102
I. Fiorello et al.
4 Conclusions and Future Perspectives
In this work, we analyzed the variation of mechanical properties on G. aparine stems
from the basal to the apical regions using tensile testing. Our preliminary results highlighted significant mechanical differences between the basal and upper stem regions.
As expected, the basal part showed strong stiffness (similarly to climbers [4]) and high
extensibility (similarly to aquatic species [7, 8]), in contrast to the upper parts which had
lower but constant values of stiffness and breaking strains. These findings, in addition
to the presence of directional leaf micro-hooks, may have an evolutionary significance,
preventing the stem breakage due to tugs (i.e., from animals or wind) [6, 7]. Future development of this study will include ad hoc experimental setup to understand the mechanism
at the basis of these high breaking strains and a whole analysis of the stem architecture,
in order to deeper understand the structure-function relationship in stem materials. Furthermore, G. aparine micro-hooks represent an interesting source of inspiration for the
development of artificial systems for reversible attachment on rough surfaces [11–13],
useful also for facilitating robots climbing over a wide range of supports and surfaces
[13].
We believe these deeper morphological characterizations, in addition to our preliminary biomechanical study, will provide the specifications to prototype novel highperforming materials for vine-like soft robots able to operate in unstructured conditions
[3].
Acknowledgments. This work was funded by the European Union’s Horizon 2020 Research and
Innovation Programme under Grant Agreement No 824074 (GrowBot Project).
References
1. Laschi, C., Mazzolai, B., Cianchetti, M.: Soft robotics: technologies and systems pushing the
boundaries of robot abilities. Sci. Robot. 1, eaah3690 (2016)
2. Schmitt, O.H.: Some interesting and useful biomimetic transforms. In: Third Int. Biophysics
Congress, p. 197 (1969)
3. Fiorello, I., Del Dottore, E., Tramacere, F., Mazzolai, B.: Taking inspiration from climbing
plants: methodologies and benchmarks–A review. Bioinspiration Biomimetics 15(3), 031001
(2020)
4. Rowe, N.P., Speck, T.: Stem biomechanics, strength of attachment, and developmental
plasticity of vines and lianas. Ecology of Lianas, pp. 323–341 (2014)
5. Speck, T., Burgert, I.: Plant stems: functional design and mechanics. Annu. Rev. Mater. Res.
41, 169–193 (2011)
6. Bauer, G., Klein, M.C., Gorb, S.N., Speck, T., Voigt, D., Gallenmüller, F.: Always on the
bright side: the climbing mechanism of Galium aparine. Proc Biol. Sci. 278, 2233–2239
(2011)
7. Goodman, A.M.: Mechanical adaptations of cleavers (Galium aparine). Ann. Bot. 95, 475–480
(2004)
8. Usherwood, J., Ennos, A., Ball, D.: Mechanical and anatomical adaptations in terrestrial and
aquatic buttercups to their respective environments. J. Exp. Bot. 48, 1469–1475 (1997)
9. Niklas, K.J., Spatz, H.-C.: Plant physics. University of Chicago Press (2012)
I. Fiorello et al.
4 Conclusions and Future Perspectives
In this work, we analyzed the variation of mechanical properties on G. aparine stems
from the basal to the apical regions using tensile testing. Our preliminary results highlighted significant mechanical differences between the basal and upper stem regions.
As expected, the basal part showed strong stiffness (similarly to climbers [4]) and high
extensibility (similarly to aquatic species [7, 8]), in contrast to the upper parts which had
lower but constant values of stiffness and breaking strains. These findings, in addition
to the presence of directional leaf micro-hooks, may have an evolutionary significance,
preventing the stem breakage due to tugs (i.e., from animals or wind) [6, 7]. Future development of this study will include ad hoc experimental setup to understand the mechanism
at the basis of these high breaking strains and a whole analysis of the stem architecture,
in order to deeper understand the structure-function relationship in stem materials. Furthermore, G. aparine micro-hooks represent an interesting source of inspiration for the
development of artificial systems for reversible attachment on rough surfaces [11–13],
useful also for facilitating robots climbing over a wide range of supports and surfaces
[13].
We believe these deeper morphological characterizations, in addition to our preliminary biomechanical study, will provide the specifications to prototype novel highperforming materials for vine-like soft robots able to operate in unstructured conditions
[3].
Acknowledgments. This work was funded by the European Union’s Horizon 2020 Research and
Innovation Programme under Grant Agreement No 824074 (GrowBot Project).
References
1. Laschi, C., Mazzolai, B., Cianchetti, M.: Soft robotics: technologies and systems pushing the
boundaries of robot abilities. Sci. Robot. 1, eaah3690 (2016)
2. Schmitt, O.H.: Some interesting and useful biomimetic transforms. In: Third Int. Biophysics
Congress, p. 197 (1969)
3. Fiorello, I., Del Dottore, E., Tramacere, F., Mazzolai, B.: Taking inspiration from climbing
plants: methodologies and benchmarks–A review. Bioinspiration Biomimetics 15(3), 031001
(2020)
4. Rowe, N.P., Speck, T.: Stem biomechanics, strength of attachment, and developmental
plasticity of vines and lianas. Ecology of Lianas, pp. 323–341 (2014)
5. Speck, T., Burgert, I.: Plant stems: functional design and mechanics. Annu. Rev. Mater. Res.
41, 169–193 (2011)
6. Bauer, G., Klein, M.C., Gorb, S.N., Speck, T., Voigt, D., Gallenmüller, F.: Always on the
bright side: the climbing mechanism of Galium aparine. Proc Biol. Sci. 278, 2233–2239
(2011)
7. Goodman, A.M.: Mechanical adaptations of cleavers (Galium aparine). Ann. Bot. 95, 475–480
(2004)
8. Usherwood, J., Ennos, A., Ball, D.: Mechanical and anatomical adaptations in terrestrial and
aquatic buttercups to their respective environments. J. Exp. Bot. 48, 1469–1475 (1997)
9. Niklas, K.J., Spatz, H.-C.: Plant physics. University of Chicago Press (2012)