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Page 28 of 35 Villeda-Hernandez et al. Soft Sci 2024;4:14 https://dx.doi.org/10.20517/ss.2023.52

Developing more efficient and controllable chemo-driven pneumatic soft actuation systems and materials
could revolutionize soft robotics and have a wide range of practical applications in fields such as biomedical
engineering and advanced manufacturing.

Design and manufacturing
By exploring and integrating various geometries and material densities, the rapidly growing field of soft
pneumatic actuation has unlocked a broad spectrum of achievable motions (i.e., linear, bending, and
twisting) . Nevertheless, it is paramount to start considering integrating power sources within the design
[169]
of chemo-driven pneumatic actuators. Bio-inspiration is already widely accepted and exploited for soft
robotics and has been a primary source of inspiration for motion and material design [35,170] . For example,
chambers for storing chemicals can be found in many biological systems [171,172] . It is envisaged that a
significant step toward achieving the autonomy of chemo-driven pneumatic systems can be made by
assigning a dedicated compartment for storing reactants and gases.

Safety
As mentioned in Section “Towards continuous actuation: coupling GER and GCRs”, the safety of new
systems that generate pressure or vacuums needs to be carefully understood to inform the design of future
systems. Many of the systems suggested can be controlled via feed ratios, and the products and reactants are
selected to be biocompatible in many cases. Although future work will pave the way for introducing
physical barriers (such as flow gates) to prevent uncontrolled chemical reactions, consideration has to be
given to the chemical degradation of the materials used over time, embedded reaction chambers and their
degradation and the ability of the system to vent in a safe fashion when potentially overpressurized.

Sustainability
The concerns regarding sustainability come under two areas. Firstly, it is crucial for future systems to focus
on regenerating starting materials for both GERs and GCRs. Achieving sustainability may involve creating
closed loops by coupling these reactions, although the number of effective cycles will be inherently limited.
An innovative approach is to generate starting materials from biological sources, such as harnessing gas
production from gut bacteria or leveraging natural pH variations within biological systems, to maintain the
viability of these meticulously designed systems. Secondly, when considering the response of the actuator to
these reactions, it is essential to address both the degradation of the systems and the potential loss of
functionality. To ensure compatibility with biological systems, comprehensive testing over repeated cycles is
necessary, particularly focusing on resolving issues related to the reservoirs and power sources of actuators.
To address the concern of gas loss through material fatigue (and degradation) with prolonged use, recent
advances in self-healing materials offer a promising solution. For instance, a study by Terryn et al.
demonstrates the development of self-healing elastomers, thereby mitigating the risk of gas leakage and
[173]
prolonging the functional lifespan of actuators . Incorporating such self-healing systems within the
makeup of actuators could significantly enhance the sustainability and durability of soft pneumatic
actuators, especially in long-term application settings.

In conclusion, we believe that significant opportunities exist, in carefully chosen application areas, to
expand the use of chemo-pneumatic soft actuation. Although this field is in its early stages of development,
noteworthy pathways already exist related to a) the application of bio-inspired design and b) the rules for
safe and long-term sustainable solutions to soft actuation. The hope is that this overview of the field, the
detailed discussion of all aspects of efficiency and control, design, safety, and sustainability, as shown in the
roadmap presented in Figure 10, will lead to innovation in the research, development and application of
chemo-driven pneumatic actuators.