Plant-Like Tropisms in Artificial Muscles

Light-Driven Multidirectional Bending in Artificial Muscles

Using light to drive polymer actuators can enable spatially selective complex motions, offering a wealth of opportunities for wireless control of soft robotics and active textiles. Here, the integration of photothermal components is reported into shape memory polymer actuators. The fabricated twist-coiled artificial muscles show on-command multidirectional bending, which can be controlled by both the illumination intensity, as well as the chirality, of the prepared artificial muscles. Importantly, the direction in which these artificial muscles bend does not depend on intrinsic material characteristics. Instead, this directionality is achieved by localized untwisting of the actuator, driven by selective irradiation. The reaction times of this bending system are significantly - at least two orders of magnitude - faster than heliotropic biological systems, with a response time up to one second. The programmability of the artificial muscles is further demonstrated for selective, reversible, and sustained actuation when integrated in butterfly-shaped textiles, along with the capacity to autonomously orient toward a light source. This functionality is maintained even on a rotating platform, with angular velocities of 6°/s, independent of the rotation direction. These attributes collectively represent a breakthrough in the field of artificial muscles, intended to adaptive shape-changing soft systems and biomimetic technologies.

Consistent Thermal Conductivities of Spring-Like Structured Polydimethylsiloxane Composites under Large Deformation

Flexible and highly thermally conductive materials with consistent thermal conductivity (λ) during large deformation are urgently required to address the heat accumulation in flexible electronics. In this study, spring-like thermal conduction pathways of silver nanowire (S-AgNW) fabricated by 3D printing are compounded with polydimethylsiloxane (PDMS) to prepare S-AgNW/PDMS composites with excellent and consistent λ during deformation. The S-AgNW/PDMS composites exhibit a λ of 7.63 W m-1 K-1 at an AgNW amount of 20 vol%, which is ≈42 times that of PDMS (0.18 W m-1 K-1) and higher than that of AgNW/PDMS composites with the same amount and random dispersion of AgNW (R-AgNW/PDMS) (5.37 W m-1 K-1). Variations in the λ of 20 vol% S-AgNW/PDMS composites are less than 2% under a deformation of 200% elongation, 50% compression, or 180° bending, which benefits from the large deformation characteristics of S-AgNW. The heat-transfer coefficient (0.29 W cm-2 K-1) of 20 vol% S-AgNW/PDMS composites is ≈1.3 times that of the 20 vol% R-AgNW/PDMS composites, which reduces the temperature of a full-stressed central processing unit by 6.8 °C compared to that using the 20 vol% R-AgNW/PDMS composites as a thermally conductive material in the central processing unit.

Untethered soft actuators for soft standalone robotics

Soft actuators produce the mechanical force needed for the functional movements of soft robots, but they suffer from critical drawbacks since previously reported soft actuators often rely on electrical wires or pneumatic tubes for the power supply, which would limit the potential usage of soft robots in various practical applications. In this article, we review the new types of untethered soft actuators that represent breakthroughs and discuss the future perspective of soft actuators. We discuss the functional materials and innovative strategies that gave rise to untethered soft actuators and deliver our perspective on challenges and opportunities for future-generation soft actuators.

Highly Efficient Fabrication of Biomimetic Nanoscaled Tendrils for High-Performance PM0.3 Air Filters

Particulate matter pollution has become a serious public health issue, especially with the outbreak of new infectious diseases. However, most existing air filtration materials face challenges such as being too bulky, having high resistance, and a trade-off between filtration efficiency and air permeability. Here, a unique electro-blown spinning technique is used to prepare an air filter made of biomimetic nanoscaled tendril nonwovens (Nano-TN). The introduction of an airflow field significantly increases the whipping frequency and the strain mismatch of composite jets, achieving large-scale and highly efficient preparation of Nano-TN. The resultant Nano-TN has an ultrahigh porosity (97%) and a small pore size (2.9 μm). At the same filtration level, its air resistance is 37% lower than that of traditional straight nanofibrous nonwovens and has a higher dust-holding capacity. Moreover, compared with traditional three-dimensional air filters, the Nano-TN filter is thinner, offering tremendous application prospects in various environmental purification and personal protection fields.