Abstract: This paper presents a high sensitivity micro capacitive tactile sensor that can detect normal
forces which is fabricated using deep reactive ion etching (DRIE) bulk silicon micromachining. The
tactile sensor consists of a force transmission plate, a symmetric suspension system, and comb
electrodes. The sensing character is based on the changes of capacitance between coplanar sense
electrodes and it can reach the aim of large sensing range. High sensitivity is achieved by using the
high aspect ratio comb electrodes with narrow comb gaps and large overlap areas. In this paper, the
sensor structure is designed, the capacitance variation of the proposed device is analyzed, and the
finite element analysis of mechanical behavior of the structures is performed.
Abstract: In this paper, the mechanical properties, such as the axial and radial Young’s moduli, shear
moduli, buckling loads and natural frequencies, of single-walled carbon nanotubes, are estimated by a
finite element approach. Each carbon nanotube is simulated as a frame-like structure and the primary
bonds between two nearest-neighboring atoms are treated as isotropic beam members with a uniform
circular cross-section. In the modeling work, the BEAM4 element in commercial code ANSYS is
selected to simulate the carbon bonds and the atoms are nodes. As to the input parameters of the
BEAM4 element, they are determined via the concept of energy equivalence between molecular
dynamics and structural mechanics, and represented in terms of the force constants of the carbon
bonds found in molecular mechanics. Based on this modeling concept, finite element models of both
armchair and zigzag types of carbon nanotubes with different sizes are established and the mechanical
properties of these tubes are then effectively predicted. Most of the computed results which can be
compared with existing results show good agreement. Moreover, the effects of tube diameter, length
etc., on the mechanical properties are also investigated.
Abstract: In recent years with the development of MEMS and NEMS, various micro and nano scale
experiments are required. In general, the smaller the sample, the smaller the force is in the
measurement. But it is difficult to load and measure such small force. We developed a probe-type
loading and force sensor system to measure micro/nano samples. The system employs a
semiconductor strain gauge of a cantilever type sensor and a micro manipulator. A highly sensitive,
stable sensing cantilever beam made of single crystal silicon is ion implanted to form the P-type
resistor (strain sensor). A tungsten probe with 100 nm radius of curvature was attached to the end of
the cantilever as the micro loading tip. We constructed the measurement system and investigated its
properties, such as linearity, dynamic response and stability. We also employed microspeckle
interferometry to calibrate the force sensor. In preliminary experiments, we successfully obtained the
force resolution 0.7 μN and applied our probe-type microforce sensor to calibrate an atomic force
microscope (AFM) probe beam and test a single silkworm filament.
Abstract: A modified model of simply supported ultrathin film for incorporating the surface effects
and geometrically nonlinear conditions is proposed on basis of Kirchhoff’s hypothesis. The
governing equations and non-classical boundary conditions are derived via using Hamilton’s
principle. The residual membrane force and bending moment, in which the contributions of surface
stresses and nonlinear terms are taken into account, are explicitly expatiated. Comparison between
the modified model and conventional plate theory is also given. Using the simply supported
bending strip-like film as an example, results indicate that the mechanical behaviors of the film are
size-dependent when the thickness of the film is nanometer.
Abstract: We examine the mobility of an edge dislocation pair on the shuffle plane in Si using
action-derived molecular dynamics (ADMD). ADMD is one of the specially designed schemes for
finding out the reaction pathways passing through transition states in the landscape of potential energy
surfaces. Via ADMD calculations, the various structural changes of dislocation line with atomic
resolution and their corresponding energy barriers are evaluated during the dislocation motion. The
energy barrier for the movement of an edge dislocation pair on shuffle plane is about 0.24 eV. In this
case, one bond between the atoms at the dislocation line is broken first, and then a new bond is formed
with the neighboring atom. The movement of the dislocation line is achieved by a sequence of making
new bond after bond-breaking of concerned atoms, which occur layer by layer. When the dislocation
moves through this mechanism, energy barrier for the dislocation movement does not depend on the
length of dislocation line. Thus the present result enables one to surmount the inherent limitation of
Peierls-Nabarro’s two-dimensional continuum model, which may fail to describe successfully
dislocation motion on the atomistic level.
Abstract: The stress induced in a workpiece under nanocutting are analyzed by an atomic-scale
model approach that is based on the energy minimization. Certain aspects of the deformation
evolution during the process of nanocutting are addressed. This method needs less computational
efforts than traditional molecular dynamics (MD) calculations. The simulation results demonstrate
that the microscopic cutting deformation mechanism in the nanocutting process can be regarded as
the instability of the crystalline structure in our atomistic simulations and the surface quality of the
finished workpiece varies with the cutting depth.
Abstract: This paper will discuss two different techniques to measure mechanical properties of thin
film, bulge test and nano-indentation test. In the bulge test, uniform pressure applies to one side of
thin film. Measurement of the membrane deflection as a function of the applied pressure allows one to
determine the mechanical properties such as the elastic modulus and the residual stress.
Nano-indentation measurements are accomplished by pushing the indenter tip into a sample and then
withdrawing it, recording the force required as a function of position. . In this study, modified King’s
model can be used to estimate the mechanical properties of the thin film in order to avoid the effect of
substrates. Both techniques can be used to determine Young’s modulus or Poisson’s ratio, but in both
cases knowledge of the other variables is needed. However, the mathematical relationship between
the modulus and Poisson's ratio is different for the two experimental techniques. Hence, achieving
agreement between the techniques means that the modulus and Poisson’s ratio and Young’s modulus
of thin films can be determined with no a priori knowledge of either.
Abstract: There are two kinds of microsprings often used: box microsprings and zig-zag (serpentine)
microsprings. Box microsprings are considered with larger spring constant k and more symmetric
structure keeping balance than zig-zag microspring. Density of spring number, N, is defined as the
numbers of turns within a constant total spring length to investigate performance of box microspring.
With applying the same force, the relation between spring constants and microspring sizes are
discussed. Under different size parameters of box microsprings: B, W, T, and L, the spring constants
decrease like exponential decay and approach a limit value as density of spring number increasing.
The results show density of spring number has significant effect on spring constant. Rate of change on
spring constant, Kt, is defined as the ratio of spring constant between N=1 and N=10. It means
normalization of spring constant that increase density of spring number from minimum to maximum.
The results show Kt decreases when B and W increase and increase as T and L increasing. Therefore,
the spring constant is coupled affected by different size parameters due to different tendency as results
shown. Such that the results can apply in microspring design by adjusting these size parameters to
obtain the spring constant.
Abstract: A computation sample of nanocrystallion metal with a crack is proposed in this work. The
structural evolution scheme is employed to model the mass flow, the grain boundary cavitation, and
the crack growth of the specimen under remote loading. The scheme leads to a system of ordinary
differential equations that can be solved by Euler integration. The simulation validates the proposal
that the ductile versus brittle transition of nano-grained metals is dictated by the competition of creep
deformation promoted by grain-boundary kinetics, and the decohesion of grain boundaries.
Abstract: Anodic alumina has exhibits a homogeneous morphology of parallel pores that can be
easily controlled between 10 and 400 nm. AAO(Anodic Aluminum Oxide) structure is the
transversely isotropic material due to the parallel pores. In this study, mechanical properties of the
AAO structures are measured using the nano-indentation method. Nano-indentation technique is one
of the most effective methods to measure mechanical properties of nano-structures. Investigation of
mechanical properties, such as the indentation modulus and hardness of the AAO structure with
varying nano-pore sizes, was performed using the nano-indentation method. The results showed that
the indentation modulus and hardness decreases monotically as the pore size increases.