Abstract
The present invention refers to a novel composite design with enhanced toughness, which
incorporates features mimicked from nacre (mother of pearl). Ceramic materials have many
attractive engineering qualities such as stiffness, hardness, wear resistance, and resistance to high
temperatures. The main obstacle to a wider use of ceramics in engineering applications is their
brittleness: they fail at very small deformations and in a catastrophic fashion, and they are fragile in
tension. The composite material proposed here is made of 95% or more of a brittle material, yet it is
capable of deformation strains in excess of 10%. In addition, the design is such that rather than
failing at one location, damage is distributed over large volumes of material. This makes the
material better at resisting, and even stopping cracks. This material retains the properties that make
ceramics attractive, but it is at least 10 times tougher. Such material will become very attractive for
a variety of applications ranging from armor to electronic substrates.
19
5) U.S. Provisional Patent Application (Proprietary)
Title: Four-terminal Electromechanical Characterization in-situ TEM
Inventors: Horacio Espinosa and Rodrigo Bernal
USSN: Provisional Patent Application No. 61/279,833
Filed: 3 Nov 2009
Northwestern Identification No. 29155
Housed in a Transmission Electron Microscope (TEM), the invention characterizes mechanical and
electrical properties of individual nanostructures such as a nanowire or nanotube in a four-terminalKelvin setup. Its in-situ capabilities mean that atomic resolution imaging and mechanical/electrical
characterization can be performed simultaneously in real-time. By eliminating any influence of
electrode interfaces, the MEMS-based Four-terminal Kelvin setup is able to provide true
characterization of electrical properties. Coupled with uniaxial mechanical testing, the invention
provides unprecedented capabilities to test nanostructures both mechanically and electrically.
Mechanical tests are performed in tension. Specimen ends are secured to movable shuttles. One
shuttle is rigidly connected to a thermal actuator, which imposes a controlled displacement to strain
the specimen; the remaining shuttle connects to a load sensor with nanoNewton resolution. A
window underneath the specimen enables specimen observation in the TEM.
6) U.S. Patent Application (Proprietary)
Title: Diamond Probes and Method of Making
Inventors: Horacio Espinosa, Nicolaie Moldovan
Application No.: 11/492,710
Filed: July 25, 2006
Claims benefits and priority of: Provisional application No. 60/702,544 filed July 26, 2005
Northwestern Identification No.: NU 24098/25075
Abstract
A probe for an atomic force microscope (AFM) and other uses includes an elongated cantilever
extending from a base wherein the cantilever includes an integral probe nano-size tip and wherein
the probe tip comprises wear resistant diamond. The cantilever can include a base on which a
metallic or other body is deposited to form a handling chip of the probe. An electrically insulating
layer or shell can be provided on the cantilever and probe tip with the exception of proximate an
apex of the probe tip.
20
BRIEF BIOGRAPHY: (Give birth date and place, citizenship, education, positions held, honors,
ASME activities, and participation in other engineering societies. In listing positions held, include
directorships of civic activities and industrial corporations. For a nominee having many honors, those
honors should be included that support the achievements for which the individual is being nominated.)
Horacio D. Espinosa received in 1981 his degree in Civil Engineering (6 years curriculum) from the
Northeast National University, Argentina. From 1981 to 1985 he worked as a structural engineer
and served as consultant for the “State Housing and Urban Development, Resistencia City,”
Argentina. In August of 1985 he started graduate studies at the Polytechnic of Milan, Italy and in
1987 he obtained a M.Sc. in Structural Engineering under the mentoring of Professor Giulio Maier.
In 1987 he began graduate studies at Brown University. In 1989 and 1990 he completed M.Sc.
degrees in Solid Mechanics and Applied Mathematics, respectively. In May of 1992, he completed
his Ph.D. in Applied Mechanics at Brown University under the supervision of Professors Rodney
Clifton and Michael Ortiz. He subsequently joined the Purdue University faculty as Assistant
Professor in the Department of Aeronautics and Astronautics and was promoted to Associate
Professor with tenure in 1997. During the 1998-1999 academic year he pursued a sabbatical leave
at Harvard University hosted by Professor John Hutchinson. In January of 2000 he joined the
Department of Mechanical Engineering at Northwestern University where he is currently the
James and Nancy Farley Chaired Professor. He has made contributions in the areas of dynamic
failure of advanced materials, computational modeling of fracture and delamination, and
experiments in micro- and nano-systems. He has published over 180 technical papers in these
fields. Professor Espinosa has received numerous awards and honors recognizing his research and
teaching efforts, including two Young Investigator Awards, NSF-Career and ONR-YIP, the American
Academy of Mechanics (AAM) 2002-Junior Award, the Society for Experimental Mechanics (SEM)
2005 HETENYI Award (Best Paper of the Year Award), the Society of Engineering Science (SES)
2007 Junior Medal, and the 2008 LAZAN award from SEM. He is also a member of the European
Academy of Sciences and Arts, and Fellow of AAM, ASME and SEM. He currently serves as Editorin-chief of the Journal of Experimental Mechanics, co-editor of the Wiley Book Series in Micro and
Nanotechnologies, and Associate Editor of the Journal of Applied Mechanics. From 1998 to 2004,
he served as editor of Mechanics, a publication of the American Academy of Mechanics. His
current research interests are on biomimetics, size scale plasticity, fracture and electromechanical coupling in 1-D nanostructures, NEMS, in-situ electron, Raman, and atomic probe
microscopy testing of nanostructures, and the development of microdevices for massively parallel
atomic probe nanofabrication of next generation of electronic circuits and bio-chips.
21
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