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Chemically programmable microrobots weaving a web from hormones

Nature Machine Intelligence volume 2, pages 711–718 (2020)Cite this article

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Abstract

The occurrence of synthetic and natural hormones in an aqueous environment poses significant risks to humans because of their endocrine-disrupting activity. Autonomous self-propelled and remotely actuated nano/microrobots have emerged as a new field that encompasses a wide range of potential applications, including sensing, detection and elimination/degradation of emerging pollutants. In this work, we develop programmable polypyrrole-based (PPy, outer functional layer) microrobots incorporated with a Pt catalytic layer and paramagnetic iron nanoparticles (Fe3O4) to provide self-propulsion and a magnetic response for the highly efficient removal of oestrogenic pollutants. As the pH of the tested water alters, the surface charge of PPy/Fe3O4/Pt microrobots gradually changes, leading to affinity modulation. As microrobots move inside the solution, they collect oestrogen fibres and subsequently weave macroscopic webs on the surface. Our results suggest that motion-controllable microrobots with adjustable surface chemistry could provide a suitable platform for the highly efficient removal of hormonal pollutants.

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Fig. 1: Schematic of microrobots function.
Fig. 2: Magnetic field effect on PPy/Fe3O4/Pt microrobots.
Fig. 3: Programmable strategy for the PPy/Fe3O4/Pt microrobots.
Fig. 4: Removal/photodegradation of α-oestradiol using PPy/Fe3O4/Pt microrobots.
Fig. 5: XPS study of microrobots before and after oestrogen removal experiments.

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Data availability

Data for the figures presented in this paper are provided in the Supplementary Information and in the FigShare repository (https://doi.org/10.6084/m9.figshare.12979910.v1). Source data are provided with this paper.

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Acknowledgements

M.P. was supported by the Ministry of Education, Youth and Sports (Czech Republic) grant no. LL2002 under the ERC CZ programme. B.K. was supported by the Czech Science Foundation (GACR no. 20-20201S).

Author information

Authors and Affiliations

  1. Center for Advanced Functional Nanorobots, Department of Inorganic Chemistry, Faculty of Chemical Technology, University of Chemistry and Technology Prague, Prague, Czech Republic

    Lukas Dekanovsky, Bahareh Khezri, Filip Novotny, Jan Plutnar & Martin Pumera

  2. Central Laboratories, University of Chemistry and Technology Prague, Prague, Czech Republic

    Zdeňka Rottnerova

  3. Department of Chemical and Biomolecular Engineering, Yonsei University, Seoul, South Korea

    Martin Pumera

  4. Future Energy and Innovation Laboratory, Central European Institute of Technology, Brno University of Technology, Brno, Czech Republic

    Martin Pumera

Authors
  1. Lukas Dekanovsky
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Contributions

L.D. and M.P. conceived the idea. L.D. performed the synthesis and characterization of the microrobots. B.K. measured the UV–vis characteristics for α-oestrogen compound decontamination by the microrobots. F.N. performed numerical simulations. J.P. performed XPS characterization of the microrobots. Z.R. performed characterization of the liquid samples by analytical methods. M.P. and B.K. supervised the research. All authors contributed to writing the manuscript.

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Correspondence to Bahareh Khezri or Martin Pumera.

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Extended data

Extended Data Fig. 1 SEM images and EDS mapping of microrobots.

a, EDS after electropolymerization of PPy (PPy base tube); b, EDS after Pt electrodeposition (PPy/Pt tube) and also; c, Final PPy/Fe3O4/Pt microrobots; d, SEM and corresponding EDS mapping for Fe and Pt with EDS spectra of the observed area; e, STEM image of catalytic Pt layer inside the tube.

Extended Data Fig. 2 SEM images of tubular surface morphologies.

a, Pristine PPy tube (without Pt electrodeposition and also Fe3O4 NPs incorporation); b, PPy/Pt tube, and c, PPy/Fe3O4/Pt microrobots.

Extended Data Fig. 3 PPy/Fe3O4/Pt microrobots’ motion characterization.

a, Their speed in relation to H2O2 concentration and b, Corresponding microscopic images of the microrobots’ motion in different H2O2 concentration.

Source data

Extended Data Fig. 4 Selectivity study of removal efficiency of PPy-based microrobots.

a, Section i-ii represents removal efficiency for Pyrranine dye with microrobots (ii) and without (i); section iii-iv represents experiments carried out with Rhodamine B with microrobots (iv) and without (iii); section v-vi represents removal efficiency for Methylene Blue with microrobots (v) and without (vi); section vii-viii serves for comparison of removal efficiency for 17α-ethynylestradiol with microrobots (viii) and without (vii); b, absorption spectra of organic dyes and c, their chemical structures.

Source data

Extended Data Fig. 5 Numerical simulation of the pressure and fluid velocity.

a, Numerical simulation of a 12.4 × 4.4 µm microrobot speeding at 140 µm s−1 through water.; b, Similar simulated situation but with the addition of mass to the microrobot body (Colormap represents pressure field; red arrows represent fluid flow with the microrobot as a frame of reference).

Source data

Supplementary information

Supplementary Information

Supplementary Figs. 1–6, Table1 and notes 1–5.

Supplementary Video 1

The synergic effect of bubble and magnetic propulsion in navigating of microrobots.

Supplementary Video 2

The directional microrobot reorientation in the presence of a rotating magnetic field.

Supplementary Video 3

The transformation of the fibrous texture to one compact piece which can be easily removed by a static external magnetic field.

Source data

Source Data Fig. 3

Data for presented ζ-potential measurements.

Source Data Fig. 4

Removal efficiency for hormones.

Source Data Fig. 5

XPS source data.

Source Data Extended Data Fig. 3

Statistic source data from speed tracking of microrobots propelled by hydrogen peroxide.

Source Data Extended Data Fig. 4

Selectivity data source.

Source Data Extended Data Fig. 5

Source data for numerical simulation.

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Dekanovsky, L., Khezri, B., Rottnerova, Z. et al. Chemically programmable microrobots weaving a web from hormones. Nat Mach Intell 2, 711–718 (2020). https://doi.org/10.1038/s42256-020-00248-0

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