Recent advances in tough and self-healing nanocomposite hydrogels for shape morphing and soft actuators

The design of polymers that exhibit both good elasticity and self-healing properties is a highly challenging task. In spite of this, the literature reports highly stretchable self-healing polymers, but most of them exhibit slow elastic recovery behavior, i.e., they can only recover to their original length upon relaxation for a long time after stretching. Herein, a self-healing polymer with a fast elastic recovery property is demonstrated. We used 4-[tris(4-formylphenyl)methyl]benzaldehyde (TFPM) as a tetratopic linker to crosslink a poly(dimethylsiloxane) backbone, and obtained a self-healing polymer with high stretchability and fast elastic recovery upon stretching. The strain at break of the as-prepared polymer is observed at about 1400%. The polymer can immediately recover to its original length after being stretched. The damaged sample can be healed at room temperature with a healing efficiency up to 93% within 1 h. Such a polymer can be used for various applications, such as functioning as substrates or matrixes in soft actuators, electronic skins, biochips, and biosensors with prolonged lifetimes.

Download Full-text

Design of a High-Speed Prosthetic Finger Driven by Peano-HASEL Actuators

Frontiers in Robotics and AI ◽

10.3389/frobt.2020.586216 ◽

2020 ◽

Vol 7 ◽

Author(s):

Zachary Yoder ◽

Nicholas Kellaris ◽

Christina Chase-Markopoulou ◽

Devon Ricken ◽

Shane K. Mitchell ◽

...

Keyword(s):

High Speed ◽

Kinematic Model ◽

Electrical Energy ◽

Dc Motor ◽

Self Healing ◽

Force Output ◽

Prosthetic Limbs ◽

Neuromuscular Systems ◽

Soft Actuators ◽

Prosthetic Finger

Current designs of powered prosthetic limbs are limited by the nearly exclusive use of DC motor technology. Soft actuators promise new design freedom to create prosthetic limbs which more closely mimic intact neuromuscular systems and improve the capabilities of prosthetic users. This work evaluates the performance of a hydraulically amplified self-healing electrostatic (HASEL) soft actuator for use in a prosthetic hand. We compare a linearly-contracting HASEL actuator, termed a Peano-HASEL, to an existing actuator (DC motor) when driving a prosthetic finger like those utilized in multi-functional prosthetic hands. A kinematic model of the prosthetic finger is developed and validated, and is used to customize a prosthetic finger that is tuned to complement the force-strain characteristics of the Peano-HASEL actuators. An analytical model is used to inform the design of an improved Peano-HASEL actuator with the goal of increasing the fingertip pinch force of the prosthetic finger. When compared to a weight-matched DC motor actuator, the Peano-HASEL and custom finger is 10.6 times faster, has 11.1 times higher bandwidth, and consumes 8.7 times less electrical energy to grasp. It reaches 91% of the maximum range of motion of the original finger. However, the DC motor actuator produces 10 times the fingertip force at a relevant grip position. In this body of work, we present ways to further increase the force output of the Peano-HASEL driven prosthetic finger system, and discuss the significance of the unique properties of Peano-HASELs when applied to the field of upper-limb prosthetic design. This approach toward clinically-relevant actuator performance paired with a substantially different form-factor compared to DC motors presents new opportunities to advance the field of prosthetic limb design.

Download Full-text

Dynamic Mussel-Inspired Chitin Nanocomposite Hydrogels for Wearable Strain Sensors

Polymers ◽

10.3390/polym12061416 ◽

2020 ◽

Vol 12 (6) ◽

pp. 1416 ◽

Cited By ~ 3

Author(s):

Pejman Heidarian ◽

Abbas Z. Kouzani ◽

Akif Kaynak ◽

Ali Zolfagharian ◽

Hossein Yousefi

Keyword(s):

Mechanical Properties ◽

Polyacrylic Acid ◽

Strain Sensors ◽

Self Healing ◽

Network Stability ◽

Ferric Ions ◽

Trade Off ◽

Nanocomposite Hydrogels ◽

Healing Efficiency ◽

Hydrogel Network

It is an ongoing challenge to fabricate an electroconductive and tough hydrogel with autonomous self-healing and self-recovery (SELF) for wearable strain sensors. Current electroconductive hydrogels often show a trade-off between static crosslinks for mechanical strength and dynamic crosslinks for SELF properties. In this work, a facile procedure was developed to synthesize a dynamic electroconductive hydrogel with excellent SELF and mechanical properties from starch/polyacrylic acid (St/PAA) by simply loading ferric ions (Fe3+) and tannic acid-coated chitin nanofibers (TA-ChNFs) into the hydrogel network. Based on our findings, the highest toughness was observed for the 1 wt.% TA-ChNF-reinforced hydrogel (1.43 MJ/m3), which is 10.5-fold higher than the unreinforced counterpart. Moreover, the 1 wt.% TA-ChNF-reinforced hydrogel showed the highest resistance against crack propagation and a 96.5% healing efficiency after 40 min. Therefore, it was chosen as the optimized hydrogel to pursue the remaining experiments. Due to its unique SELF performance, network stability, superior mechanical, and self-adhesiveness properties, this hydrogel demonstrates potential for applications in self-wearable strain sensors.

