Micro-powered wireless sensors present new challenges due to the severe harvesting conditions under which they need to operate and their tiny energy reservoirs. However, existing lowpower network stacks make a slew of design choices that limit the ability to scale down to such environments. We address these issues with QuarkNet, a backscatter-based network stack that is designed to enable continuous communication even if there is only enough harvested energy to transmit a few bits at a time while simultaneously optimizing throughput across a network of micro-powered devices. We design and implement QuarkNet on a software radio based RFID reader and the UMass Moo platform, and show that QuarkNet increases the communication distance by 3.5 over Dewdrop, 9 over Buzz, and is within 96% of the upper bound of achievable range. QuarkNet also improves the communication throughput by 10.5 over EPC Gen 2, 5.8 over Dewdrop, and 3.3 over Flit for tag-to-reader communication and by 1.5 over EPC Gen 2 for reader-to-tag communication.