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The hybridization of direct write (DW) and additive manufacturing (AM) technologies to create additively manufactured electronics (AME) has enabled the integration of electrical functionality to form multifunctional AM components. Current work in AME has demonstrated the integration of conductive traces into and onto geometries and form factors that are not possible through traditional electronics packaging processes. This has largely been accomplished by using AM and DW technology to deposit conductive inks to form interconnects on the surface of AM substrates or within multimaterial AM geometries. However, the requisite thermal post-processing and high resistivity of the conductive inks and the limitations in thermal and dielectric performance of printable substrates commonly used in AME restrict the capabilities of these parts. This thesis proposes an alternative process for the conformal deposition of low resistivity traces on additively manufactured all-aromatic polyimides (AM-PI) without the use of conductive inks. This is accomplished through the selective patterning of laser induced graphene (LIG), a porous 3D graphene fabricated via laser irradiation, onto the AM-PI. While the resultant LIG is conductive, its resistivity is further reduced by the electrodeposition of copper (Cu-LIG). In this thesis, the synthesis of LIG on AM-PI, thermally post processed to 240℃, 300℃, and 450℃, is demonstrated and characterized through sheet resistance measurements and Raman spectroscopy. AM-PI post-processed to 300℃ demonstrated the lowest resistivity LIG formation (13.8 Ω/square). The resistivity of Cu-LIG is compared to an industry standard silver ink (Micromax CB028) used in direct write hybrid manufacturing applications. Cu-LIG was found to have a measured resistivity (1.39e-7 Ω·m), two orders of magnitude lower than the measured resistivity of the CB028 silver ink (1.62e-5 Ω·m). Additionally, the current capacity of the Cu-LIG was demonstrated and Joule heating of the material was observed via IR thermography. Cu-LIG demonstrated no failure of conductive trace or substrate under 5A of current for 2 minutes, heating to a maximum recorded temperature of 76.3℃. Several multifunctional components were fabricated as case studies to further validate the process. Several small passive electronic devices (e.g., a heater and an interdigitated capacitor) are fabricated to demonstrate selective deposition of complex copper traces. The fabrication of an Archimedes spiral on a hemispherical substrate via Cu-LIG is completed to demonstrate the ability to use the process to fabricate conformal conductive traces. An LED circuit is fabricated on a face-center cubic AM-PI lattice which demonstrates multi-planar fabrication on geometrically complex 3D printed substrates.

By amplifying millions or billions of copies of a DNA’s specific segment, polymerase chain reaction (PCR) has a wide range of applications in DNA cloning, forensics, medical, and infectious disease detection. As a result, the technology is becoming more and more widespread as the COVID-19 pandemic pushes for the need for rapid nucleic acid testing, and for early diagnosis compared to antigens testing. This research aims to develop a laser induced graphene (LIG) heater as the heating element for PCR point-of-care testing (POCT), as the PCR detection result is highly dependent on following a specific reagent heating cycle. In particular, the LIG heater can be integrated directly on a polymeric film by laser scribing in one step, eliminating the need for photolithography or chemical vapor deposition, and the entire device can be fabricated in under 5 minutes. This work investigates the heating performance of the LIG heater, by both Ansys Fluent simulation and actual experimentations. To efficiently control the thermal cycling, a LabVIEW program is constructed to obtain the voltage, temperature, and electrical current of the device, and it is highly adjustable to obtain the maximum heat ramp rate of 11.2 °C/s, and cooling rate of 10.8 °C/s in ambient condition. As a result, the thermocycler requires approximately 510 mW to maintain at 95 °C, with an accuracy of ±0.18 °C. Moreover, the device has shown high stability after 24 hours of repeated thermal cycling, with the average power consumption goes from 365 mW to 368 mW. With low power consumption and rapid fabrication, LIG shows great potential not only for PCR heating elements but also for chemical, gas sensors, flexible electronics, and various other applications.