Ablation medical devices

Medical devices and methods for making and using medical devices are disclosed. An example medical device includes an ablation system. The ablation system may include an elongate shaft having a distal region. A plurality of ablation tines may be disposed at the distal region. Each of the ablation tines may include a tubular member having a flexible circuit disposed therein. The flexible circuit may include a substrate, one or more electrodes coupled to the substrate, and a temperature sensor coupled to the substrate and positioned adjacent to the one or more electrodes. The plurality of ablation tines may include a first ablation tine and a second ablation tine. A pair of bipolar electrodes may defined by a first electrode disposed at the first ablation tine and a second electrode disposed at the second ablation tine.