A new research paper from Exaddon and EMPA details how highly conductive gold micro structures can be 3D printed directly on pre-patterned microchips via localized electrodeposition. 

Tests revealed that Exaddon’s 3D printing method can achieve conductivity values for gold and copper which are comparable to those found in structures fabricated by established 2D deposition methods, thus delivering both excellent design freedom and excellent material properties.

These results point toward superior functionality and device performance through use of locally electrodeposited gold; a very promising development for applications such as microelectronics, biomedical engineering, high frequency communications, and photonics. 

A test device was created by 3D printing gold microwires orthogonally across pre-patterned gold electrodes, produced by conventional photolithography on a silicon chip. This enabled the electrical characterization of printed material in a scenario which replicates intended real-world applications, such as microneedles for use as neural implants in brain-machine interfaces (BCIs). 

Four-point probe measurement of the gold microwires showed a resistivity of 65 ± 6 nΩm; an excellent value compared to gold conventionally electrodeposited out of thiosulfate-based solutions without post-processing. Microstructural analysis (FIB, EDX) of the gold wires revealed a dense metal deposit free of voids. 

Full paper:
Schürch P, Osenberg D, Testa P, et al. Direct 3D microprinting of highly conductive gold structures via localized electrodeposition. Materials & Design 2023, 111780. https://doi.org/10.1016/j.matdes.2023.111780.