Two-dimensional Rotary Triboelectric

7232019 Two-dimensional Rotary Triboelectric

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RAPID COMMUNICATION

Two-dimensional rotary triboelectric

nanogenerator as a portable and wearable

power source for electronics

Shuang Yang Kuanga Jun Chenb Xiao Bei Chenga Guang Zhuan

Zhong Lin Wangab

aBeijing Institute of Nanoenergy and Nanosystems Chinese Academy of Sciences Beijing 100083 ChinabSchool of Materials Science and Engineering Georgia Institute of Technology Atlanta GA 30332 USA

Received 14 May 2015 received in revised form 17 June 2015 accepted 9 July 2015

Available online 5 August 2015

KEYWORDSEnergy harvestingTriboelectric nano-

generatorSelf-poweredWearable electronics

Abstract

Harvesting energy from ambient mechanical motions addresses limitations of traditional power

supplies by providing a sustained electric power source Here a high-performance rotary

triboelectric nanogenerator (r-TENG) is applied in a variety of circumstances to speci1047297callyharvest mechanical energy from human body motions When rotating at 500 r min1 it can

produce an ac electric output that has a current amplitude of 075 mA and a voltage amplitude

of 200 V at a frequency of 750 Hz Integrated with structural components that transfer

mechanical motions and electric components that achieve power management the r-TENG is

demonstrated as a power source by harvesting energy from foot pedaling arm swinging and

foot pressure The generated electricity can effectively charge consumer electronics such as a

cellphone which shows the promise of the r-TENG as a power source for portable wearable

and even implantable electronics

amp 2015 Elsevier Ltd All rights reserved

Introduction

The fast development of portable electronics requires a stand-

alone maintenance-free and sustainable power source

Harvesting and converting ambient energy provides a feasible

solution for this purpose Mechanical motion is an attractive

target for energy harvesting due to its great abundance and

ubiquitousness [1ndash6] Current mechanical energy harvesting

technologies are mainly relying on mechanisms including

electromagnetic effect piezoelectric effect and electrostatic

induction [17ndash9] However major challenges are still to be

addressed including low output power structure complexity

httpdxdoiorg101016jnanoen201507011

2211-2855amp 2015 Elsevier Ltd All rights reserved

nCorresponding author

E-mail address zhuguangbinncascn (G Zhu)

Nano Energy (2015) 17 10ndash16



and dif 1047297culty in miniaturization [10ndash16] In recent years

triboelectric nanogenerators (TENG) that had a novel mechan-

ism were developed It is especially suitable as a portable

power source that harvests energy from body motions due to

its prominent advantages of high power density in terms of

power per volume as well as power per weight [11718]

Although various structures of TENGs have been developed

[1719ndash23] high-performance TENGs that are speci1047297cally

designed for harvesting energy from body motions and can

provide useful amount of output power were rarely reported

Here we report a series of solutions for practically poweringand charging portable electronics by harvesting energy from

