Functional PDMS Elastomers: Bulk Composites, Surface Engineering, and Precision Fabrication

Abstract

Polydimethylsiloxane (PDMS)—the simplest and most common silicone compound—exemplifies the central characteristics of its class and has attracted tremendous research attention. The development of PDMS‐based materials is a vivid reflection of the modern industry. In recent years, PDMS has stood out as the material of choice for various emerging technologies. The rapid improvement in bulk modification strategies and multifunctional surfaces has enabled a whole new generation of PDMS‐based materials and devices, facilitating, and even transforming enormous applications, including flexible electronics, superwetting surfaces, soft actuators, wearable and implantable sensors, biomedicals, and autonomous robotics. This paper reviews the latest advances in the field of PDMS‐based functional materials, with a focus on the added functionality and their use as programmable materials for smart devices. Recent breakthroughs regarding instant crosslinking and additive manufacturing are featured, and exciting opportunities for future research are highlighted. This review provides a quick entrance to this rapidly evolving field and will help guide the rational design of next‐generation soft materials and devices.

Soft Microstructure Arrays: A Multifunctional Microsystem for Mass Transport, Energy Transformation, and Surface Manipulation

“…For example, traditionally, covalently cross-linked polymers face a trade-off between stiffness and extensibility, a challenge that can be tackled through advancements in materials science, compounding methods, and functionalization chemistry to produce superior elastomers. 191 In addition, the design strategy and fabrication method for the microstructure need to be further advanced. While most of the shapes of the SMA unit discussed in this review are pretty simple (e.g., pyramid, hemisphere, column), we should expect more complicated and specifically design structures for certain applications of SMAs in the future.…”

“…The cross-linked PDMS offers several key attributes, such as hydrophobicity (with a water contact angle (WCA) of ∼110°), biocompatibility, rapid moldability, chemical inertness, and nontoxicity. Additionally, its excellent thermal stability until 400 °C, − low electrical conductivity (∼10 –14 S·m –1 ), and high transparency from 240 to 1100 nm wavelengths make PDMS a versatile material for diverse applications . Ecoflex, a two-component silicone with rapid ambient curing, , spans a hardness range from Shore 00-10 to Shore 00-65.…”

“…In general, soft materials for SMAs can be extended and further developed. For example, traditionally, covalently cross-linked polymers face a trade-off between stiffness and extensibility, a challenge that can be tackled through advancements in materials science, compounding methods, and functionalization chemistry to produce superior elastomers . In addition, the design strategy and fabrication method for the microstructure need to be further advanced.…”

Chemical Patterning on Nanocarbons: Functionality Typewriting

“…The intrinsic electrical properties of SWCNTs are governed by their structural attributes, including chirality-a defining characteristic detailing the angular alignment of the graphene lattice-which imbues SWCNTs with metallic or semiconducting behavior. Over the past three decades, surface functionalization of CNTs has undergone extensive investigation, embracing both covalent and non-covalent strategies [28,[37][38][39][40][41][42], enriching the versatility of these materials across an array of applications such as compositing [43], sensing devices, and materials processing. Nevertheless, the ramifications of functionalization on the fundamental electronic and optical properties of CNTs remained obscure until recent breakthroughs.…”

Rugged Island-Bridge Inorganic Electronics Mounted on Locally Strain-Isolated Substrates

“…Second, in the programmable rigidity strategy, cross-linkable polymers and hydrogels are locally regulated through external stimuli such as ultraviolet (UV) exposure or chemical modification. − This approach can provide strong interfacial adhesion between the rigid and stretchable regions owing to the chemically bound homogeneous phases. However, programmable rigidity can lead to loss of stretchability because of the possibility of continuous cross-linking by external stimuli (such as heat or light). , Furthermore, a sufficient strain-isolation effect is difficult in programmed rigidity owing to the limitation in suitably increasing the inherent low-modulus properties of silicon-based polymers. − Therefore, to realize stretchable electronics, it is imperative to go beyond merely employing strain isolation strategies. A substrate design must be conceived that inherently facilitates high strain isolation, while also delivering enhanced mechanical stability at the interface between the rigid and stretchable regions.…”