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Mechanical energy harvesters with tensile efficiency of 17.4% and torsional efficiency of 22.4% based on homochirally plied carbon nanotube yarns


Improved methods are needed for harvesting mechanical energy. Coiled carbon nanotube yarns, termed twistrons, use stretch-induced changes in electrochemical capacitance to convert mechanical energy to electricity. Elongation of the yarn produces such large lateral Poisson’s ratios that the yarns are highly stretch densified, which contributes to harvesting. Here we report plied twistrons, instead of coiled, which increase the energy conversion efficiency of the yarns from 7.6% to 17.4% for stretch and to 22.4% for twist. This is attributed to additional harvesting mechanisms by yarn stretch and lateral deformations. For harvesting between 2 and 120 Hz, our plied twistron has higher gravimetric peak power and average power than has been reported for non-twistron, material-based mechanical energy harvesters. We sew the twistrons into textiles for sensing and harvesting human motion, deploy them in salt water for harvesting ocean wave energy and use them to charge supercapacitors.

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Fig. 1: Fabrication, SEM images and sinusoidal tensile deformation characterization of homochiral three-ply twisted yarn harvesters in 0.1 M aqueous HCl electrolyte.
Fig. 2: Characterization of the tensile and torsional energy conversion efficiencies of three-ply yarn twistrons.
Fig. 3: Dependencies of OCV on strain, yarn density, lateral pressure and the ratio of capacitance change to the capacitance for a given deformation.
Fig. 4: Applications and comparisons of performance with literature results.

Data availability

All of the data generated in this study are included in the published Article and its Supplementary Information.


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Support in the United States was from Navy grants ONR/STTR N68335-18-C-0368 (R.H.B.) and ONR N00014-22-1-2569 (R.H.B.), Air Force Office of Scientific Research grants N68335-19C-0303 (R.H.B.) and FA9550-21-1-0455 (R.H.B.), Robert A. Welch Foundation grant AT-0029 (R.H.B.), National Science Foundation grant CMMI-1636306 (H.L.) and Department of Energy grant DE-NA0003962 (H.L.).

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Authors and Affiliations



M.Z. and R.H.B. conceived of and initiated the project. C.H. synthesized the CNT forests. M.Z., W.C., Z.W., S.F., A.E.A., A.A.Z., J.O., J.H.M., J.W.P. and S.J.K. fabricated the CNT yarns and measured their performance. M.Z., W.C., S.F. and C.H. characterized the microstructure of the CNT yarns. M.Z., W.C., S.F., R.Z., H.L., E.G. and R.H.B. conducted the X-ray tomography characterization. M.Z., W.C., Z.W., S.F., A.E.A. and R.H.B. demonstrated the applications of CNT yarns. All authors conducted the data analysis and prepared the manuscript.

Corresponding author

Correspondence to Ray H. Baughman.

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Competing interests

Z.W., R.H.B., M.Z., W.C., S.F., S.J.K. and J.H.M. are among the inventors of provisional US patent application number 63/235,023, submitted jointly by the Board of Regents, University of Texas System (for the University of Texas at Dallas) and Industry-University Cooperation Foundation of Hanyang University, which covers the design, fabrication, performance and applications of twistron mechanical energy harvesters. The remaining authors declare no competing interests.

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Nature Energy thanks Soo Jin Adrian Koh and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Supplementary Figs. 1–61, Tables 1 and 2 and references 1–90.

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Zhang, M., Cai, W., Wang, Z. et al. Mechanical energy harvesters with tensile efficiency of 17.4% and torsional efficiency of 22.4% based on homochirally plied carbon nanotube yarns. Nat Energy 8, 203–213 (2023).

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