body motions including foot pedaling hand swinging and foot

pressure These approaches are all based on high-performance

two-dimensional rotary TENGs (r-TENG) Enabled by a design of

two radial-arrayed 1047297ne electrodes that are complementary on

the same plane the planar-structured r-TENG produces peri-

odically changing triboelectric potential that induces alternat-

ing currents between electrodes At a rotating rate of

500 r min1 it can deliver a continuous ac output that has a

short-circuit current of 075 mA in amplitude and an open-

circuit voltage of 200 V at a frequency of 750 Hz By integrating

the r-TENG with other mechanical components it can effec-

tively utilize motions from different parts of human body When

installed onto a bicycle the r-TENG can convert mechanical

energy of foot pedaling into electricity powering an array of

small electronics as well as charging a cellphone Besides it can

harness energy from arm swinging as well as foot pressing

during normal walking Through a power management circuit

the electric output can be used to charge capacitors and

batteries unambiguously demonstrating the r-TENG as a pro-

mising power source for portable wearable and even poten-

tially implantable electronics

Results and discussions

A r-TENG is composed of mainly two parts a stator and a

rotator as depicted in Figure 1a The rotator is a collection

of 90 radially-arrayed sectors made of copper For the

stator it is composed of mainly three parts a layer of

polymethyl methacrylate (PMMA) as a substrate a layer of

electrodes and a layer of polytetra1047298uoroethylene (PTFE) as

an electri1047297cation layer The electrode layer is composed of

electrode A and electrode B which have complementary

patterns separated by 1047297ne gaps in between as shown in the

zoom-in sketches of the inner and outer sections of the

stator in Figure 1a As photographed in Figure 1b and c both

Figure 1 Structural design and working principle of the r-TENG (a) Schematic sketches of the r-TENG (b c) Photographs of a rotatorand a stator (scale bar 3 cm) (d) Charge distribution on open-circuit condition (e) Charge distribution on short-circuit condition

11Two-dimensional rotary triboelectric nanogenerator



the rotator and the stator have a two-dimensional planar

structure resulting in small volume of the r-TENG The

detailed fabrication process was previously reported

[1724]

The electricity generation of the r-TENG relies on relative

rotation between the rotator and the stator Cycled change

of electric potential due to the motion of triboelectric

charges gives rise to alternating 1047298ows of electrons between

Figure 2 Electric output of a r-TENG that is 120 mm in diameter (a) Short-circuit current and (b) open-circuit voltage of the

r-TENG (c) Output current after transformation (d) Output voltage after transformation All the results are measured at a constant

rotation rate of 500 r min1

Figure 3 Demonstration of the r-TENG in harvesting energy from pedaling a bicycle (a) Transformed short-circuit current at a rotation

rate of 190 r min1 (b) Transformed open-circuit voltage at a rotation rate of 190 r min1 (c) Photograph showing 60 LEDs are being

lighted up simutanously when the bicyle is being pedaled (scale bar 8 cm) (d) Charging current and (e) charging voltage on the battery of

a cellphone (f) Photograph showing a cellphone is being charged when the bicycle is being pedaled (scale bar 8 cm)

SY Kuang et al12



electrodes The electricity generation process from a single

sector unit is depicted in Figure 1d and e Here two-

dimensional schematic illustrations of the charge distribu-

tion are used for interpretation To begin with when the

rotator rotates coaxially against the stator charge transfer

takes place at the contact interface Negative triboelectric

charges are produced on the PTFE surface since it has a

much stronger tendency to be negatively charged

(Figure 1d) On the open-circuit condition electrons cannot

transfer between electrodes The open-circuit voltage is

then essentially the electric potential difference between

the two electrodes At the initial state when the copper-

made stator is aligned with the left electrode (Figure 1d)

the electric potential of the left and right electrodes is

maximized and minimized respectively which corresponds

to a maximum electric potential difference between the

electrodes When the rotator starts to spin such a potential

difference will diminish to zero when the rotator reaches

the middle point Further rotation will result in a reversely

built-up electric potential difference between the electro-

des as illustrated in the Figure 1d If the two electrodes are

electrically connected namely on the short-circuit condi-tion the induced free electrons can 1047298ow between the

electrodes due to electrostatic induction As the rotator

starts to spin free electrons will keep 1047298owing from the left

electrode to the right electrode until the rotator is in

alignment with the right electrode (Figure 1e) Further

rotation will then generate a current in the opposite

direction

To characterize the electric output of the r-TENG a

programmable motor was employed to provide a mechanical

rotation source at a controlled rate At a rotating rate of

500 r min1 the short-circuit current (Isc) of the r-TENG has

a continuous ac manner at an amplitude of 075 mA and a

frequency of 750 Hz The open-circuit voltage (V oc) exhibits

a peak-to-peak value of 400 V at the same frequency In

order to realize impedance match between the TENG that

has high output impedance and conventional electronics

that are known for low input impedance we transformed

the electric output to enhance the output current at the

expense of the output voltage As shown in Figure 2c and d

the current amplitude is greatly boosted to about 16 mA

while the output voltage drops to about 32 V By doing so

the impedance match ensures that the maximum amount of

electric output can be extracted from the TENG for

practical use

To demonstrate practical applications we designed and

fabricated three types of devices that are based on the r-

TENG First we installed a r-TENG that is 150 mm in

diameter on the wheel axis of a 1047297tness bicycle When being

pedaled the relative rotation between the rotator and the

stator generates high-level electric output As shown in the

Figure 3a and b at a rotation rate of about 183 r min1 the

current amplitude after being tuned by transformers

reaches as high as 13 mA and the voltage amplitude

exceeds 36 V When directly using the generated electricitywe could simultaneously power over 20 LED lamps (12 V

