Shellac-paper composite as a green substrate for printed electronics

Abstract

Printed electronic devices that sense and communicate data will become ubiquitous as the Internet of Things continues to grow. Devices that are low cost and disposable will revolutionize areas such as smart packaging, but a major challenge in this field is the reliance on plastic substrates such as polyethylene terephthalate. Plastics discarded in landfills degrade to form micro- and nanoplastics that are hazardous to humans, animals, and aquatic systems. Replacing plastics with paper substrates is a greener approach due to the biodegradability, recyclability, low cost, and compatibility with roll-to-roll printing. However, the porous microstructure of paper promotes the wicking of functional inks, which adversely affects printability and electrical performance. Furthermore, truly sustainable printed electronics must support the separation of electronic materials, particularly metallic inks, from the paper substrate at the end of life. This important step is necessary to avoid contamination of recycled paper and/or waste streams and enable the recovery of electronic materials. Here, we describe the use of shellac – a green and sustainable material – as a multifunctional component of green, paper-based printed electronics. Shellac is a cost-effective biopolymer widely used as a protective coating due to its beneficial properties (hardness, UV resistance, and high moisture- and gas-barrier properties); nonetheless, shellac has not been significantly explored in printed electronics. We show that shellac has great potential in green printed electronics by using it to coat paper substrates to create planarized, printable surfaces. At the end of life, shellac acts as a sacrificial layer. Immersing the printed device in methanol dissolves the shellac layer, enabling the separation of printed electronic materials from the paper substrate.

Towards fully green printed device with environmental perspectives

“…Figures 3(b) and (c) show the slight decrease in the contact angle of the drop of deionized water, indicating the trend of increasing hydrophilicity with added shellac layers. This observation corresponds to work [19], where with the additional shellac layer contact angle decreased. It was also observed that the addition of shellac layers strongly influenced the roughness of the surface.…”

“…A 200 mg ml −1 shellac solution was prepared by dissolving 800 g of Kusmi seedlac in 4 liters of anhydrous ethanol by agitating the mixture for 90 min at 150 rpm using an orbital shaker [19]. The mixture was subsequently allowed to rest for 24 h to permit the wax and other debris to settle.…”

“…Among its applications, it can be used as a protective layer over the printed conductive and insulating materials, to improve the durability and stability of the device [18]. For example, Hussein et al [19] has combined the shellac with paper substrates through a dip-coating process to provide composites with planarized and compatible surfaces.…”

A Green Conformable Thermoformed Printed Circuit Board Sourced from Renewable Materials

“…Cellulose-based materials have been proposed so far in various works as green PCB substrates. Cellulose and nanocellulose substrates have many advantages, such as flexibility, biodegradability, recyclability, and low cost, − but they suffer high roughness, moisture sensitivity, and poor barrier properties, all significant drawbacks in electronics, where smooth and humidity-insensitive substrates are required . Another approach to make green PCBs relies on including waste from the agricultural and farming sector such as lignin, rice husks, banana fibers, and chicken feather fibers, at high percentages reaching even more than 50% by weight, inside an epoxy resin. − Nevertheless, epoxy resin is still present as binder in those substrates with all of the end-of-life issues previously described.…”

Impact of ink deposition and trace path variations on 3D-printed antenna performance

“…3 Prior research delved into the realm of 3D printing techniques for fabricating electrical traces. 4,5 These investigations have ventured into diverse materials 6 and patterns, 7 leveraging ink-jet printing to create intricate electrical pathways. Within this body of work, however, a conspicuous research gap exists: a comprehensive understanding of how ink deposition and variations in trace paths impact the frequency and amplitude of the 3Dprinted antennas remains elusive.…”