Download Full-text

Recent Advances in Mussel-Inspired Synthetic Polymers as Marine Antifouling Coatings

Coatings ◽

10.3390/coatings10070653 ◽

2020 ◽

Vol 10 (7) ◽

pp. 653 ◽

Cited By ~ 2

Author(s):

Ioannis Manolakis ◽

Usaid Azhar

Keyword(s):

Amino Acid Derivative ◽

Self Healing ◽

Underwater Adhesion ◽

Marine Biofouling ◽

Recent Advances ◽

Antifouling Coatings ◽

The Common ◽

Active Research ◽

Research Domain ◽

Marine Antifouling

Synthetic oligomers and polymers inspired by the multifunctional tethering system (byssus) of the common mussel (genus Mytilus) have emerged since the 1980s as a very active research domain within the wider bioinspired and biomimetic materials arena. The unique combination of strong underwater adhesion, robust mechanical properties and self-healing capacity has been linked to a large extent to the presence of the unusual α-amino acid derivative l-DOPA (l-3,4-dihydroxyphenylalanine) as a building block of the mussel byssus proteins. This paper provides a short overview of marine biofouling, discussing the different marine biofouling species and natural defenses against these, as well as biomimicry as a concept investigated in the marine antifouling context. A detailed discussion of the literature on the Mytilus mussel family follows, covering elements of their biology, biochemistry and the specific measures adopted by these mussels to utilise their l-DOPA-rich protein sequences (and specifically the ortho-bisphenol (catechol) moiety) in their benefit. A comprehensive account is then given of the key catechol chemistries (covalent and non-covalent/intermolecular) relevant to adhesion, cohesion and self-healing, as well as of some of the most characteristic mussel protein synthetic mimics reported over the past 30 years and the related polymer functionalisation strategies with l-DOPA/catechol. Lastly, we review some of the most recent advances in such mussel-inspired synthetic oligomers and polymers, claimed as specifically aimed or intended for use in marine antifouling coatings and/or tested against marine biofouling species.

Download Full-text

Visible and infrared three-wavelength modulated multi-directional actuators

Nature Communications ◽

10.1038/s41467-019-12583-x ◽

2019 ◽

Vol 10 (1) ◽

Cited By ~ 31

Author(s):

Bo Zuo ◽

Meng Wang ◽

Bao-Ping Lin ◽

Hong Yang

Keyword(s):

Near Infrared ◽

Light Stimulus ◽

Stimuli Responsive ◽

Liquid Crystal Elastomer ◽

Shape Morphing ◽

Actuation System ◽

Directional Movement ◽

Actuator System ◽

Soft Actuators ◽

Scientific Attention

Abstract In recent years, light-guided robotic soft actuators have attracted intense scientific attention and rapidly developed, although it still remains challenging to precisely and reversibly modulate the moving directions and shape morphing modes of soft actuators with ease of stimulating operation. Here we report a strategy of building a multi-stimuli-responsive liquid crystal elastomer soft actuator system capable of performing not only multi-directional movement, but also different shape morphing modes. This strategy is based on the selective stimulation of specific domains of the hierarchical structured actuator through the modulation of three wavelength bands (520, 808, 980 nm) of light stimulus, which release the actuation system from light scanning position/direction restriction. Three near-infrared dual-wavelength modulated actuators and one visible/infrared tri-wavelength modulated multi-directional walker robot are demonstrated in this work. These devices have broad application prospects in robotic and biomimetic technology.

Download Full-text

Recent advances in shear‐thinning and self‐healing hydrogels for biomedical applications

Journal of Applied Polymer Science ◽

10.1002/app.48668 ◽

2020 ◽

Vol 137 (25) ◽

pp. 48668 ◽

Cited By ~ 18

Author(s):

Selen Uman ◽

Abhishek Dhand ◽

Jason A. Burdick

Keyword(s):

Biomedical Applications ◽

Shear Thinning ◽

Self Healing ◽

Recent Advances

Download Full-text

Recent advances in plasticized PVC gels for soft actuators and devices: a review

Journal of Materials Chemistry C ◽

10.1039/c9tc04366g ◽

2019 ◽

Vol 7 (42) ◽

pp. 12991-13009 ◽

Cited By ~ 7

Author(s):

Yi Li ◽

Mingfei Guo ◽

Yanbiao Li

Keyword(s):

Vinyl Chloride ◽

Electric Stimulation ◽

Electroactive Polymers ◽

Plasticized Pvc ◽

Poly Vinyl Chloride ◽

Recent Advances ◽

Soft Actuators

Plasticized poly(vinyl chloride) (PVC) gels belong to a class of electroactive polymers (EAPs), which have the ability to realize bending motion, contractile motion, extended motion and crawling motion under electric stimulation.

Download Full-text