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The hybrid technique of aerosol jet printing and ultraviolet (UV) laser direct writing was developed for 2D patterning of thin film UV curable polydimethylsiloxane (PDMS). A dual atomizer module in an aerosol jet printing system generated aerosol jet streams from material components of the UV curable PDMS individually and enables the mixing in a controlled ratio. Precise control of the aerosol jet printing achieved the layer thickness of UV curable PDMS as thin as 1.6 μm. This aerosol jet printing system is advantageous because of its ability to print uniform thin-film coatings of UV curable PDMS on planar surfaces as well as free-form surfaces without the use of solvents. In addition, the hybrid 2D patterning using the combination of UV laser direct writing and aerosol jet printing achieved selective photo-initiated polymerization of the UV curable PDMS layer with an X-Y resolution of 17.5 μm.

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Conventional stereolithography uses a bath based system, in which a constant layer thickness is applied to realize 3D printing. This approach limits the fabrication of parts consisting of one material only. To overcome this issue, the authors developed a new approach for additive manufacturing using UV curing polymers. In a two step layer-by-layer process, first a liquid monomer film is applied using an Aerosol Jet. Two droplet generators allow the deposition of pure materials as well as various compositions of both materials. In this way, a discrete transition from one pure material to another one from one layer to another is possible. The Aerosol Jet is also able to atomize materials with viscosities greater than 1000 mPa s, allowing a wider range of materials compared to conventional stereolithography. After coating, a laser initiates the one photon polymerization reaction completing one cycle of the layer-by-layer fabrication. In this study, the penetration depth of the raw materials is investigated. In addition, the feasibility of hybrid stereolithography is shown in terms of solid freeform fabrication as well as the multimaterial approach in building direction.

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