Bioinspired Smart Materials Research Articles

4D Printing of Seed Capsule‐Inspired Hygro‐Responsive Structures via Liquid Crystal Templating‐Assisted Vat Photopolymerization

AbstractThe creatures in nature exhibit dynamic responses to environmental stimuli through their hierarchical architectures. Benefiting from gradient porous structures, Delosperma nakurense opens its protective valves of the seed capsules when hydrated with liquid water, increasing the likelihood that seeds are dispersed under conditions favorable to germination. Here, a versatile 4D printing technology, namely liquid crystal templating‐assisted vat photopolymerization (LCT‐VPP), which can fabricate bioinspired porous structures with hygro‐responsive capabilities by utilizing photopolymerization induced phase separation (PIPS) and liquid crystals (LCs) electro‐alignment is reported. PIPS within the LCs/nanofiller composites leads to the formation of submicrometer gradient porous structures after extracting nonreactive LCs. The electric field enables the programmable alignment of LCs, which in turn elongates the porous structures and aligns nanofillers. In addition, the programmable arranged nanofillers by the templated LCs enhance the degree of deformation and thus the resulting composites exhibit high shape control accuracy, fast dynamic response, and high reliability. This study opens a perspective for designing bioinspired smart materials with the special spatial distribution of porous structures. The results reported here can give rise to various potential applications in soft robots, smart anticounterfeiting devices, flexible sensors, and ultrafiltration membrane.

Bioinspired Synergistic Photochromic Luminescence and Programmable Liquid Crystal Actuators.

Bioinspired smart materials with synergistic allochroic luminescence and complex deformation are expected to play an important role in many areas of science and technology. However, it is still challenging to fabricate such soft actuators with high programmability that can be manipulated in situ with high spatial resolution. Herein, we have incorporated terminally functionalized aggregation-induced emission active tetraphenylethene derivative and photochromic spiropyran moieties into the networks of liquid crystal elastomers through covalent bonding to obtain the synergistic photochromic luminescence and programmable soft actuators. Bio-mimic functions and light-induced auxetic metamaterial-like devices were shown to be feasible based on the combination of assembly and origami-programming strategy. These bioinspired devices with synergistic photochromic luminescence and complex photodeformation abilities provide an elegant strategy to design multi-functional liquid crystal actuators.

Nucleobase morpholino \u03b2 amino acids as molecular chimeras for the preparation of photoluminescent materials from ribonucleosides

Bioinspired smart materials represent a tremendously growing research field and the obtainment of new building blocks is at the molecular basis of this technology progress. In this work, colloidal materials have been prepared in few steps starting from ribonucleosides. Nucleobase morpholino β-amino acids are the chimera key intermediates allowing Phe–Phe dipeptides’ functionalization with adenine and thymine. The obtained compounds self-aggregate showing enhanced photoluminescent features, such as deep blue fluorescence and phosphorescence emissions.

Extended multiscale finite element method based on polyhedral coarse grid elements for heterogeneous materials and structures

In this paper, a three-dimensional multiscale approach based on the theoretical framework of the multiscale finite element method is proposed to solve the behaviors of heterogeneous materials and structures containing irregular polyhedral inclusions with arbitrary numbers of vertices and faces. The heterogeneous structures are meshed with arbitrary polyhedral elements with coarse-scale sizes, according to the geometric information of irregular inclusions. The mechanical information about the polyhedral inclusions at the fine-scale are constructed through multiscale base functions for the macroscopic deformations of the structures. In these constructions, an extended linear boundary condition is proposed to construct the multiscale base functions for the irregular polyhedral inclusions. The equivalent stiffness matrix of the polyhedral coarse-grid elements can be derived with the multiscale base functions, and the mechanical response of the structures can be calculated at the macroscale. This work further concentrates on the applications of the proposed method to simulate the smart materials and structures that composed of polyhedral heterogeneous inclusions, such as bio-inspired smart materials with inspirations from nastic movements of plants. The multiscale base functions for both fluid and solid phases of the actuators are constructed for such smart materials with multiphysics characteristics. Numerical examples about reinforced concrete structures, heterogeneous cantilever beam and smart wing structures are analyzed by the proposed multiscale method, and the results are compared with those calculated by the standard finite element method. A good correlation between the two methods is observed, providing the evidence that the proposed method can accurately predict the behaviors of the heterogeneous materials with polyhedral inclusions.

Bioinspired Smart Materials for Directional Liquid Transport

Bioinspired materials capable of driving liquid in a directional manner have wide potential applications in many chemical engineering processes, such as heat transfer, separation, microfluidics, and so on. Numerous natural materials and systems such as spider silk, cactus, shorebirds, desert beetles, butterfly wing, and Nepenthes alata have been serving as a rich source of inspirations in the area. During the last decades, great efforts have been devoted to design bioinspired smart materials for directional liquid transport. In this review, we begin by introducing several natural materials and systems with surface structural features contributing for their directional liquid transport property, followed by the basic concepts and theories about surface wettability, droplet motion, and driving forces with different structural features. Then, we summarize some typical applications of such bioinspired smart materials in industrial processes and chemical engineering, particularly in heat transfer, separation, ...

Learning from nature: binary cooperative complementary nanomaterials.

In this Review, nature-inspired binary cooperative complementary nanomaterials (BCCNMs), consisting of two components with entirely opposite physiochemical properties at the nanoscale, are presented as a novel concept for the building of promising materials. Once the distance between the two nanoscopic components is comparable to the characteristic length of some physical interactions, the cooperation between these complementary building blocks becomes dominant and endows the macroscopic materials with novel and superior properties. The first implementation of the BCCNMs is the design of bio-inspired smart materials with superwettability and their reversible switching between different wetting states in response to various kinds of external stimuli. Coincidentally, recent studies on other types of functional nanomaterials contribute more examples to support the idea of BCCNMs, which suggests a potential yet comprehensive range of future applications in both materials science and engineering.

Smart body armor inspired by flow in bone

An understanding of biomaterials' smart properties and how biocomposite materials are manufactured by cells provides not only bio-inspiration for new classes of smart actuators and sensors but also foundational technology for smart materials and their manufacture. In this case study, I examine the unique smart properties of bone, which are evident at multiple length scales and how they provide inspiration for novel classes of mechanoactive materials. I then review potential approaches to engineer and manufacture bioinspired smart materials that can be applied to solve currently intractable problems such as the need for "smart" body armor or decor cum personal safety devices.