We report on position and density control of nitrogen-vacancy (NV) centres created in type Ib diamond using localised exposure from a helium ion microscope and subsequent annealing. Spatial control to <380 nm has been achieved. We show that the fluorescence lifetime of the created centres decreases with increasing ion dose. Furthermore, we show that for doses >1 Â 10 17 ion/cm 2 , significant damage of the diamond lattice occurs resulting in fluorescence quenching and amorphization. This places an upper limit on the density of NV centres that can be created using this method. V

Mobile sensor networks are often composed of agents with weak processing capabilities and some means of mobility. However, recent developments in embedded systems have enabled more powerful and portable processing units capable of analyzing complex data streams in real time. Systems with such capabilities are able to perform tasks such as 3D visual localization and tracking of targets. They are also well-suited for environmental monitoring using a combination of cameras, microphones, and sensors for temperature, air-quality, and pressure. Still there are few compact platforms that combine state of the art hardware with accessible software, an open source design, and an affordable price. In this paper, we present an indepth comparison of several mobile distributed sensor network platforms, and we introduce the WolfBot platform which offers a balance between capabilities, accessibility, cost and an opendesign. Experiments analyzing its computer-vision capabilities, power consumption, and system integration are provided.Index Terms-Distributed sensing platform, Swarm robotics, Open design platform.

We report on position and density control of nitrogen-vacancy (NV) centres created in type Ib diamond using localised exposure from a helium ion microscope and subsequent annealing. Spatial control to <380 nm has been achieved. We show that the fluorescence lifetime of the created centres decreases with increasing ion dose. Furthermore, we show that for doses >1 Â 10 17 ion/cm 2 , significant damage of the diamond lattice occurs resulting in fluorescence quenching and amorphization. This places an upper limit on the density of NV centres that can be created using this method. V

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