Yufridin Wahab

Foot Plantar Pressure Measurement System: A Review

Foot plantar pressure is the pressure field that acts between the foot and the support surface during everyday locomotor activities. Information derived from such pressure measures is important in gait and posture research for diagnosing lower limb problems, footwear design, sport biomechanics, injury prevention and other applications. This paper reviews foot plantar sensors characteristics as reported in the literature in addition to foot plantar pressure measurement systems applied to a variety of research problems. Strengths and limitations of current systems are discussed and a wireless foot plantar pressure system is proposed suitable for measuring high pressure distributions under the foot with high accuracy and reliability. The novel system is based on highly linear pressure sensors with no hysteresis.

Gait analysis measurement for sport application based on ultrasonic system

Gait analysis is a very important procedure in assessing and improving many quality of life indicators. In sports, gait analysis can be used to improve athletes performance and injury prevention. This paper presents the development of ultrasonic system in wearable instrumented shoes for gait analysis measurement in sport application. This paper begins with introduce to the requirement in the related literature. The explanation on the system configuration follows next that describes sensor properties and time of flight concept. Next, is a section that explains the experimental setup using the proposed instrumentation which is then followed by the result section. Finally, the planned future works shares in this paper.

Design of MEMS biomedical pressure sensor for gait analysis

Measurement of the foot and shoe interface pressure underpins a number of important applications. Abnormal pressure may indicate instability in gait, risks of diabetic ulceration and many other biomedical and sports applications. As the current foot pressure sensors in the market exhibit many limitations, a new sensor design based on the more promising MEMS technology was therefore explored. As such, this paper reports the analysis and optimization of a MEMS pressure sensor for foot pressure measurement. The pressure sensor had a high linearity output with pressure span of more than 2-MPa. This characteristic indicates excellent potential for a wide spectrum of biomechanical activities.

Microsystem based portable shoe integrated instrumentation using ultrasonic for gait analysis measurement

Mobility stage, hidden chronic disease and aging effect can be detected by use of gait pattern. The gait pattern is normally directly related to the foot and leg health, in addition to other significant factors. Therefore the foot is the most important part of gait system and thus directly affects the gait pattern. This paper reports the development of microsystem based portable shoe integrated gait analysis instrumentation. This paper begins with the related literature where the requirement is introduced. The explanation on the system architecture follows next that describes sensor properties and proposed sensor placement. Next, is a section that explains the experimental setup using the proposed instrumentation which is then followed by the results section. Finally, this paper shares the planned future works.

From ambient vibrations to green energy source: MEMS piezoelectric energy harvester for low frequency application

Using piezoelectric materials to harvest the ambient vibrations that surround a system is one method that has seen a dramatic rise in the power-harvesting applications. The simplicity associated with piezoelectric micro-generators makes them very attractive for MEMS applications in which ambient vibrations are harvested and converted into electric energy. These micro generators can become an alternative to the battery-based solutions in the future, especially for remote systems. In this paper, we proposed a model and presented the simulation of a MEMS-based arrayed energy harvester under ambient vibration excitation using the Coventorware approach. This arrayed cantilever-based MEMS energy harvester that operates under ambient excitation of frequency band of 67 to 70 Hz, within a base acceleration of 0.2 to 1.3 g produces an output power of 6.8 μw and 0.4 volts at 20.1 k-ohms load.

The effect of softbaking temperature on SU-8 photoresist performance

One of the steps required during the fabrication of SU-8 mold for soft lithography is softbaking, which is conducted after the deposition of the photoresist. The purpose of softbaking is to stabilize the resist film and eliminate any remaining solvent through evaporation. This ensures that the resist surface is non-sticking, hence avoiding debris when transferring the patterns later. In this paper, we investigate the effects of softbaking temperature on the polymerization of SU-8 photoresist. The significance of this work is to optimize the fabrication process involved in producing SU-8 mold structures with thickness of 30 μm. This project involves a series of experiments covering softbaking temperatures ranging from 45° to 115° C. Experiments results show that softbaking temperature of 85°C results in completely stick and crack free structures. By this, a huge improvement obtained if compared to the result of processing at the standard soft bake temperature of 95°C. The soft bake temperature should not be taken lightly while optimizing SU-8 processing because it has a big influence on the material properties and the lithographic performance of the resist.

