In this paper, we address the challenge of achieving high throughput with limited number of channels in a wireless sensor network (WSN). The use of multiple channels helps overcome, on one hand, interference generated from inner network activity, and on the other hand, interference caused by neighboring systems operating in the same frequency band. We propose a multi-channel MAC protocol with multi-interface nodes for WSNs. In our proposition, we enhance the channel allocation method of HMC-MAC in order to take into account a multi-interface sink and network segmentation into two groups of nodes. We evaluate our protocol using NS2 simulator with different number of available channels in order to emulate a limited number of interference-free channels. Results show that our MAC protocol improves the overall network performance compared to other protocols with limited number of channels and high data rate traffic.