06 W for each) which is demonstrated in Figure 3c and

Supplementary Movie S1 Besides powering small electro-

nics the electric output could be used to charge electro-

nics Here besides transformers we added recti1047297ers

capacitors and voltage regulators to construct a power

management circuit that can provide an output voltage at

a preset value (diagramed in Supplementary Figure S1)

When being plugged into a cellphone a charging system

consisting of the r-TENG and the power management circuit

can effectively charge a battery When being triggered by

pedaling the charging current shoots to 13 mA (Figure 3d)

Figure 4 Demonstration of the r-TENG for harvesting energy from human arm swinging (a) Schematic of the entire device (b) Diagram

of the device when the arm is stretched (c) Diagram of the device when the arm is bent (d) Short-circuit current and (e) open-circuitvoltage of the r-TENG at a swing frequency of 5 Hz (f) Transformed and recti1047297ed current On the right is an enlarged view of the current

signal (g) Photograph showing about 60 LEDs being lighted up simutaneously when the r-TENG is being swung (scale bar 10 cm)

(h) Charging curve of a capacitor with a capacitance of 4700 μF Inset is the diagram of a power management circuit




and the charging voltage 1047298uctuates around 7 V (Figure 3e)

The charging sign was immediately displayed on the cell-

phone screen as shown in Figure 3f and Supplementary

Movie S2

Supplementary material related to this article can be

found online at doi101016jnanoen201507011Second a wearable device for harvesting energy from

human body motion was demonstrated As shown in

Figure 4a the entire device mainly consists of three parts

a base a teethed rack and a r-TENG that is 10 mm in

diameter The r-TENG is attached to the upper arm while

the base is 1047297xed to the front arm around the wrist When

the arm is being swung a rotary torque is generated and

transferred to the r-TENG through the teethed rack and a

gear (Figure 4b and c) As a result the rotator is driven At a

swinging frequency of around 3 Hz the measured Isc(Figure 4d) and the V oc (Figure 4e) have amplitudes of up

to 025 mA and 120 V respectively For a single swinging

motion the instantaneous rotation rate varies and reaches

its peak value midway through the swinging Consequently

the obtained current pack in Figure 3f has the largest

amplitude in the middle However the voltage amplitude

in Figure 4e remains stable since it is velocity-independent

After being recti1047297ed and transformed the output currentbecomes unidirectional and reaches a peak value of 16 mA

The 1047298uctuating dc output in Figure 4g could not only

directly power a LED array (Figure 4h and Supplementary

Movie S3) but also charge a capacitor to have the energy

stored

Furthermore we speci1047297cally designed a device for har-

vesting energy from the foot pressure during normal walk-

ing The entire device is displayed in Figure 5 It has a

dimension of 6 cm by 6 cm by 3 cm Within in the device

two r-TENGs are stacked together in the vertical direction

As sketched in Figure 5b the two rotators share the same

substrate and rotate simultaneously The rotation is

Figure 5 Demonstration of the r-TENG for harvesting energy from foot pressure (a) Photograph of the entire device (b) Sketch

that illustrates the motions transmission component It transforms linear motion to rotation (c) Photograph showing an enlarged

view of the helical axis (d) Photograph showing an enlarged view of two r-TENGs that are stacked together (e) Transformed voltage

of the upper unit r-TENG On the right is an enlarged view of output voltage signal (f) Transformed voltage of the lower unit r-TENG

at a uniform walking rate On the right is an enlarged view of output voltage signal (g) Transformed and recti1047297ed current from the

two r-TENGs On the right is an enlarged view of output current signal (h) Charging curve of a battery with a capacity of 7 mA h

