Enhanced Liquid Metal Micro Droplet Generation by Pneumatic Actuation Based on the StarJet Method

Abstract

Abstract:We present a novel pneumatic actuation system for generation of liquid metal droplets according to the so-called StarJet method. In contrast to our previous work, the performance of the device has been significantly improved: the maximum droplet generation frequency in continuous mode has been increased to f max = 11 kHz (formerly f max = 4 kHz). In addition, the droplet diameter has been reduced to 60 μm. Therefore, a new fabrication process for the silicon nozzle chips has been developed enabling the production of smaller nozzle chips with higher surface quality. The size of the metal reservoir has been increased to hold up to 22 mL liquid metal and the performance and durability of the actuator has been improved by using stainless steel and a second pneumatic connection to control the sheath flow. Experimental results are presented regarding the characterization of the droplet generation, as well as printed metal structures.

Laser Transfer of Metals and Metal Alloys for Digital Microfabrication of 3D Objects

“…The third category of metal printing, which is the focus of this article, consists of transferring molten metal from the bulk phase. One way of doing this is similar to the previously mentioned dispensing methods, but here the dispenser is made of a thermally resistant material, which must be chosen according to the melting temperature of the metal to be transferred . These methods clearly favor the transfer of metals with low melting temperature such as gallium alloys, solder, and aluminum, and they become more complex for metals with high melting temperature.…”

Direct fabrication of unsupported inclined aluminum pillars based on uniform micro droplets deposition

“…In uniform micro metal droplet deposition technique, the frequency range is usually from zero to several thousand hertz [27]. In the low frequency range, the stable and controllable columnar morphology can be kept in the deposition of inclined pillar [4,5].…”

Beamless Metal Additive Manufacturing

“…Droplets as small as around 60% [27] and 55% [28] of the nozzle diameter could be printed using a new pneumatic DOD and impact-driven ejection, respectively. To improve uniformity and accuracy of metal droplets, a pneumatically actuated inkjet printing system composed of a star-shaped nozzle was proposed for the generation of liquid metal microdroplets in the nano-to picoliter range [29,30]. High resolution pillars and microstructures with wall thickness of 25 µm could be printed using laser-induced forward transfer (LIFT) print heads that use laser beam to melt a thin metal layer for creating femtoliter droplets [31].…”