Abstract
A combined approach of laser-induced forward transfer (LIFT) and chemical etching of pure metal films is studied to fabricate complex, free-standing, 3-dimensional gold structures on the few micron scale. A picosecond pulsed laser source with 515 nm central wavelength is used to deposit metal droplets of copper and gold in a sequential fashion. After transfer, chemical etching in ferric chloride completely removes the mechanical Cu support leaving a final free-standing gold structure. Unprecedented feature sizes of smaller than 10 μm are achieved with surface roughness of 0.3 to 0.7 μm. Formation of interfacial mixing volumes between the two metals is not found confirming the viability of the approach.
Highlights
The ability to fabricate metallic microstructures plays an important role for several sectors of technology, such as electronics, photonics, plasmonics, micromechanics and biomedical technology [1,2]
We show laser-induced forward transfer (LIFT)-printing of metallic structures using this sacrificial approach investigating optimized processing parameters, as well as studying the interaction of Cu and Au during LIFT and after etching, crucial to determine the feasibility of this technique for the fabrication of complex 3D structures
The spatial feature sizes for in-plane structures were below 5 μm and below 1 μm for single deposits
Summary
The ability to fabricate metallic microstructures plays an important role for several sectors of technology, such as electronics, photonics, plasmonics, micromechanics and biomedical technology [1,2]. Additive manufacturing technologies, such as laser microcladding, fused deposition modelling and multiphoton polymerization have been intensively developed in recent years [3,4,5,6] Such 3D printing methods do permit the design of novel features not possible with conventional fabrication techniques, and they can potentially save energy and material usage. This technique requires a further wet-chemical process step, it will be shown that the structure or composition of the deposited structure remains unchanged, preserving some of the main advantages of LIFT This combined method has been used previously in LIFT, but was not studied for feature sizes in the few micron range [13,14].
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