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Data collection architectures for static sensor networks typically adopt a multipoint-to-point routing model in which data from individual sensors is routed to strategically placed static sink units. In spite of its operational simplicity, this model suffers from uneven energy burden in the network due to the high routing energy expenditure around the static sink units. This can lead to limited network life caused by sink disconnections due to the early energy exhaustion of those energy-strained nodes near the data sinks. Introducing sink mobility to combat this lifetime issue has recently generated a lot of interest among the sensor network research community. The key idea is to avoid routing hotspots using policybased sink mobility for improving network life. This article first explores and categorizes the general problem of sink mobility in the context of trade-offs between data delivery delay and network lifetime. Then it reviews a number of existing solutions in the literature and their applicability to various application scenarios. Finally, the article introduces and studies a novel mobility control solution in which the network nodes cooperatively determine the sink trajectory, and navigate the mobile sinks for delay and energy optimized data collection.