Processing of Janus micropillars based on femtosecond laser and vacuum evaporation

As a new bottom-up processing method, femtosecond laser two-photon polymerization (TPP) technology, has the advantages of simple working environment, high resolution and flexibility, which is widely used in the fields of micro-optical devices, micro-mechanical devices and micro-fluid devices. Structures with different chemical or physical properties on either side are called Janus structures. In particular, when there is difference in expansion coefficient between the two sides of the Janus structure in different external environments, the structure as a whole will show shape changes controlled by the external environment, so processing Janus structure is an important way to achieve structural deformation. The key to prepare the Janus structure is the uniformity of the diprosopic structure itself. At first, we fabricate ordinary micropillars by focusing controllable femtosecond laser into photoresist (SZ2080). Then the vacuum evaporation technology is used to transform the ordinary micropillars into Janus micropillars by steaming metal on one side of the micropillars. These Janus micropillars will have a directional bending towards the side of coating metal. This phenomenon is analyzed theoretically and simulated numerically by COMSOL, which is verified by experiments. Since the thermal expansion coefficients of different materials on both sides of the micropillar are different, these Janus micropillars have the ability to change their shapes with the change of temperature, which have potential applications in temperature drive and temperature sensing.