Inset is the corresponding diagram of a charging circuit

SY Kuang et al14



triggered by a helical axis in the vertical direction

(Figure 5c) When the helical axis is pressed down it exerts

a rotation torque to the rotator in the clockwise direction

due to its helical structure As a result the liner motion of

the axis is transformed to lateral rotation of the r-TENG It

was found that our design could enable a quarter of circular

rotation provided with a linear motion of 6 mm After

electric transformation the measured output voltage from

the upper r-TENG is shown in Figure 5e There are two

voltage packs in a one cycle This is because rotation in the

counterclockwise direction occurs after the pressing force is

withdrawn because the four springs in the device (Figure 5a)

provides a restoring force It is also noticed that the

releasing process corresponds to higher electric output from

the upper unit which is attributed to the damping effect of

a soft cushion-like structure in the device In contrast the

transformed output voltage from the lower unit exhibits

higher amplitude for the pressing process After further

recti1047297cation and integration the combined output current

from the two r-TENGs has comparable amplitudes for both

pressing and releasing processes as shown in Figure 5g The

amplitude reaches around 5 mA which could charge alithium ion battery of 6 mA h in capacity from 25 V to

32 V in 10 min when the energy-harvesting device is

triggered at a frequency of 1 Hz

Compare with conventional magnetic generators that also

convert rotational motion into electricity the most promi-

nent advantage of the r-TENG is the high power density

Since the r-TENG relies on triboelectric effect at the

surface it requires very little amount of thin-1047297lm materials

Besides the materials used can be low-density polymers As

a result the r-TENG has exceptionally light weight and

small volume making is particularly suitable as an on-body

power source for portablewearable electronics

Conclusions

To summarize we reported a two-dimensional rotary TENG

Enabled by a design of two radial-arrayed 1047297ne electrodes

that are complementary patterns on the same plane the

planar-structured r-TENG can produce periodically changing

triboelectric potential that induces alternating currents

between electrodes Short-circuit current of 075 mA in

amplitude as well as voltage amplitude of 200 V was

generated at a rotating rate of 500 r min1 The unique

structural design enables various applications First the r-

TENG was 1047297rstly installed onto a bike to harvest energy from

pedaling The generated electricity can be used to charge a

cellphone Second the r-TENG can also be harnessed toharvest energy from arm swinging as well as foot pressure

during walking Through a power management circuit the

transformed output can be used to charge portable electro-

nics which unambiguously demonstrates the TENG as a

sustained power source for small electronics

Acknowledgment

The research was supported by the ldquoThousands Talentsrdquo

Program for Pioneer Researcher and His Innovation Team

China Patents have been 1047297led based on the research

presented here

Appendix A Supplementary Information

Supplementary data associated with this article can be found

in the online version at doi101016jnanoen201507011

References

[1] ZL Wang ACS Nano 7 (2013) 9533[2] X Wang J Song J Liu ZL Wang Science 316 (2007) 102

