Page 33 - october22_previewaa.indd
P. 33
TAP TIMES -33- OCTOBER 2022
Biodegradable PC board (from 32) for seven months. After pulling the cir-
cuit from storage, the researchers applied
the end of a polymer chain. By control- continuous electrical voltage to the device
ling when the lipase finds the chain end, for a month and found that the circuit
it is possible to ensure the materials don’t conducted electricity just as well as it did
degrade until the water reaches a certain before storage.
temperature.
Immersed in warm water
Shelf-ready BC lipase “cocktails” Next, the researchers put the device’s re-
For the current study, Xu and her team cyclability to test by immersing it in warm
simplified the process even further. In- water.
stead of expensive purified enzymes, the
biodegradable printed circuits rely on Within 72 hours, the circuit materials de-
cheaper, shelf-ready BC lipase “cocktails.” graded into its constituent parts — The
silver particles completely separated from
the polymer binders, and the polymers
This significantly reduces costs, facilitating broke down into reusable monomers, al-
the printed circuit’s entry into mass manu- lowing the researchers to easily recover
facturing, Xu said. the metals without additional processing.
By doing so, the researchers advanced By the end of this experiment, they de-
the technology, enabling them to develop termined that approximately 94% of the
a printable “conductive ink” composed of silver particles can be recycled and reused
biodegradable polyester binders, conduc- with similar device performance.
tive fillers such as silver flakes or carbon
black, and commercially available enzyme That the circuit’s degradability continued
cocktails. after 30 days of operation surprised the
researchers, suggesting that the enzymes
Electrically conducive ink were still active.
The ink gets its electrical conductivity from
the silver or carbon black particles, and “We were surprised”
the biodegradable polyester binders act as “We were surprised that the enzymes
a glue. ‘lived’ for so long. Enzymes aren’t de-
signed to work in an electric field,” Xu
The researchers supplied a commercial 3D said.
printer with the conductive ink to print cir-
cuit patterns onto various surfaces such as Xu attributes the working enzymes’ lon-
hard biodegradable plastic, flexible biode- gevity to the biodegradable plastic’s mo-
gradable plastic, and cloth. lecular structure.
In their previous study, the researchers
This proved that the ink adheres to a vari- learned that adding an enzyme protec-
ety of materials, and forms an integrated tant called random heteropolymer, or RHP,
device once the ink dries. To test its shelf helps to disperse the enzymes within the
life and durability, the researchers stored a mixture in clusters a few nanometers (bil-
printed circuit in a laboratory drawer with- lionths of a meter) in size.
out controlled humidity or temperature next page
