A1 Refereed original research article in a scientific journal
Biomimetic Microfractals Based Flexible Triboelectric Nanogenerators; 
Authors: Barua, Amit; Matić, Mislav; Pitner, Ana‐Marija; Gogoi, Rituporn; Kumar, Aman; Poljak, Mirko; Koivikko, Anastasia; Sharma, Vipul
Publisher: Wiley
Publication year: 2026
Journal: Advanced Functional Materials
Article number: e77314
ISSN: 1616-301X
eISSN: 1616-3028
DOI: https://doi.org/10.1002/adfm.77314
Publication's open availability at the time of reporting: Open Access
Publication channel's open availability : Partially Open Access publication channel
Web address : https://doi.org/10.1002/adfm.77314
Self-archived copy’s web address: https://research.utu.fi/converis/portal/detail/Publication/526850750
Self-archived copy's licence: CC BY
Self-archived copy's version: Publisher`s PDF
Flexible TENGs are promising for self-powered wearables, but combining high output, mechanical compliance, and low material use remains challenging. Here, we report a biomimetic microfractal TENG (BM-TENG) inspired by leaf-skeleton vascular architectures, where the hierarchical network serves as both porous current-collector scaffold and template for triboelectric surface replication. Copper nanowires immobilized along the microfractal pathways form guided and locally bundled conductive networks, enabling a low sheet resistance of ∼15 Ω sq−1 and >1000 fold reduction in sheet resistance compared with a planar control. Replication of the same architecture into electrospun Nylon-6 and PVDF layers creates a compliant multiscale topography that enhances charge generation. The BM-TENG delivers ∼52 V open-circuit voltage, ∼3.2 µA short-circuit current, and ∼67.24 nC transferred charge per cycle while using 50% lower CuNW loading, compared with ∼26 V, ∼1.23 µA, and ∼27.35 nC for the planar control. Using projected device area as the primary normalization basis, BM-TENG achieves a current density of ∼3 mA m−2 and power density of ∼136.91 mW m−2, compared with ∼1.13 mA m−2 and 135.80 mW m−2 for the planar control. As secondary metrics, effective-material-area normalization gives ∼10 mA m−2 and ∼456.35 mW m−2 for the BM-TENG. The device also maintains stable output over ∼10000 cycles.
Keywords:
current density, nanogenerator, nanowire, planar, power density, sheet resistance, triboelectric effect, VOLTAGE
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Funding information in the publication:
This work was supported by the Research Council of Finland through the DURATRANS project (Grant Number 364408, 2024–2027) under the M-ERA.Net framework. The authors are thankful to the Materials Research Infrastructure (MARI) and Sustainable Fabrication (SusFab) at the University of Turku for infrastructure facilities. The authors acknowledge Azadeh Keshavarz for their assistance with dip coating experiments and Akseli Nykänen from the Department of Mechanical and Materials Engineering, University of Turku, for their assistance with the linear motor setup. Amit Barua is thankful to the Finnish Cultural Foundation and Turku University Foundation for providing financial support. During the preparation of this work, the authors used ChatGPT (OpenAI) to improve the readability and language of the manuscript and ChatGPT image generation (OpenAI) to assist in creating the conceptual illustration of the leaf skeleton in Figure 1a,b. The illustration is schematic only and does not represent experimental data. Following the use of these tools, the authors carefully reviewed and edited all content, verified the scientific accuracy of the figure and manuscript, and take full responsibility for the content of this publication.
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