MEMS Biomedical Sensor for Gait Analysis

Gait analysis is the study of lower limb movement patterns and involves the identification of gait events and the measurements of kinetics and kinematics parameters. These include for example, toe-off, landing, stance, swing, displacement, speed, acceleration, force, pressure and the pressure-time-integral. Gait analysis is a very important procedure in assessing and improving many quality of life indicators. In sports, gait analysis can be used to improve athlete’s performance and injury prevention. For patients, such as those suffering from diabetes, gait analysis can be used to screen for development of foot ulceration thus preventing them. In term of gait stability, gait analysis is proven to be very helpful in assessing and improving balance among the elderly, patients with diabetes or peripheral neuropathy and many other sicknesses. Gait analysis is also widely used in rehabilitation. The occurrence of fall is becoming more of a significant health threat recently. This is due to the fact that the worldwide phenomenon of growing population of the elderly is continuously observed in many developed and developing countries. It is estimated that the world’s elderly citizen will reach 2 billion in 2050 from current figure of 670 million. To make matters worse, the total number of the world’s diabetic sufferers is increasing from 171 million in 2000 to 366 million in 2030, with an obvious trend of surging proportion for the above 65 years group. In order to further understand the situation that leads to the health hazard, many research groups around the world are seriously looking into the matter. Recently, it is reported that foot plantar pressure can be used to asses gait stability and risk of fall. In addition, foot clearance above ground/floor during gait is also reported to be related to the occurrence of fall among the elderly. This is especially true when the foot is swaying on the air, or also called swing phase. Notably, pressure is measured when the foot is already touching the ground, which is known as stance phase, while clearance is measured during mid-swing to heel strike. If both pressure and clearance parameters of gait analysis are used together in an integrated manner, a better way of fall prediction and prevention can be produced. In addition to assessing balance, the measurement of foot plantar pressure and foot clearance are also useful in many other gait assessments. This foot pressure measurement has wide applications, for example in screening for high risk diabetic foot ulceration, design of orthotics for diabetes mellitus and peripheral neuropathy, footwear design, sports injury prevention in athletes, study of the development of gait among the children plus many more. It also can be used to identify gait events such as heel strike, toe off, the timing of swing, stance, stride, the double support phase and also cadence. If stride length is known,

Etch Performance of KRF Excimer Laser Micromachining Characterization on Silicon Material

Excimer laser micromachining enables us to overcome the conventional lithography-based microfabrication limitations and simplify the process of creating three dimensional (3D) microstructures.The objective of this study is to investigate the relation between the number of laser pulses, number of laser passes through the channel of ablation site and their etch performance. Parameters such as frequency, fluence and velocity were retained as constants. In this paper, we present a parametric characterization study on silicon using KrF excimer laser micromachining. From the result, the etch rate change were recorded as the two major laser parameters (Number of laser pulses and number of laser passes) were varied. Both parameters were showing declination profile however from comparing both graphs, it showed that etch rate dropped more steeply when varied number of laser passes rather than number of pulses.

Characterization of MEMS structure on silicon wafer using KrF excimer laser micromachining

This paper presents preliminary parametric studies of KrF laser micromachining ablation effects on Silicon. Four parameters are studied, namely laser energy, pulse rate, number of laser pulses, and Rectangular Variable Aperture (RVA) in X and Y direction. At present, the study is focused on the production of microchannels using laser micromachine, in which its dimension is examined and measured. We found that the number of laser pulse is non-linearly proportional with the ablated channel width, with the etching rate of approximately 1 to 5 um for 50 laser pulses. This is similar with the measured depth of the microchannel. The changes in the measured channel width are most significant when the laser energy is increased. Some debris and recast can also be observed around the edge of the microchannel particularly during the variation of the laser pulse frequency. When varying the RVA, it is observed that the surfaces of the ablated microchannels are not smooth with a lot of debris accumulated at the channel edge and a few discolorations. Finally, a microcantilever structure is fabricated with the aim of demonstrating the capability of the laser micromachine.

Modelling of Critical Slopes of Gait Patterns for the Realization of a Wireless Foot Clearance Measurement

Gait analysis measurement is a method to access and identify gait events and the measurements of dynamic and motion parameters involving the lower part of body. This significant method is widely used in sports, rehabilitation as well as the health diagnostic towards improving the quality of life. Many researchers has proposed various ways to access gait features that require specially set-up motion laboratories, highend video based-motion imaging systems, and professionals to visually observe the gait, this makes current way of accessing gait to be very costly and limited in many ways.Therefore, this research focuses on design and development of a portable shoe integrated wireless MEMS-based and recent microelectronic based foot clearance measurement system that is cheap, portable, real life and can be used by more people. The foot clearance measurement is representing the measurement of the distance between foot and ground. The clearance measured by an ultrasonic sensor. The system was tested and proven to satisfy the gait analysis requirement.