Liquid metal synthesis for better piezoelectrics: Atomically-thin tin- monosulfide
Potential materials for future wearable electronics and other motion-
powered, energy-harvesting devices

Date:
July 10, 2020
Source:
ARC Centre of Excellence in Future Low-Energy Electronics
Technologies
Summary:
Scientists have applied liquid-metal synthesis to piezoelectrics,
advancing future flexible, wearable electronics, and biosensors
drawing their power from the body's movements. Piezoelectric
materials such as atomically-thin tin-monosulfide (SnS) convert
mechanical forces or movement into electrical energy. Along with
their inherent flexibility, this makes them candidates for flexible
nanogenerators in wearable electronics or internal, self-powered
biosensors.



FULL STORY ========================================================================== RMIT-UNSW collaboration applies liquid-metal synthesis to piezoelectrics, advancing future flexible, wearable electronics, and biosensors drawing
their power from the body's movements.


========================================================================== Materials such as atomically-thin tin-monosulfide (SnS) are predicted
to exhibit strong piezoelectric properties, converting mechanical forces
or movement into electrical energy.

This property, along with their inherent flexibility, makes them likely candidates for developing flexible nanogenerators that could be used in wearable electronics or internal, self-powered biosensors.

However to date, this potential has been held back by limitations in synthesising large, highly crystalline monolayer tin-monosulfide (and
other group IV monochalcogenides), with difficulties caused by strong interlayer coupling.

The new study resolves this issue by applying a new liquid-metal
technique, developed at RMIT, to synthesise the materials.

Subsequent measurements confirm that tin-monosulfide synthesised using
the new method displays excellent electronic and piezoelectric properties.



==========================================================================
The resulting stable, flexible monolayer tin-monosulfide can be
incorporated in a variety of devices for efficient energy harvesting.

The work started over two and a half years ago and strong collaborative
work between RMIT and UNSW allowed its fruition. Ms Hareem Khan, the
first author of the paper, showed remarkable perseverance to surmount
many technical challenges to demonstrate the viability of the concept,
with Prof Yongxiang Li.

LIQUID METAL SYNTHESIS The unprecedented technique of synthesis used
involves the van der Waals exfoliation of a tin sulphide (SnS), that is
formed on the surface of tin when it is melted, while being exposed to
the ambient of hydrogen sulfide (H2S) gas.

H2S breaks down on the interface and sulfurises the surface of the melt
to form SnS.

The technique is equally applicable to other monolayer group IV monochalcogenide, which are predicted to exhibit the same strong piezoelectricity.



==========================================================================
This liquid metal based method allows us to extract homogenous and large
scale monolayers of SnS with minimal grain boundaries.

Measurements confirm the material has high carrier mobility and
piezoelectric coefficient, which translates into exceptional peak values
of generated voltage and loading power for a particular applied strain, impressively higher than that any previously reported 2D nanogenerator.

High durability and flexibility of the devices are also demonstrated.

This is evidence that the very stable as-synthesised monolayer SnS can
be commercially implemented into power-generating nanodevices.

They can also be used for developing transducers for harvesting mechanical human movements, in accordance to the current technological inclinations towards smart, portable and flexible electronics.

The results are a step towards piezoelectric-based, flexible, wearable
energy- scavenging devices.

It also presents an unprecedented synthesis technique for large (wafer)
scale tin-monosulfide monolayers.

PIEZOELECTRIC MATERIALS Piezoelectric materials can convert applied
mechanical force or strain into electrical energy.

Best known by name in the simple 'piezo' lighter used for gas BBQs and stovetops, piezo-electric devices sensing sudden changes in acceleration
are used to trigger vehicle air bags, and more-sensitive devices recognise orientation changes in mobile phones, or form the basis of sound and
pressure sensors.

Even more sensitive piezoelectric materials can take advantage of the
small voltages generated by extremely small mechanical displacement,
vibration, bending or stretching to power miniaturised devices, for
example biosensors embedded in the human body, removing the need for an external power source.


========================================================================== Story Source: Materials provided by ARC_Centre_of_Excellence_in_Future_Low-Energy_Electronics
Technologies. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Hareem Khan, Nasir Mahmood, Ali Zavabeti, Aaron Elbourne, Md. Ataur
Rahman, Bao Yue Zhang, Vaishnavi Krishnamurthi, Paul Atkin,
Mohammad B.

Ghasemian, Jiong Yang, Guolin Zheng, Anil R. Ravindran, Sumeet
Walia, Lan Wang, Salvy P. Russo, Torben Daeneke, Yongxiang Li,
Kourosh Kalantar- Zadeh. Liquid metal-based synthesis of high
performance monolayer SnS piezoelectric nanogenerators. Nature
Communications, 2020; 11 (1) DOI: 10.1038/s41467-020-17296-0 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/07/200710100930.htm

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