An important trend in electronics involves the development of materials, mechanical designs and manufacturing strategies that enable the use of unconventional substrates, such as polymer films, metal foils, paper sheets or rubber slabs. The last possibility is particularly challenging because the systems must accommodate not only bending but also stretching. Although several approaches are available for the electronics, a persistent difficulty is in power supplies that have similar mechanical properties, to allow their co-integration with the electronics. Here we introduce a set of materials and design concepts for a rechargeable lithium ion battery technology that exploits thin, low modulus silicone elastomers as substrates, with a segmented design in the active materials, and unusual 'self-similar' interconnect structures between them. The result enables reversible levels of stretchability up to 300%, while maintaining capacity densities of B1.1 mAh cm À 2 . Stretchable wireless power transmission systems provide the means to charge these types of batteries, without direct physical contact.

Laser photocoagulation of the myocardium effectively destroys arrhythmogenic foci. The purpose of this study was 1) to compare the optical properties of canine myocardium before and after photocoagulation, 2) to compare the canine model with clinical cases by measuring the optical properties of human myocardium, and 3) to assess the optical properties of human myocardial scar and epicardial fat tissue. Measured optical properties were the absorption coefficient, mu a; scattering coefficient, mu s; and scattering anisotropy factor, g. Optical measurements were performed at 1064 nm wavelength on thin plane parallel tissue slices using the integrating sphere method with glass hemispheres on either side of the sample. The study showed 1) an increase of the scattering coefficient by 40% and a two- to threefold increase in reduced scattering coefficient as a result of photocoagulation; 2) that the mu a (0.035 +/- 0.024 mm-1) and mu s (17.9 +/- 3.8 mm-1) of human myocardium were not significantly different from mu a (0.043 +/- 0.021 mm-1) and mu s (17.3 +/- 2.2 mm-1) of canine myocardium, whereas the human g (0.964 +/- 0.005) was slightly different from the canine g (0.974 +/- 0.008); and 3) that the mu a (0.021 +/- 0.016 mm-1) of epicardial fat and mu s (13.8 +/- 1.1 mm-1) of myocardial scar were significantly lower than those of normal myocardium. A dynamic model of laser-tissue interaction incorporating these changes and inhomogeneities is necessary to better describe light distribution during laser photocoagulation.

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