Biomechanical Characterization
of Hook-Climber Stems for Soft Robotic
Applications
Isabella Fiorello 1,2(B) , Alessio Mondini 1,2 , and Barbara Mazzolai 1(B)
1 Center for Micro-BioRobotics@SSSA, Istituto Italiano di Tecnologia, Pontedera, Italy
{isabella.fiorello,barbara.mazzolai}@iit.it
2 The BioRobotics Institute, Scuola Superiore Sant’Anna, Pontedera, Italy
Abstract. Plants are getting increasing interest from scientists for the development of novel biomimetic products. Especially, the stems of climbing plants possess impressively high-adaptable materials, which can be relevant in robotics for
the development of new machines able to work in unpredictable environments.
In this work, we present a study on the mechanical properties of the stem of the
hook-climber Galium aparine. Three different stem regions (basal, middle and
apical parts) were analyzed in order to investigate how the mechanical properties
vary along the stem. Tensile tests were performed on the different stem parts.
Results demonstrated a significant decrease of Young’s modulus, the breaking
strain and the tensile strength values from the basal to the upper parts. In contrast,
we observed a decrease only in the tensile strength between the middle and apical
parts. The collected data on the mechanical response of natural plant stems will
be used as benchmarks for the design of novel soft robots that can act and move
in real unstructured scenarios for exploration and monitoring tasks.
Keywords: Stem materials · Mechanical properties · Tensile tests · Climbing
plant-inspired soft robots
1 Introduction
The development of novel systems with compliant smart materials able to adapt to
unpredictable environments is fundamental for robotic and engineering applications
[1]. Mimicking the biological features of natural materials can offer new solutions to
address these issues [2]. Among living organisms, climbing plants show interesting
features, especially regarding attachment (i.e., hooks, spines, roots, adhesive pads etc.)
and material properties (i.e., high adaptability, flexibility and resistance to mechanical
stresses), which are fundamental for the development of new self-adaptable growing
machines [3–5]. To this aim, we select the hook-climber Galium aparine L., which is a
semi-self-supporting fast-growing herbaceous plant able to attach to several host plant
species mainly using its leaves, endowed with a ratchet-like climbing mechanism based
on micro-hooks for mechanical interlocking [6]. Indeed, G. aparine has peculiar stem
mechanical properties and impressively high extensibility up to ≈29% before failure
© Springer Nature Switzerland AG 2020
V. Vouloutsi et al. (Eds.): Living Machines 2020, LNAI 12413, pp. 97–103, 2020.
https://doi.org/10.1007/978-3-030-64313-3_11
of Hook-Climber Stems for Soft Robotic
Applications
Isabella Fiorello 1,2(B) , Alessio Mondini 1,2 , and Barbara Mazzolai 1(B)
1 Center for Micro-BioRobotics@SSSA, Istituto Italiano di Tecnologia, Pontedera, Italy
{isabella.fiorello,barbara.mazzolai}@iit.it
2 The BioRobotics Institute, Scuola Superiore Sant’Anna, Pontedera, Italy
Abstract. Plants are getting increasing interest from scientists for the development of novel biomimetic products. Especially, the stems of climbing plants possess impressively high-adaptable materials, which can be relevant in robotics for
the development of new machines able to work in unpredictable environments.
In this work, we present a study on the mechanical properties of the stem of the
hook-climber Galium aparine. Three different stem regions (basal, middle and
apical parts) were analyzed in order to investigate how the mechanical properties
vary along the stem. Tensile tests were performed on the different stem parts.
Results demonstrated a significant decrease of Young’s modulus, the breaking
strain and the tensile strength values from the basal to the upper parts. In contrast,
we observed a decrease only in the tensile strength between the middle and apical
parts. The collected data on the mechanical response of natural plant stems will
be used as benchmarks for the design of novel soft robots that can act and move
in real unstructured scenarios for exploration and monitoring tasks.
Keywords: Stem materials · Mechanical properties · Tensile tests · Climbing
plant-inspired soft robots
1 Introduction
The development of novel systems with compliant smart materials able to adapt to
unpredictable environments is fundamental for robotic and engineering applications
[1]. Mimicking the biological features of natural materials can offer new solutions to
address these issues [2]. Among living organisms, climbing plants show interesting
features, especially regarding attachment (i.e., hooks, spines, roots, adhesive pads etc.)
and material properties (i.e., high adaptability, flexibility and resistance to mechanical
stresses), which are fundamental for the development of new self-adaptable growing
machines [3–5]. To this aim, we select the hook-climber Galium aparine L., which is a
semi-self-supporting fast-growing herbaceous plant able to attach to several host plant
species mainly using its leaves, endowed with a ratchet-like climbing mechanism based
on micro-hooks for mechanical interlocking [6]. Indeed, G. aparine has peculiar stem
mechanical properties and impressively high extensibility up to ≈29% before failure
© Springer Nature Switzerland AG 2020
V. Vouloutsi et al. (Eds.): Living Machines 2020, LNAI 12413, pp. 97–103, 2020.
https://doi.org/10.1007/978-3-030-64313-3_11