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Lab-on-Skin: A Review of Flexible and Stretchable Electronics for Wearable Health Monitoring

Skin is the largest organ of the human body, and it offers a diagnostic interface rich with vital biological signals from the inner organs, blood vessels, muscles, and dermis/epidermis. Soft, flexible, and stretchable electronic devices provide a novel platform to interface with soft tissues for robotic feedback and control, regenerative medicine, and continuous health monitoring.

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SES 2017 Symposium on "Energy Materials"

Dear Colleagues,

We invite you to submit an abstract to "Symposium VI-B: Energy Materials" at the 54rd Annual Technical Meeting of the Society of Engineering Science: SES2017.  More information on the symposium can be found at this link or at the bottom of this message.

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SES 2017 Symposium on "Energy Materials"

Dear Colleagues,

We invite you to submit an abstract to "Symposium VI-B: Energy Materials" at the 54rd Annual Technical Meeting of the Society of Engineering Science: SES2017.  More information on the symposium can be found at this link or at the bottom of this message.

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Measurements of stress and fracture in germanium electrodes of lithium-ion batteries during electrochemical lithiation and delithiation

We measure stresses that develop in sputter-deposited amorphous Ge thin films during electrochemical lithiation and delithiation. Amorphous LixGe electrodes are found to flow plastically at stresses that are significantly smaller than those of their amorphous LixSi counterparts. The stress measurements allow for quantification of the elastic modulus of amorphous LixGe as a function of lithium concentration, indicating a much-reduced stiffness compared to pure Ge.

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Variation of Stress with Charging Rate due to Strain-Rate Sensitivity of Silicon Electrodes of Lithium Ion Batteries

Silicon is a promising anode material for lithium-ion batteries due to its enormous theoretical energy density. Fracture during electrochemical cycling has limited the practical viability of silicon electrodes, but recent studies indicate that fracture can be prevented by taking advantage of lithiation-induced plasticity. In this paper, we provide experimental insight into the nature of plasticity in amorphous LixSi thin films. To do so, we vary the rate of lithiation of amorphous silicon thin films and simultaneously measure stresses.

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Rupture of a highly stretchable acrylic dielectric elastomer (VHB)

Dielectric elastomer transducers are often subject to large tensile stretches and are susceptible to rupture. Here we carry out an experimental study of the rupture behavior of membranes of an acrylic dielectric elastomer (VHB 4905). Pure-shear test specimens are used to measure force-displacement curves, using samples with and without pre-cracks. We find that introducing a pre-crack into a membrane drastically reduces the stretch at rupture. Furthermore, we measure the stretch at rupture and fracture energy using samples of different heights at various stretch-rates. The stretch at rupture is found to decrease with sample height, and the fracture energy is found to increase with stretch-rate.
This paper has appeared in the Journal of Applied Physics and can be downloaded from:

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Rowland Junior Fellows Program Applications

The following message is from Dr. Frans Spaepen at Harvard University:

Dear colleague,

  I am writing to draw your attention to our annual solicitation for
applications to Rowland Junior Fellows Program, which may be of interest to
your graduate students and postdoctoral fellows.

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Fracture Toughness Anisotropy in Silicon Carbide

Here is a paper that I wrote my freshman year of college.  It discusses some observations about fracture toughness in a form of silicon carbide that had potential use in nuclear fission and fusion reactors.  It was published in the Department of Energy's Journal of Undergraduate Research.

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Matt Pharr's First Post

My name is Matt Pharr, and I am a first year graduate student at Harvard in the School of Engineering and Applied Sciences.  I am working with Dr. Zhigang Suo's research group http://www.seas.harvard.edu/suo/ .  My concentration is in solid mechanics, so ES 240 is obviously fundamentally important to my future research.  One of my main goals in this class is to build a solid foundation in solid mechanics.  More specifically, I want to be able to better analyze problems and understand equations in terms of their physical meaning.

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