Aerosol Jet 3D Printing
Aerosol Jetting is a process developed by Sandia National Laboratory and commercialized by Optomec for printing microscale patterns on 2D flat/curved surfaces or 3D objects/substrates. The original AJ printing process is two-dimensional, however, during my PhD training I developed a slicer to take a 3D lattice geometry and generate tool path for the Aerosol Jet printer to create 3D complex structure. This micro 3D printing technique can be used for fabrication of Micro-Electrode Arrays, Micro lattice batteries, and MEMS microdevices.
3D Printed Micro-Electrod Arrays (Neural Probes)
A picture of the most dense 3D printed Micro Electrode Array (2019).
This 10 by 10 array of vertical electrodes is made of silver and can be used for research and scientific purposes in acute implantations for electrophysiological signal acquisition from a neurologically active tissue such as a rodent cortex tissue. The substrate is a hard dense alumina ​plate, and can be inverted on a soft pcb sheet such as Polyamide for ease of installation and flexibility. Pitch length between two adjacent electrodes is 250um (1600 electrodes pr cm^2) and approximate height of each shank is 750um. This array is printed on top of a four-layer micro electrical routing. The routing layers are made of silver and coated with a layer of dielectric (Polyamide).
A similar electrode array 4 by 4 printed on a flexible substrate with direct routing to the back end connector. The microprobe is measuring the impedance of single electrodes and some are as low as 100kOhm.
3D Printing offers flexibility in pattering and shaping the height profile of micro electrode arrays. The ceramic nozzle and the metallic shutter shown in this picture, generate micro droplets of highly dense silver nano dispersion.
The 3D printing process starts by atomizing the nanoparticle dispersion of the target material, generating an aerosol of microdroplets carrying the nanoparticles. The aerosol is being directed to the pneumatic focusing mechanism that collimates the aerosol to a fine stream of dense material. Later a shutter breaks this flow of the dense material to micro droplets. By stacking these microdroplets, a single shank of electrode can be printed and later sintered to gain strength and reach final conductivity.
