Keith Choon Chiang Foo

Keith Choon Chiang Foo
Institute Of High Performance Computing · Engineering Mechanics

PhD. (Mech. Eng.)

About

38
Publications
29,602
Reads
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3,194
Citations
Additional affiliations
December 2012 - present
Institute Of High Performance Computing
Position
  • Scientist and Capability Group Manager (Soft Matter)
Description
  • We develop theoretical models and computational tools to understand the mechanical behavior of soft materials, which are being developed for use in engineering and biomedical applications.
November 2010 - November 2012
Harvard University
Position
  • PostDoc Position
Description
  • My research at Harvard focuses on the mechanics of soft active materials, in particular dielectric elastomers and their applications as actuators and generators.
September 2008 - October 2010
Institute Of High Performance Computing
Position
  • Engineer
Education
July 2004 - July 2008
Nanyang Technological University
Field of study
  • Mechanical Engineering
July 2000 - July 2004
Nanyang Technological University
Field of study
  • Mechanical Engineering

Publications

Publications (38)
Article
Full-text available
Existing stretchable, transparent conductors are mostly electronic conductors. They limit the performance of interconnects, sensors, and actuators as components of stretchable electronics and soft machines. We describe a class of devices enabled by ionic conductors that are highly stretchable, fully transparent to light of all colors, and capable o...
Article
Full-text available
Viscoelasticity is known to adversely affect the performance of a dielectric elastomer actuator and limit its application. In this paper, we present a finite element method for dielectric elastomers based on a nonlinear field theory that couples viscoelasticity and electrostatics. This method is implemented in a commercial finite element software....
Article
This paper reports an untethered soft robot using soft electrostatic actuators. The robot consists of a deformable body driven by dielectric elastomer actuators, and two paper-based feet driven by electroadhesion actuators. The use of light-weight batteries and small-volume amplifiers contributes to the development of this untethered soft robot. In...
Article
Dissipative processes such as viscoelasticity and current leakage are known to affect the electromechanical performance of dielectric elastomers. In this work, we describe a constitutive theory that couples electrostatics, large deformation, viscoelasticity, and current leakage. We also implement this model in a commercial finite element solver ABA...
Article
Full-text available
The dynamic performance of dielectric elastomer transducers and their capability of electromechanical energy conversion are affected by dissipative processes, such as viscoelasticity, dielectric relaxation, and current leakage. This paper describes a method to construct a model of dissipative dielectric elastomers on the basis of nonequilibrium the...
Article
The metamaterial sensor array has the ability to conform to a spherical surface as shown. The slight separation between the array and the sphere implies that the array is not only limited to a spherical surface but can conform to other curved surfaces. A blown‐up view shows capacitive sensor electrodes being embedded within the metamaterial sensor...
Article
Full-text available
Existing stretchable capacitive sensor arrays face challenges in decoupling normal forces and stretch stimuli which restrict its applications into soft robotics. Herein, a metamaterial capacitive sensor array with 6 × 6 sensors is developed for the detection of normal forces on curved deforming surfaces common to both the soft universal jamming gri...
Article
Full-text available
Rapid energy‐efficient movements are one of nature's greatest developments. Mechanisms like snap‐buckling allow plants like the Venus flytrap to close the terminal lobes of their leaves at barely perceptible speed. Here, a soft balloon actuator is presented, which is inspired by such mechanical instabilities and creates safe, giant, and fast deform...
Article
Full-text available
Explosion of ping‐pong balls that is caused by the rapid inflation of an elastomer membrane. The illustrated ultrafast actuation is based on a plant‐inspired mechanical instability that occurs in natural rubber and can be remotely triggered, presented in article number 1903391 by Martin Kaltenbrunner and co‐workers. These new types of high‐speed so...
Article
Full-text available
The buoyancy control mechanism is critical for undersea robots to achieve effective vertical motion. However, current buoyancy control mechanisms are associated with problems such as complex design, bulky structure, noisy operation and slow response. Inspired by the swim bladder of natural fish, we develop an artificial swim bladder, using dual mem...
Article
Full-text available
Transparency is a surprisingly effective method to achieve camouflage and has been widely adapted by natural animals. However, it is challenging to replicate in synthetic systems. Herein, a transparent soft robot is developed, which can achieve effective camouflage. Specifically, this robot is driven by transparent dielectric elastomer actuators (D...
Article
Instabilities in a thin sheet are ubiquitous and can be induced by various stimuli, such as a uniaxial force, a liquid-vapor surface tension, etc. This paper investigates voltage-induced instabilities in a membrane of a dielectric elastomer. Instabilities including buckling, wrinkling, and crumpling are observed in the experiments. The prestretches...
Article
Origami has emerged as a powerful methodology for developing intelligent transformable robots. Although there is considerable progress in origami techniques to enable the design of a broad range of geometries, there is a dearth of effective actuation mechanisms which can eliminate the complex process of assembling external actuators. This paper ill...
Article
We propose a multi-field implicit finite element method for analyzing the electromechanical behavior of dielectric elastomers. This method is based on a four-field variational principle, which includes displacement and electric potential for the electromechanical coupling analysis, and additional independent fields to address the incompressible con...
Article
Full-text available
Giant deformation of the dielectric elastomer (DE) via electromechanical instability (or the “snap-through” phenomenon) is a promising mechanism for large-volume fluid pumping. Snap-through of a DE membrane coupled with compressible air has been previously investigated. However, the physics behind reversible snap-through of a DE diaphragm coupled w...
Article
A dielectric elastomer transducer is a deformable capacitor, and is under development as a sensor, actuator, or generator. Among various geometric configurations, laterally-constrained transducer, also known as pure-shear transducer, is easy to implement and effective to couple mechanical force and electrical voltage. This analytical study reveals...
