Dissolvable smartwatch makes for easier electronics recycling

Date:
August 4, 2021
Source:
American Chemical Society
Summary:
Small electronics, including smartwatches and fitness trackers,
aren't easily dismantled and recycled. So when a new model
comes out, most users send the old devices into hazardous waste
streams. To simplify small electronics recycling, researchers have
developed a two-metal nanocomposite for circuits that disintegrates
when submerged in water.

They demonstrated the circuits in a prototype transient device --
a functional smartwatch that dissolved within 40 hours.



FULL STORY ========================================================================== Small electronics, including smartwatches and fitness trackers, aren't
easily dismantled and recycled. So when a new model comes out, most users
send the old devices into hazardous waste streams. To simplify small electronics recycling, researchers reporting in ACS Applied Materials & Interfaces have developed a two-metal nanocomposite for circuits that disintegrates when submerged in water. They demonstrated the circuits in
a prototype transient device -- a functional smartwatch that dissolved
within 40 hours.


========================================================================== Planned obsolescence and the fast pace of technology innovations leads to
new devices that are continuously replacing old versions, which generates millions of tons of electronic waste per year. Recycling can reduce the
volume of e- waste and is mandatory in many places. However, it often
isn't worth the effort to recycle small consumer electronics because their parts must be salvaged by hand, and some processing steps, such as open
burning and acid leaching, can cause health issues and environmental
pollution. Dissolvable devices that break apart on demand could solve
both of those problems. Previously Xian Huang and colleagues developed
a zinc-based nanocomposite that dissolved in water for use in temporary circuits, but it wasn't conductive enough for consumer electronics. So,
they wanted to improve their dissolvable nanocomposite's electrical
properties while also creating circuits robust enough to withstand
everyday use.

The researchers modified the zinc-based nanocomposite by adding silver nanowires, making it highly conductive. Then, they screen-printed the
metallic solution onto pieces of poly(vinyl alcohol) -- a polymer
that degrades in water -- and solidified the circuits by applying
small droplets of water that facilitate chemical reactions and then
evaporate. With this approach, the team made a smartwatch with multiple nanocomposite-printed circuit boards inside a 3D printed poly(vinyl
alcohol) case. The smartwatch had sensors that accurately measured a
person's heart rate, blood oxygen levels and step count, and sent the information to a cellphone app via a Bluetooth connection. The outer
package held up to sweat, but once the whole device was fully immersed
in water, both the polymer case and circuits dissolved completely within
40 hours.

All that was left behind were the watch's components, such as an
organic light- emitting diode (OLED) screen and microcontroller,
as well as resistors and capacitors that had been integrated into the
circuits. The researchers say the two-metal nanocomposite can be used to produce transient devices with performance matching that of commercial
models, which could go a long way toward solving the challenges of small electronics waste.

The authors do not acknowledge a funding source for this study.

========================================================================== Story Source: Materials provided by American_Chemical_Society. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. Jiameng Li, Jiayin Liu, Wangwei Lu, Ziyue Wu, Jingxian Yu,
Bangbang Wang,
Zhe Ma, Wenxing Huo, Xian Huang. Water-Sintered Transient
Nanocomposites Used as Electrical Interconnects for Dissolvable
Consumer Electronics.

ACS Applied Materials & Interfaces, 2021; 13 (27): 32136 DOI:
10.1021/ acsami.1c07102 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/08/210804123515.htm

--- up 12 weeks, 5 days, 22 hours, 45 minutes
* Origin: -=> Castle Rock BBS <=- Now Husky HPT Powered! (1:317/3)