Currently soft robots primarily rely on pneumatics and geometrical asymmetry to achieve locomotion, which limits their working range, versatility, and other untethered functionalities. In this paper, we introduce a novel approach to achieve locomotion for soft robots through dynamically tunable friction to address these challenges, which is achieved by subsurface stiffness modulation (SSM) of a stimuli-responsive component within composite structures. To demonstrate this, we design and fabricate an elastomeric pad made of polydimethylsiloxane (PDMS), which is embedded with a spiral channel filled with a low melting point alloy (LMPA). Once the LMPA strip is melted upon Joule heating, the compliance of the composite structure increases and the friction between the composite surface and the opposing surface increases. A series of experiments and finite element analysis (FEA) have been performed to characterize the frictional behavior of these composite pads and elucidate the underlying physics dominating the tunable friction. We also demonstrate that when these composite structures are properly integrated into soft crawling robots inspired by inchworms and earthworms, the differences in friction of the two ends of these robots through SSM can potentially be used to generate translational locomotion for untethered crawling robots.
Recently, a novel concept to realize dynamically tunable dry adhesion via subsurface stiffness modulation (SSM) in a composite core–shell structure has been introduced and demonstrated for gripping and release of objects. Here, a variant form of the composite core–shell design is proposed to significantly improve the performance of dynamically tunable dry adhesion in terms of activation time and activation voltage. Specifically, composite pillars with an embedded microfluidic channel filled with a low melting point alloy (LMPA) are fabricated, and the adhesion of the pillars is characterized as a function of LMPA state: either melted or solid. The effects of the thickness and in‐plane pattern of the LMPA channel, as well as the depth at which it is embedded on tunable adhesion are investigated. Experiments show that the effective adhesion strength can be reduced up to 50%, equivalent to a 2× change in dry adhesion when the LMPA is melted. Finite element analysis of the stress distribution change under SSM shows that the experimentally observed tunable adhesion is primarily due to stiffness change close to the interface. In addition, two technology demonstrations of composite pillars picking and releasing objects with fast activation (≈1 s) and low activation voltages (≈1 V) are included.
more » « less- NSF-PAR ID:
- 10363601
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Advanced Materials Interfaces
- Volume:
- 9
- Issue:
- 7
- ISSN:
- 2196-7350
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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