Advances in Nanoarchitectonics: A Review of "Static" and "Dynamic" Particle Assembly Methods

Particle assembly is a promising technique to create functional materials and devices from nanoscale building blocks. However, the control of particle arrangement and orientation is challenging and requires careful design of the assembly methods and conditions. In this study, the static and dynamic methods of particle assembly are reviewed, focusing on their applications in biomaterial sciences. Static methods rely on the equilibrium interactions between particles and substrates, such as electrostatic, magnetic, or capillary forces. Dynamic methods can be associated with the application of external stimuli, such as electric fields, magnetic fields, light, or sound, to manipulate the particles in a non-equilibrium state. This study discusses the advantages and limitations of such methods as well as nanoarchitectonic principles that guide the formation of desired structures and functions. It also highlights some examples of biomaterials and devices that have been fabricated by particle assembly, such as biosensors, drug delivery systems, tissue engineering scaffolds, and artificial organs. It concludes by outlining the future challenges and opportunities of particle assembly for biomaterial sciences. This review stands as a crucial guide for scholars and professionals in the field, fostering further investigation and innovation. It also highlights the necessity for continuous research to refine these methodologies and devise more efficient techniques for nanomaterial synthesis. The potential ramifications on healthcare and technology are substantial, with implications for drug delivery systems, diagnostic tools, disease treatments, energy storage, environmental science, and electronics.

Milli-scale cellular robots that can reconfigure morphologies and behaviors simultaneously

Modular robot that can reconfigure architectures and functions has advantages in unpredicted environment and task. However, the construction of modular robot at small-scale remains a challenge since the lack of reliable docking and detaching strategies. Here we report the concept of milli-scale cellular robot (mCEBOT) achieved by the heterogeneous assembly of two types of units (short and long units). Under the magnetic field, the proposed mCEBOT units can not only selectively assemble (e.g., end-by-end and side-by-side) into diverse morphologies corresponding to the unstructured environments, but also configure multi-modes motion behaviors (e.g., slipping, rolling, walking and climbing) based on the on-site task requirements. We demonstrate its adaptive mobility from narrow space to high barrier to wetting surface, and its potential applications in hanging target taking and environment exploration. The concept of mCEBOT offers new opportunities for robot design, and will broaden the field of modular robot in both miniaturization and functionalization.

Modular robots with reconfigurable architectures show advantages in unpredicted environments. Here Yang et al. propose a heterogeneous assembly concept for cellular robot construction at millimeter scales, which can simultaneously reconfigure their morphologies and behaviours to conduct versatile tasks on demand.

Multi-functionalized micro-helical capsule robots with superior loading and releasing capabilities

The functionalization of microrobots is essential for realizing their biomedical application in targeted cargo delivery, but the multifunctional integration of microrobots and controllable cargo delivery remains an enormous challenge at present. This work reports a kind of multi-functionalized micro-helical robot with superior loading capabilities for the controlled release of encapsulants. The magnetic microrobot, with a multilayer capsule helical structure, was developed via multifunctional strategies, including microfluidic synthesis, polyelectrolyte complexation, and surface coating with magnetic nanoparticles. The microrobot is constructed of a helical structure from a calcium alginate microfiber via a co-axial capillary microfluidic system. Then, it is coated with a polyelectrolyte complexation membrane and decorated with magnetic nanoparticles. After multi-step layer-by-layer (LbL) assembly with functionalized units, the structure is converted to a helical capsule possessing a soft and biocompatible polysaccharide alginate/chitosan/alginate shell with Fe₃O₄ nanoparticles decorated on the surface. The functionalized microrobot not only enables wireless steering with rotational locomotion under the control of a six degrees of freedoms (6-DOFs) electromagnetic system at different frequencies, but it also possesses stimuli-responsive abilities owing to the semi-permeable membrane, which can trigger the controllable release of encapsulants in response to ions in the environment. This work provides an efficient strategy for the superior multi-functionalization of microrobots to achieve enhanced locomotion and encapsulation performance for the loading, transport, and targeted delivery of cargo.