Swimming microrobots that are energized by external magnetic fields exhibit a variety of intriguing collective behaviors, ranging from dynamic self-organization to coherent motion; however, achieving multiple, desired collective modes within one colloidal system to emulate high environmental adaptability and enhanced tasking capabilities of natural swarms is challenging. Here, we present a strategy that uses alternating magnetic fields to program hematite colloidal particles into liquid, chain, vortex, and ribbon-like microrobotic swarms and enables fast and reversible transformations between them. The chain is characterized by passing through confined narrow channels, and the herring school–like ribbon procession is capable of large-area synchronized manipulation, whereas the colony-like vortex can aggregate at a high density toward coordinated handling of heavy loads. Using the developed discrete particle simulation methods, we investigated generation mechanisms of these four swarms, as well as the “tank-treading” motion of the chain and vortex merging. In addition, the swarms can be programmed to steer in any direction with excellent maneuverability, and the vortex’s chirality can be rapidly switched with high pattern stability. This reconfigurable microrobot swarm can provide versatile collective modes to address environmental variations or multitasking requirements; it has potential to investigate fundamentals in living systems and to serve as a functional bio-microrobot system for biomedicine.

The T-1000 liquid metal terminator, which can transform and self-repair, represents a dream for decades that robots can fundamentally change our daily life. Until now, some large-scale liquid metal machines have been developed. However, there is no report on nanoscaled liquid metal machines and their biomedical applications. We describe here a shape-transformable and fusible rodlike swimming liquid metal nanomachine, based on the biocompatible and transformable liquid metal gallium. These nanomachines were prepared by a pressure-filter-template technology, and the diameter and length could be controlled by adjusting the nanoporous templates, filter time, and pressure. The as-prepared liquid gallium nanomotors display a core-shell nanorod structure composed of a liquid gallium core and solid gallium oxide shell. Upon exposure to an ultrasound field, the generated acoustic radiation force in the levitation plane can propel them to move autonomously. The liquid metal nanomachine can actively seek cancer cells and transform from a rod to a droplet after drilling into cells owing to the removal of gallium oxide layers in the acidic endosomes. These transformed nanomachines could fuse together inside cells and photothermally kill cancer cells under illumination of near-infrared light. Such acoustically propelled shape-transformable rodlike liquid metal nanomachines have great potential for biomedical applications.

Water-soluble perylenediimides (PDIs) with high fluorescence intensity, photostability and biocompatibility have been successfully prepared and applied in the biological field. In this tutorial review, we briefly focus on the synthetic strategies for the preparation of water-soluble PDIs by incorporating ionic or non-ionic substituents with multiple polar groups into the bay-region, imide- or ortho-positions of PDIs. These ionic/non-ionic substituents can suppress π-π aggregation and shield the inner perylene chromophores, thus contributing to the water solubility which is essential for biological applications. The optical properties, absorption and emission maxima above 500 nm, minimize the autofluorescence background of cells and provide access to imaging in living cells. The biological applications of water-soluble PDIs are discussed from simple (basic) to complex (advanced) processes, including biosensing in vitro studies, imaging and gene/drug delivering in living cells, tissues and the whole body. The promising future of designed multi-functional water-soluble PDIs will be highlighted in this review.

We report a magnetically actuated peanut-shaped hematite colloid motor that can not only move in a rolling or wobbling mode in fluids but also perform single cell manipulation and patterning in a noncontact way. The peanut motor in a rolling mode can reach a maximal velocity of 10.6 μm s under a rotating magnetic field of 130 Hz and 6.3 mT and achieve a more precisely controllable motion in predefined tracks. While in a wobbling mode, the motor reaches a maximal velocity of 14.5 μm s under a conical rotating magnetic field of 80 Hz and 6.3 mT and can climb over steep slopes to adapt the motor for more complex environments. The fluid flow simulation results reveal that the difference between two movement modes mostly comes from the distribution discrepancy of the flow fields near the motors. Through the integration of the rolling and wobbling movement, these peanut motors can autonomously transport and release cells to a predefined site and thus form complex cell patterns without a physical contact. Such magnetically actuated peanut colloid motors afford a biofriendly technique for manipulation and patterning of cells, cell measurements, and intracellular communication investigations.

Shape tunable liquid metal nanoparticles were fabricated with characterization of biocompatibility, favorable photothermal conversion efficiency and tumor targeting capability for photothermal therapy.