[3] SP Beeby MJ Tudor NM White Meas Sci Technol 17

(2006) 175

[4] J Scruggs P Jacob Science 323 (2009) 1176

[5] R Henderson Renew Energy 31 (2006) 271

[6] AD Kuo Science 309 (2005) 1686

[7] ZL Wang J Song Science 312 (2006) 242

[8] G Zhu B Peng J Chen Q Jing ZL Wang Nano Energy 14

(2015) 126

[9] ZL Wang J Chen L Lin Energy Environ Sci 8 (2015) 2250

[10] VA Jouanne Mech Eng Mag 128 (2006) 24

[11] S Kwon J Park WK Kim Y Yang E Lee CJ Han SY Park

J Lee YS Kim Energy Environ Sci 7 (2014) 3279

[12] W Huang G Wang F Gao Z Qiao G Wang M Chen

Y Deng L Tao Y Zhao X Fan L Sun J Phys Chem C 118(2014) 8783

[13] T Krupenkin JA Taylor Nat Commun 2 (2011) 448


[15] A Wolfbrandt IEEE Trans Magn 42 (2006) 1812

[16] Z Pi J Zhang C Wen ZB Zhang D Wu Nano Energy 7

(2014) 33

[17] G Zhu J Chen Q Jing T Zhang ZL Wang Nat Commun 5

(2014) 3426

[18] G Zhu Y Zhou P Bai X Meng Q Jing J Chen ZL Wang

Adv Mater 26 (2014) 3788

[19] J Chen J Yang Z Li X Fan Y Zi Q Jing H Guo Z Wen

KC Pradel S Niu ZL Wang ACS Nano 9 (2015) 3324

[20] X Meng G Zhu ZL Wang ACS Appl Mater Interfaces 6

(2014) 8011

[21] J Chen G Zhu J Yang Q Jing P Bai W Yang X Qi Y SuZL Wang ACS Nano 9 (2015) 105

[22] W Seung MK Gupta KY Lee KS Shin JH Lee TY Kim

S Kim J Lin JH Kim SW Kim ACS Nano 9 (2015) 3501

[23] J Chen G Zhu W Yang Q Jing P Bai Y Yang TC Hou Z

L Wang Adv Mater 25 (2013) 6094

[24] C Han C Zhang W Tang X Li ZL Wang Nano Res 8 (2014)

722

Shuang Yang Kuang received his bachelors

degree in Physics in Shandong University

Now he is pursuing his masterrsquos degree in

Beijing Institute of Nanoenergy and Nano-

system Chinese Academy of Science His

current research mainly focuses on applica-

tion and fabrication of triboelectricnanogenerators

Jun Chen received hisBSandMSin Elec-

trical Engineeringfromthe School of Electro-

nic Information and Communications at

HuazhongUniversity of Science and Technol-

ogy in2007 and2010 respectively and a

second MS in Biological Engineering from

the College of Engineering at The University

of Georgia in 2012 HeiscurrentlyaPhD

candidate




intheSchoolofMaterialsScienceand Engineeringat TheGeorgiaInstitu-

teofTechnology Hisresearchfocusesprimarilyonnanomaterial-based

energy harvesting energy storage active sensingand self-powered

micro-nano-systems

Xiao Bei Cheng is a graduate student at the

Chongqing University of Posts and Telecom-

munications He received his Bachelor

degree in Electronic Information Scienceand Technology at Henan Polytechnic Uni-

versity in 2012 His current research mainly

focuses on theenergy conversion and collec-

tion surface tribocharging theory and

power management which improve energy

ef 1047297ciency

Dr Guang Zhu is a professor at Beijing

Institute of Nanoenergy and Nanosystems

Chinese Academy of Sciences He received

his PhD degree in Materials Science and

Engineering at Georgia Tech in 2013 and his

Bachelor degree in Materials Science and

Engineering at Beijing University of Chemi-

cal Technology in 2008 His current research

mainly focuses on designing fabrication

and implementation of innovative miniaturized high-ef 1047297ciency

generators that harvest and convert ambient mechanical energy

into electricity

Dr Zhong Lin Wang is a Hightower Chairand

Regentsrsquo Professor at Georgia Tech Heis

also the Chief scientist and Director forthe

Beijing Institute of Nanoenergy andNanosys-

tems Chinese Academy of SciencesHis dis-covery and breakthroughs in

developingnanogenerators establish the

principleand technological road map forhar-

vesting mechanical energy from environ-

mentaland biological systems for

poweringpersonal electronics He coined andpioneered the 1047297eld of

piezotronics and piezo-phototronics byintroducing piezoelectric

potential gated charge transport processin fabricating new electro-

nic and optoelectronic devices

SY Kuang et al16



and dif 1047297culty in miniaturization [10ndash16] In recent years

triboelectric nanogenerators (TENG) that had a novel mechan-

ism were developed It is especially suitable as a portable

power source that harvests energy from body motions due to

its prominent advantages of high power density in terms of

power per volume as well as power per weight [11718]

