How To Do SHEATH GAS-ASSISTED ELECTROHYDRODYNAMIC DIRECT WRITING

To further improve the deposition behavior, a core-shell-shaped spinneret has been designed and in this design a sheath gas goes out from the peripheral channel to travel around the jet. The sheath gas provides an additional stretching and focusing force on the ejecting jet, which is beneficial to overcoming interference from the surrounding environment and gaining precise micropatterns. He et al. utilized sheath gas to fabricate micro/nanostructures under a lower applied voltage. With the help of the stretching force stemming from the sheath gas, the initiation voltage and sustaining voltage decrease obviously. Low applied voltage is helpful to restrain the instability of the printing process and promote the integration fabrication of micro/nanodevices. The average diameter of the micro/nanostructure decreases from 21.58 mm to 505.58 nm when the assisted gas pressure increases to 50 kPa. In addition, based on the same setup, Zheng et al. investigated the patterned deposition behavior of a charged jet. With the help of a sheath gas, the surrounding interference can be weakened and the charged jet can be free from the influence of the microstructures. Fig. 9.16 shows that precise complex micropatterns such as parallel lines and grids can be direct written with position precision to less than 5 mm.

How To Fabricate ZnO Gas Sensor Using Near-Field Electrospray

In addition, a thin-film ZnO gas sensor was fabricated by using near-field electrospray, as shown in Fig. 9.8. Comb electrodes with a large contact area were printed to increase the sensitivity of micro/nanosensors. The electrospray micro/nanoparticles were deposited over the electrodes, which would be heated and oxidized to form a ZnO semiconductor at 500℃ afterward. The experimental results showed that the fabricated sensor displays high sensitivity because of the small diameter and high specific surface area of the electrospray particles, indicating a new promising method for the integration fabrication of micro/nanodevices.