Fig. 1: Synthesis of the hierarchical highly ordered nanobowl SnO2@ZnO NWs in situ on MEMS.

a The synthetic protocol for the hierarchical highly ordered nanobowl SnO2@ZnO NWs in situ on MEMS, combining a modified facile hard template method, an ALD process and a hydrothermal method; b the optical microscopy image of the MEMS heating appliance with gas sensing materials; c an enlarged image of heating electrodes and interdigital sensing electrodes