Although various structures of TENGs have been developed

[1719ndash23] high-performance TENGs that are speci1047297cally

designed for harvesting energy from body motions and can

provide useful amount of output power were rarely reported

Here we report a series of solutions for practically poweringand charging portable electronics by harvesting energy from

body motions including foot pedaling hand swinging and foot

pressure These approaches are all based on high-performance

two-dimensional rotary TENGs (r-TENG) Enabled by a design of

two radial-arrayed 1047297ne electrodes that are complementary on

the same plane the planar-structured r-TENG produces peri-

odically changing triboelectric potential that induces alternat-

ing currents between electrodes At a rotating rate of

500 r min1 it can deliver a continuous ac output that has a

short-circuit current of 075 mA in amplitude and an open-

circuit voltage of 200 V at a frequency of 750 Hz By integrating

the r-TENG with other mechanical components it can effec-

tively utilize motions from different parts of human body When

installed onto a bicycle the r-TENG can convert mechanical

energy of foot pedaling into electricity powering an array of

small electronics as well as charging a cellphone Besides it can

harness energy from arm swinging as well as foot pressing

during normal walking Through a power management circuit

the electric output can be used to charge capacitors and

batteries unambiguously demonstrating the r-TENG as a pro-

mising power source for portable wearable and even poten-

tially implantable electronics

Results and discussions

A r-TENG is composed of mainly two parts a stator and a

rotator as depicted in Figure 1a The rotator is a collection

of 90 radially-arrayed sectors made of copper For the

stator it is composed of mainly three parts a layer of

polymethyl methacrylate (PMMA) as a substrate a layer of

electrodes and a layer of polytetra1047298uoroethylene (PTFE) as

an electri1047297cation layer The electrode layer is composed of

electrode A and electrode B which have complementary

patterns separated by 1047297ne gaps in between as shown in the

zoom-in sketches of the inner and outer sections of the

stator in Figure 1a As photographed in Figure 1b and c both

Figure 1 Structural design and working principle of the r-TENG (a) Schematic sketches of the r-TENG (b c) Photographs of a rotatorand a stator (scale bar 3 cm) (d) Charge distribution on open-circuit condition (e) Charge distribution on short-circuit condition







[1724]












SY Kuang et al12






























direction

















practical use
































Movie S2






















stored















SY Kuang et al14




































Conclusions

















Acknowledgment




presented here




References



(2006) 175



[6] AD Kuo Science 309 (2005) 1686



(2015) 126











(2014) 33


(2014) 3426


Adv Mater 26 (2014) 3788




(2014) 8011







722
















candidate







micro-nano-systems









ef 1047297ciency












into electricity














SY Kuang et al16






[1724]












SY Kuang et al12






























direction

















practical use
































Movie S2






















stored















SY Kuang et al14




































Conclusions

















Acknowledgment




presented here




References



(2006) 175



[6] AD Kuo Science 309 (2005) 1686



(2015) 126











(2014) 33


(2014) 3426


Adv Mater 26 (2014) 3788




(2014) 8011







722
















candidate







micro-nano-systems









ef 1047297ciency












into electricity














SY Kuang et al16






























direction

















practical use
































Movie S2






















stored















SY Kuang et al14




































Conclusions

















Acknowledgment




presented here




References



(2006) 175



[6] AD Kuo Science 309 (2005) 1686



(2015) 126











(2014) 33


(2014) 3426


Adv Mater 26 (2014) 3788




(2014) 8011







722
















candidate







micro-nano-systems









ef 1047297ciency












into electricity














SY Kuang et al16






Movie S2






















stored















SY Kuang et al14




































Conclusions

















Acknowledgment




presented here




References



(2006) 175



[6] AD Kuo Science 309 (2005) 1686



(2015) 126











(2014) 33


(2014) 3426


Adv Mater 26 (2014) 3788




(2014) 8011







722
















candidate







micro-nano-systems









ef 1047297ciency












into electricity














SY Kuang et al16




































Conclusions

















Acknowledgment




presented here




References



(2006) 175



[6] AD Kuo Science 309 (2005) 1686



(2015) 126











(2014) 33


(2014) 3426


Adv Mater 26 (2014) 3788




(2014) 8011







722
















candidate







micro-nano-systems









ef 1047297ciency












into electricity














SY Kuang et al16






micro-nano-systems









ef 1047297ciency












into electricity














SY Kuang et al16

Two-dimensional Rotary Triboelectric

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