We introduce E-LIG, a laser-enabled, additive fabrication method for flexible, double-sided printed circuit boards (PCBs) with integrated functional devices. E-LIG combines laser-induced graphene (LIG) patterning with copper electroplating to create high-resolution circuits directly on flexible and transparent substrates. We demonstrate circuits with embedded sensors and actuators on a single substrate, showing the method’s scalability, and suitability for applications in wearables, soft robotics, and interactive surfaces.
Abstract
The demand for flexible and printed electronics in wearable and soft robotics applications has increased the need for scalable, additive manufacturing processes. However, traditional printed circuit board manufacturing involves complex, multistep processes, is limited to certain substrates, and faces challenges in integrating functional devices. Here, an additive, laser-enabled process is introduced for fabricating flexible, double-sided printed electronics leveraging laser-induced graphene (LIG) as a seed layer for selective copper electrodeposition (E-LIG). This technique enables precise conductive circuit patterning down to 50 µm and is reliable via formation in a single streamlined process. E-LIG supports transfer to various substrates, allowing for large-area electronics up to 100 cm2, broadening applications in large-scale interfaces. Functional LIG device integration, including sensors and actuators, directly interfaced with control circuits on a single substrate is demonstrated. Applications such as real-time graphical output and interactive interfacing showcase the method's versatility. E-LIG exhibits repairability for on-demand restoration of damaged circuits, enhancing durability and offering a scalable, cost-effective solution for multifunctional printed electronics.
Laser-Enabled Circuit Patterning
Using a CO2 laser, the desired circuit pattern can be etched onto a sheet of polyimide (PI) and electroplated to form E-LIG. SMD components are then placed onto the copper-plated circuit with conventional reflow soldering, and the finished PCB is coated with a protective layer of transparent polymer (PDMS).
Double-Sided Flexible Circuits
The same process of forming E-LIG can be applied to both sides of the same sheet of PI, thus allowing the formation of double-sided PCBs. Using a higher power and speed for the CO2 laser, a small hole can be created, and this produces a thin layer of LIG along the via wall which will then be copper-electroplated along with the traces on both sides of the PI.
Transparent and Flexible Substrates
Once electroplated and populated, an E-LIG circuit can be fully transferred to a transparent substrate like PDMS and maintain its flexibility.
Seamless Integration: Embedded Devices
Devices like sensors and actuators can be lasered onto the same substrate as the circuit. They can then be selectively coated with polymers like PDMS to avoid being copper-plated, thus forming a seamless integration of LIG devices to flexible PCBs.