A structure for use in an energy storage device, the structure comprising a backbone system extending generally perpendicularly from a reference plane, and a population of microstructured anodically active material layers supported by the lateral surfaces of the backbones, each of the microstructured anodically active material layers having a void volume fraction of at least 0. A sample holder for isolating a fraction of interest from a physiological fluid sample includes a flexible compartment and a rigid exoskeleton that supports the flexible compartment. An oxide layer such as a thermal oxide is located on a surface of the semiconductor substrate.