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Page 2 of 35 Villeda-Hernandez et al. Soft Sci 2024;4:14 https://dx.doi.org/10.20517/ss.2023.52

INTRODUCTION
The evolution of robotics over the past decades has transformed the field and yielded more interactive and
[1-3]
collaborative systems . From agriculture and commodities to science, medicine, and manufacturing
industries, robotic advancements have become embedded as critical components in diverse sectors of
[4,5]
human development . Historical events such as global pandemics and wars have underscored the
significance of contingency robotic systems. Contingency systems capable of operating in hazardous
environments or performing repetitive and collaborative tasks will allow humans to shift their focus to
[6,7]
capital and knowledge-intensive industries .

The field of soft robotics draws inspiration from nature to create systems that replicate the adaptability,
fluidity, and function of biological entities, with performance approaching that of the mimicked natural
systems . Beyond mimicking biological structures, soft robotics also aims to develop biocompatible systems
[8]
to interact synergically with biological structures. As soft robotics and robotics evolve, we witness more
autonomous, adaptable, modular, safer, and controllable systems that positively influence and benefit
[9]
society . It is paramount for industry and researchers to take safety and sustainability into consideration
when designing or conceptualizing new systems . By developing systems that can mimic, interact, and
[10]
preserve biological systems, a complete soft robotics “triad” can be achieved [Figure 1A].
[11]
Developing systems capable of interacting with soft biological tissues (e.g., in nature to collect biological
samples, or interacting with humans, as outlined below) is a major goal in soft robotics. Pneumatic soft
actuators are a popular choice for developing bio-inspired systems by arranging multiple positive and
negative pressure-actuated systems to mimic limbs. Hu et al. introduced positive and negative pressure-
[12]
driven pneumatic actuators arranged in the shape of a glove system for hand rehabilitation [Figure 1B] .
Recently, non-invasive pneumatic and hydraulic systems for sample collection and exploration in shallow
waters have been proposed and tested [13-15] . Sinatra et al. developed a soft robotic system with ultra-gentle
[16]
manipulation for interacting with softer species such as jellyfish [Figure 1C] . Other systems with the
ability for gentle manipulation can also interact with other natural specimens such as fruits and vegetables
using pneumatic grippers. Wang et al. proposed a novel soft robotic gripper comprised of positive pressure-
driven robotic fingers and a negative pressure-driven suction cup for apple harvesting [Figure 1D] .
[17]
However, the realm of soft robotics is not limited to non-human interactions. A key research focus lies in
developing implantable soft robots designed to address and prevent muscular failure-related issues. These
[18]
[19]
medical conditions, including urinary incontinence (UI) , muscular dystrophy (MD) , sarcopenia, and
[20]
other muscle-related complications , arise due to disease, aging, or trauma. There is widespread interest in
preventing and restoring muscular malfunctioning of damaged muscle tissue and other medical conditions
related to the mobility and control of smooth or rough muscles [21-24] . Rehabilitation gloves , apparel that
[25]
improves mobility , and other important topics related to well-being and opportunities to increase life
[26]
quality are of significant interest to soft roboticists [27,28] . By exploring innovative soft robotic solutions,
researchers aim to improve treatment and rehabilitation options for patients suffering from these
debilitating conditions.

While several mechanisms drive soft robots, pneumatic soft actuators are among the most popular and
researched soft actuators; their simple mechanism and compliance make them great candidates for
achieving high mechanical forces (up to ~140 N) and specific control. Their reliance on changes in
[29]
pressures - particularly gases - to induce deformation underpins their popularity . Among the different
[30]
pressure sources commonly used to power soft actuators (see Section “Power sources”), gas evolution
reactions (GERs) and gas consumption reactions (GCRs) have a promising role as innovative power sources