Article
A membrane of a dielectric elastomer may undergo electromechanical phase transition from the flat to wrinkled state, when the applied voltage reaches a critical value. The wrinkled region is observed to expand at the expense of the flat region during phase transition. In this paper, we report on a dynamic pattern of wrinkles in a circular membrane...
Article
A duct silencer with tunable acoustic characteristics is presented in this paper. Dielectric elastomer, a smart material with lightweight, high elastic energy density and large deformation under high direct current/alternating current voltages, was used to fabricate this duct silencer. The acoustic performances and tunable mechanisms of this duct s...
Article
Full-text available
A dielectric elastomer actuator is one class of soft actuators which can deform in response to voltage. Dielectric elastomer actuators coupled with liquid have recently been developed as soft pumps, soft lenses, Braille displays, etc. In this paper, we conduct experiments to investigate the performance of a dielectric elastomer actuator which is co...
Article
Full-text available
A novel semi-explicit finite element method is proposed to analyze dynamic electrome-chanical coupling behavior of dielectric elastomers. The method consists of an explicit solver to update the velocity field and an implicit solver to update the electric voltage. The electromechanical coupling is realized by including the Maxwell stress in the expl...
Article
Dielectric elastomer actuators coupled with liquid have recently been developed as soft pumps, soft lenses, Braille displays, etc. In this paper, we investigate the performance of a dielectric elastomer actuator, which is coupled with water. The experiments demonstrate that the membrane of a dielectric elastomer can achieve a giant voltage-induced...
Article
Full-text available
Clean, renewable and abundant sources of energy, such as the vast energy of ocean waves, are untapped today, because no technology exists to convert such mechanical motions to electricity economically. Other sources of mechanical energy, such as motions of people and vibrations of buildings and bridges, can potentially power portable electronics an...
Article
Full-text available
In the nascent field of soft machines, soft materials are used to create devices that actuate robots, sense environment, monitor health, and harvest energy. The soft materials undergo large deformation in response to external stimuli, often leading to instability that is usually undesirable but sometimes useful. Here, we study a dielectric elastome...
Data
Full-text available
Hydrogels containing electrolyte can work as ionic conductors to actuate dielectric elastomer (DE) artificial muscles. Based on a popular design of a circular actuator, we study theoretically and experimentally the cyclic performance of acrylic DE actuators with solid hydrogel electrodes. The viscoelasticity of solid electrodes constrains the maxim...
Article
Full-text available
For many applications of dielectric elastomer actuators, it is desirable to replace the carbon-grease electrodes with stretchable, solid-state electrodes. Here, we attach thin layers of a conducting silicone elastomer to prestrained films of an acrylic dielectric elastomer and achieve voltage-actuated areal strains over 70%. The influence of the stif...
Article
Full-text available
Dielectric elastomer generators are high-energy-density electromechanical transducers. Their performance is affected by dissipative losses. This paper presents a theoretical analysis of a dielectric elastomer generator with two dissipative processes: viscoelasticity and current leakage. Conversion cycles are shown to attain steady-state after sever...
Article
Full-text available
Far greater voltage-actuated deformation is achievable for a dielectric elastomer under equal-biaxial dead load than under rigid constraint usually employed. Areal strains of 488% are demonstrated. The dead load suppresses electric breakdown, enabling the elastomer to survive the snap-through electromechanical instability. The breakdown voltage is...
Article
An energy-balance model is often used to analyze impact dynamics for composite structures. However this model tends to overestimate the peak impact load after the onset of damage since it does not account for damage initiation and propagation. In this paper, the energy-balance model is coupled with the law of conservation of momentum to extend its...
Article
Full-text available
In this paper, the failure response of aluminium sandwich panels subjected to low-velocity impact is discussed. A three-dimensional geometrically correct finite element model of the honeycomb sandwich plate and a rigid impactor was developed using the commercial software, ABAQUS. This discrete modelling approach enabled further understanding of the...
Article
Composite sandwich structures are susceptible to low-velocity impact damage, but existing elastic impact models cease to be valid after the onset of damage. In this paper, a modified energy-balance model coupled with the law of conservation of momentum is proposed to extend its validity beyond the elastic regime. Three parameters were first derived...
Article
Full-text available
This paper presents extensive test results of linear elastic mechanical properties of Nomex paper and Nomex honeycomb structures. The fundamental mechanical properties of the Nomex paper are then used in the finite element modeling and analysis of Nomex honeycomb structures. The finite element results are then compared with the experimental results...
Article
Full-text available
This article presents an extensive experimental and numerical investigation of aluminium sandwich plates subjected to quasi-static loading and low-velocity impact. The objective of this research is to understand and, ultimately, predict the initiation and progression of damage in an aluminium sandwich plate subjected to low-velocity impact. The sta...
Article
Full-text available
This dissertation presents experimental, numerical and analytical investigations of sandwich plates subjected to quasi-static loading and low-velocity impact. The objectives of this research are to predict the low-velocity impact response and damage in a sandwich structure, and to characterise the energy absorbed by the structure. Aluminium sandwic...

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Projects

Projects (2)
Project
Unlike traditional machines designed by humans in engineering, machines in nature use soft materials. Examples for the latter include a beating heart or muscles contracting to lift weights. One emerging field in engineering is the use of soft active materials to create soft machines. In this project, we are interested in the fundamental mechanics and physics of materials and phenomena emerging in this new class of devices. We also draw inspirations from nature to design new materials and structures with remarkable functions for novel engineering applications.