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Prototypes

In terms of prototype devices, recent work from our group

2

on

polymer-based nanogenerators has resulted in significant

advances in the field, notably the development of scalable ‘self-

poled’ nanogenerators based on piezoelectric polymer nanowires

grown by a simple and versatile template-wetting fabrication

method. This cost-effective technique is well suited for large scale

production and results in nanowires with high energy conversion

efficiency.We

demonstrated a small prototype nanogenerator that

produces an electrical output when lightly

tapped.We

showed that

this outputted electrical energy can be stored in a bank of

capacitors and then used to light a commercial LED.

While there have been several reports in the literature on

nanogenerators based on both piezoelectric ceramic and

polymer nanowires, key performance parameters such as

mechanical-to-electrical conversion efficiency and frequency

dependence have been largely unreported, making it impossible

to compare materials performance for practical applications. We

have recently defined novel and bespoke figures of merit with

the aim of catalysing a more focused and meaningful

discussion of these promising materials and devices, thus

enabling the field to mature.

3

Our analysis is straightforward and covers all realisable

nanogenerator-driving mechanisms, enabling a rigorous

quantitative comparison between nanogenerator materials that

has been hitherto absent in this highly technologically relevant

field.We

investigated, in detail, the energy harvesting performance

of prototypical piezoelectric ceramic and polymer nanowires. Our

studies revealed that even though ceramic and polymer nanowires

have been found, in certain cases, to have similar energy

conversion efficiencies, ceramics are more promising in ‘strain-

driven’ nanogenerators, while polymers are more promising for

‘stress-driven’ nanogenerators. Our approach therefore highlights

the differences in the energy harvesting performance of

piezoelectric polymer and ceramic nanowires under different

driving conditions, revealing that these two material classes

present orthogonal opportunities which, while important, have not

been elucidated before. As nanogenerators begin to make the

transition from the lab to the real world, our work offers a timely

and highly relevant benchmark by which piezoelectric materials

and nanogenerator geometries can be designed and/or

engineered for specific applications.

ERC starting grant - NANOGEN

With the recent award of an ERC starting grant on ‘Polymer-based

piezoelectric nanogenerators for energy harvesting’ (NANOGEN), I

aim to cement my position as a leader in the global energy

harvesting community, with a world class research group that can

impact the way smart technology interfaces with our lives in the

future. In fact, the impact of this research goes well beyond energy

harvesting as piezoelectric nanowires are extremely strain

sensitive and can function as self-powered sensors.

In this context, polymer-based piezoelectric nanogenerators, as

power sources for ‘reporting devices’, have applications in

transportation, healthcare management, smart cities and for the

community at large through passive reporting via wireless sensor

networks or the IoT. Additionally, piezoelectric nanowires are

particularly robust and can be stimulated by tiny physical

motions/disturbances over a large frequency range, thus

presenting the opportunity for a new class of strain-sensitive

devices for active reporting on critical elements. The polymer-

based nanowires developed over the course of the starting grant

will therefore be attractive for applications ranging from

monitoring vital signs, early fault detection systems in buildings,

and critical element reporting in aerospace applications to

piconewton-scale force sensing in biological systems.

References

1

S Crossley, R A Whiter & S Kar-Narayan (2014): Polymer-based nano-

piezoelectric generators for energy harvesting applications,

Materials Science

and Technology

30, 1613

2

R A Whiter,V Narayan & S Kar-Narayan (2014): A scalable nanogenerator

based on piezoelectric polymer nanowires with high energy conversion

efficiency,

Advanced Energy Materials

4, 1400519

3

S Crossley & S Kar-Narayan (in press 2015): Energy Harvesting Performance of

Piezoelectric Ceramic and Polymer Nanowires,

Nanotechnology

Sohini Kar-Narayan

University Lecturer

Department of Materials Science

University of Cambridge

tel :

+44 (0)1223 331695

sk568@cam.ac.uk http://people.ds.cam.ac.uk/sk568 www.horizon2020projects.com

H O R I Z O N 2 0 2 0 P R O J E C T S : P O R TA L

I S S U E S E V E N

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P R O F I L E

S P E C I A L F E AT U R E : M AT E R I A L S

Prototype energy harvesting device based on piezoelectric

polymer nanowires