Sensor Devices Which Benignly Return to the Environment

Every year millions of pounds of expendable sensors are deployed in the oceans of the world. After they finish reporting their measurements they are left to either sink to the bottom or float on the surface until they wash up on some unknown shore. In either case, they are generally built from materials designed to operate reliably in the ocean environment, and as a consequence, persist in the environment unchanged for centuries. 'Ibis does not have to be the case. Many, if not most, of the materials in many commonly used sensor systems, such as sonobouys and expendable bathythermographs, can potentially be replaced with materials that will degrade over a much shorter time span, returning the bulk of the device to the environment in a beneficial, or at least benign, way. This degradation can take several routes. Polymeric components, or components that can be replaced with polymeric components, can be made from materials which are consumed as food by single celled organisms and become part of the food chain. Metallic components can be made from metals, such as magnesium, which are already present at relatively large concentrations in seawater. Through the inclusion of the proper accelerators they can be programmed to rapidly corrode and dissolve, returning to the natural environment they were originally obtained from. It is proposed that these methods, and others, be studied to find ways to produce sensors that can harmlessly disappear into the sea.