A single-axis low-cost accelerometer fabricated using printed-circuit-board techniques

This letter presents a new single-axis low-cost printed-circuit-board (PCB)-based accelerometer. Motivated by the need to develop low-cost human-sensing accelerometer, a capacitive PCB-based microelectromechanical- system (MEMS) accelerometer is developed, and the experimental results of the prototype have demonstrated that the objective is feasible. The PCB-based MEMS accelerometer is fabricated with a metal film adhered to a PCB, which forms the two electrodes of the sensing capacitor of the accelerometer. This signal is compared with the output signal of a commercially available accelerometer, ADXL330, by Analog Devices. The prototypes are designed to have a dynamic range of ±5 g and a bandwidth from 0 to 20 Hz, which covers the range of accelerations for human limbs. The result shows that the new low-cost accelerometer can fulfill the requirement of human motion sensing. © 2009 IEEE.published_or_final_versio

Ambulatory intraocular pressure fluctuation recording with a novel wireless smart silicone contact lens sensor

The Conference program's website is located at http://apacrs2014.org/free_papers.htmlSession - FP1: General: no. FP1-03INTRODUCTION: Monitoring of treatment response in the management of glaucomatous optic neuropathy relies on single intraocular pressure (IOP) measurements during regular clinic hours at regular intervals. However IOP is a dynamic parameter with circadian rhythms as well as posture and exercise related fluctuations. The introduction of continuous 24 hour IOP monitoring technology has created a paradigm shift in glaucoma management. Our wireless smart contact lens sensor was previously validated in-vivo and ex-vivo in animal models. Here we describe the performance of the sensor in ...postprin

Phase transformation of thin wires in tension

A phase transformation constitutive relation including the effect of strain gradient is introduced to examine the extension of a thin wire. The resulting equilibrium equation in terms of strain is a nonlinear (even for small strain deformation) third order differential equation while that of the conventional elasticity theory is only first order and linear for small strain. Additional boundary conditions over those of the conventional theory are needed to make the solution unique and can be derived from a variational functional. The solutions show necking, bulging and periodic striation. We have established the closed form solution for phase transformation with trilinear stress-strain relation and examined the phase transformation behavior in details

In vivo measurement of regional corneal tangent modulus

2017-2018 > Academic research: refereed > Publication in refereed journal201802 bcrcVersion of RecordPublishe

Chemical kinetic model of interfacial degradation of adhesive joints

Mechanical properties of adhesive joints is degraded in the presence of water. The progressive decrease in strength has been attributed to propagation of interfacial crack. Water diffusion and stress distribution within joint as a function of time is modeled using finite element in this study. The stress history at the interface displayed spatially invariant characteristics similar to that of interfacial water concentration history as a function of diffusion. The water-stress history along the interface can be modeled as a function dependent principal on water concentration and is independent of position. On this basis, a chemical kinetic model is proposed to explain the joint strength degradation data reported in literature

Measurement of water evaporation rate from epoxy

Epoxy based materials are used as encapsulant to enhance the reliability of electronic packages. Epoxy is hygroscopic in nature and absorbs water when exposed to humidity. During solder reflow, the absorbed moisture in the package can generate steam pressure at interfacial defect void and drive interfacial delamination leading to popcorn failure of the package. Due to the lack of data, the steam pressure in the defect void has been assumed as a single valued parameter, normally some fraction of the steam saturation pressure at a convenient temperature in popcorning models. A new experimental and analytical methodology to determine the engineering rate of water evaporation from polymer is described in this paper. The evaporation rate from water saturated epoxy is measured by using thermogravitic analysis (TGA). The experimental results indicate that the conventional estimate of water evaporation was found to overestimate the measured rate by nearly two orders of magnitude. To prevent steam driven delamination and popcorning in electronic packaging, the actual evaporation rate should be used in process design as well as material selection of polymer materials

Puncture Depth and the Mechanical Stability of Microneedles

Microneedles penetrating less than 1mm beneath the skin can deliver the drugs directly without piercing blood vessels or damaging nerves. The mechanical stability and the puncture behaviour were investigated experimentally by inserting steel needles into silicone rubber and pig skin. Puncture tests revealed that the length of needle buried in the flesh is less than 50% of the nominal insertion depth when the insertion depth is less 1mm. The mechanical stability of the buried needle-flesh assembly, characterized by the force needed to retract the needle, decreased with buried depth and needle diameter. Analysis of the load data suggested that a 100-micron diameter microneedle buried 100 microns deep in pig skin would have a retraction force of 0.1mN, which is only 1% of the retraction force of a conventional needle inserted 5mm into the skin. This suggests that the usage of microneedles in arrays is necessary to increase stability and to enable stable drug delivery.link_to_subscribed_fulltex

Investigations in size dependent torsions and fractures

Size effects of fine structures due to stain gradients were exhibited experimentally and theoretically in elastic bending of micrometer and nanometer size beams. The Saint-Venant torsion theory of cylinders are extended to explore the relationship between strain gradients and size dependent phenomena. The prediction of the extended torsion theory is in good agreement with experimental data. Furthermore, a higher order J-integral criterion for fracture, which accounts for strain gradients, and its application are reported

A new PCB-based low-cost accelerometer for human motion sensing

IEEE International Conference on Automation and LogisticsThis article presents a new low-cost PCB-based accelerometer. A metal film is adhered to PCB board, which forms the two electrodes of the sensing capacitor of the accelerometer. The sensor signal is proportional to the change of capacitance, and it is obtained by a read-out circuit. This signal is compared with the output signal of a commercially available accelerometer, ADXL330, by Analog Devices. The result shows that the new low-cost accelerometer can fulfill the requirement of human motion sensing. © 2008 IEEE.link_to_subscribed_fulltex

Association between long-term orthokeratology responses and corneal biomechanics

202001 bcmaVersion of RecordPublishe