ORIGINAL ARTICLE Hybrid additive manufacturing (3D printing) and characterization of functionally gradient materials via in situ laser curing Santosh Kumar Parupelli 1,2 & Salil Desai 1,2 Received: 6 March 2020 /Accepted: 5 August 2020 # Springer-Verlag London Ltd., part of Springer Nature 2020 Abstract This paper presents a hybrid additive manufacturing (3D Printing) process for fabricating functionally gradient materials. A multi-axis robot was integrated with microextrusion, picojet, and fiber laser systems to deposit conductive traces of different materials. Laser and furnace curing mechanisms were investigated to evaluate their effect on grain morphology and electrical resistivity of the traces. An increase in the number of laser passes resulted in microstructure evolution from a powder-like to densely packed structure for different materials (Ag, Ni, and C). The laser curing mechanism offered lower resistivity and rapid curing times (< 1 min) compared with furnace curing (> 2 h). Optimal sintering parameters were obtained for 4-pass laser at 18 W with comparable resistivity with bulk materials. Localized infiltration (doping) of nanoparticle silver within the micro-extruded carbon trace demonstrated a significant enhancement in electrical properties (two orders of magnitude reduction in resistivity). The energy dispersive x-ray spectroscopy (EDS) mapping of the infiltrated traces displayed uniform dispersion of nano- particulate silver within the carbon matrix. Multilayer-multi-material (MLMM) traces deposited displayed distinctive morphol- ogy of each constituent material based on in situ laser curing. Scanning electron microscopy revealed distinctive microstructure and graded elemental composition of different layers (FGM) based on targeted laser sintering of individual materials. The versatile hybrid AM platform provides a basis to fabricate functionally gradient materials (FGMs) for electronic components with several applications. Keywords 3D printing . Hybrid additive manufacturing . In situ laser curing: infiltration, Multilayer deposition . Conductivetraces 1 Introduction Electronic components with multifunctional features have promising applications in a wide range of fields [1]. Hybrid electronic 3D structures with embedded functionality can be fabricated with additive manufacturing (AM) by utilizing a combination of several functional materials. 3D printing techniques such as direct-ink writing, inkjet printing, dip-pen nanolithography, laser-induced forward transfer, and electro hydrodynamics printing show good potential in printing qual- ity and speed [1–11]. These direct-write techniques are alter- natives to traditional manufacturing process such as photoli- thography, printed circuit board, and tape casting for fabricat- ing micro scale electronic components. Palmer et al. (2005) were one of the first to explore AM for 3D electronic circuitry [12]. Bidoki et al. (2007) have demonstrated the use of an ink- jet printing technique for depositing metallic conductive pat- terns for creating wiring boards, electrodes, and antennas [13]. Han et al. (2017) have illustrated electro hydrodynamic (EHD) technology potential capability for printing fine metal- lic structures and fabricating electronic components such as self-healing device touch sensors and stretchable devices [14]. Jeong et al. (2011) have demonstrated how stable aqueous based Cu nanoparticle ink can be utilized for printing pre- defined highly conductive features on a plastic substrate [15]. Boley et al.’s (2014) work illustrates the capability of the direct-write method for fabricating an elastomer- Santosh Kumar Parupelli and Salil Desai contributed equally to this work. * Salil Desai sdesai@ncat.edu Santosh Kumar Parupelli sparupel@aggies.ncat.edu 1 Department of Industrial & Systems Engineering, North Carolina A&T State University, 1601 E. Market Street, Greensboro, NC 27401, USA 2 Center of Excellence in Product Design and Advanced Manufacturing, North Carolina A&T State University, 1601 E. Market Street, Greensboro, NC 27401, USA https://doi.org/10.1007/s00170-020-05884-9 / Published online: 13 August 2020 The International Journal of Advanced Manufacturing Technology (2020) 110:543–556