RL

I

VL+

-ZnO

First proposed and practiced the Principle of nanogenerator using ZnO nanowires

• By deflecting the aligned ZnOnanowires (NWs) grown on a polymer substrate using a conductive atomic force microscopy (AFM) tip in contact mode, the energy that was first created by the deflection force and later converted into electricity by piezoelectric effect has been measured for demonstrating nano-scale power generator.

• The approach presented has the potential of converting biological mechanical energy, acoustic/ultrasonic vibration energy, and biofluid hydraulic energy, into electricity, demonstrating a new path way for self-powering of wireless nanodevices and nanosystems.

Landmark publications:

Science, 312 (2006) 242.Nano Letters, 3 (2004) 423-426

First invented DC nanogenerator driven by ultrasonic wave

Wang et al., Science 316 (2007) 102-105

• Having replaced the use of an expensive and sophisticated AFM by ultrasonic wave/vibration for inducing the elastic deformation and vibration of the NWs, and demonstrated a cost-effective prototype technology for fabricating the nanogenerator;

• Having achieved a continuous and fairly stable DC output.

• The DC nanogenerator works in air and in liquid

• The principle demonstrated can be further optimized and improved for enhancing output power, establishing a basic method for harvesting/recycling energy from the environment, such as body movement, mechanical vibration, and sonic waves….

• The concept and prototype technology established by the DC nanogenerator set a platform for developing self-powering nanosystems with important applications in implantable in-vivo biosensing, wireless and remote sensing, nanorobotics, MEMS, sonic wave detection and more

ZnOnanowires

ZnO layerSupporting substrate

vibrating

W nanowires

Metal substrate

First Invented Textile fiber based nanogenerators• Using ZnO NWs grown on fibers, it is possible to

fabricate flexible, foldable and wearable power source in any shape (such as “power shirt”).

• The nanogenerator operates at (< 10 Hz) in the range of conventional mechanical vibration, foot steps and heart beating, greatly expanding the application range of nanogenerators.

Qin, Wang, WangNature 451 (2008) 809

Piezoelectric Nanogenerator – potential applications

Bending piezoelectric ZnO nanowire (NW) generates electrical potential along side surfaces

To deflect many NWs simultaneously for continuous output

Vertical aligned ZnO NW arrays

Zigzag silicon trench coated with platinum

Integrate with spacing control

Zigzag electrode

ZnO nanowires•Mechanical vibration triggers the bending of NWs;

•Piezoelectric potential collects by the trenches.

Mechanical energy sources

Wind

Wave

Blood flow & heart beating

Breath

Car running

Air conditioning

Body movements

Xudong Wang, et al., Science, 316 (2007) 102.

Biomedicine

MEMs & Nanodevices

Defense technology

Wireless sensors

Robots

Personal electronics

MP3sCell phones

Laptops

Nanosensors

MEMs

Nanogenerator converts mechanical waves into electricity

Implantable devices

+ + + + + +

- - - - - --

Vp+

Vp-

VF

- - -

PE-diode

VSD

VG

- - - -+ + + +

SiliconGate oxide

FET

VSD

VG

- - - -+ + + +

Silicon

Trapped carriers

+ + + + + +

- - - - - --

Vp+

Vp-

V

F

- - -

PE-FET

z

a Ez

Ez>0

Ez<0

Ez=0

c

Vp>0 (Vp )

Vp<0 (Vp )

Vp=0

+

-

dεz

ε>0

ε<0

ε=0

bF

Founder of Nano-Piezotronics

Materials Today, 10 (2007) 20-28;Adv. Mater., 19 (2007) 889-992

Nano Letters, 6 (2006) 2768-2772

Nano-PiezotronicsPiezoelectricity is the ability of certain crystals to generate a voltage in response to

applied mechanical stress. Electronics - the branch of physics that deals with the emission and effects of electrons

and with the use of electronic devices.

Piezotronics is a field of using piezoelectric-semiconducting coupled properties/effects for creating/fabricating novel and unique electronic devices and components (ZLW).

Piezoelectric-field effect transistor Piezoelectric-gated diode

V~Pt

ZnO Nanobelt

200 210 220 230 240 250 260 270 281 291 301 311

246.81MHz

270.44MHz

Frequency (MHz)

1st Harmonic

V~Pt

ZnO Nanobelt

V~V~Pt

ZnO Nanobelt

200 210 220 230 240 250 260 270 281 291 301 311

246.81MHz

270.44MHz

Frequency (MHz)

1st Harmonic

200 210 220 230 240 250 260 270 281 291 301 311

246.81MHz

270.44MHz

Frequency (MHz)

1st Harmonic

Piezoelectric resonator

Piezoelectric nanogenerator Piezoelectric FET sensors

DC nanogenerator

10 μm

(a) (c)

Morpho Peleides

Bio-interfacing, bio-inspired fabrication and bioengineering

Nano Letters, 6 (2006) 2325

350 450 550 650 750 850

30º

Incident light

Reflected light

Silicon substrate

60º

Wavelength (nm)

Ref

lect

ance

(a.u

.)

Tape on silicon substrate

Natural butterfly wing

605 nm alumina coated butterfly wing

Alumina replica

420 nm

390 nm

1 cm

Gecko foot

Tokay Gecko

(Autumn, 2000)

Nano-piezotronics;

Bio-interfacing, bio-inspired fabrication and bioengineering;

Solar energy;

Nanogenerators for harvesting mechanical energy; self-powered nanosystems

Microscopy and functional nanomaterials

BaMnO3 nanobelts

Near Future Research Directions