Active colloids show non-equilibrium behavior that departs from classical Brownian motion, thus providing a platform for novel fundamental phenomena and for enticing possible applications ranging from water treatment to medicine and microrobotics. Although the physics, motion mechanisms and guidance have been extensively investigated, active colloids are rarely exploited to simultaneously guide and transport micron-sized objects in a controllable and reversible manner. Here, we use autonomous active Janus particles as colloidal shuttles to controllably transport cargo at the microscale using external electric and magnetic fields. The active motion arises from the metallodielectric characteristics of the Janus particles, which allows them to also trap, transport and release cargo particles through dielectrophoretic interactions induced by an AC electric field. The ferromagnetic nature of the nickel layer that forms the metallic hemisphere of the Janus colloids provides an additional mechanism to direct the motion of the shuttle using an external magnetic field. With this highly programmable colloidal system, we are able to harness active colloid motion and use it to transport cargo particles to specific destinations through a pre-defined route. A simple analytical model is derived to successfully describe the motion of the shuttle-cargo assembly in response to the applied electrical field. The high level of control on cargo pick-up, transport and release leads to a powerful delivery tool, which could eventually be used in microactuators, microfluidics or for controlled delivery within organ-on-a-chip devices.

One of the major challenges in modern robotics is controlling micromanipulation by active and adaptive materials. In the respiratory system, such actuation enables pathogen clearance by means of motile cilia. While various types of artificial cilia have been engineered recently, they often involve complex manufacturing protocols and focus on transporting liquids only. Here, soft magnetic carpets are created via an easy self‐assembly route based on the Rosensweig instability. These carpets can transport not only liquids but also solid objects that are larger and heavier than the artificial cilia, using a crowd‐surfing effect.This amphibious transportation is locally and reconfigurably tunable by simple micromagnets or advanced programmable magnetic fields with a high degree of spatial resolution. Two surprising cargo reversal effects are identified and modeled due to collective ciliary motion and nontrivial elastohydrodynamics. While the active carpets are generally applicable to integrated control systems for transport, mixing, and sorting, these effects can also be exploited for microfluidic viscosimetry and elastometry.

Ecologically friendly wood electronics will help alleviating the shortcomings of state-of-art cellulose-based “green electronics”. Here we introduce iron-catalyzed laser-induced graphitization (IC-LIG) as an innovative approach for engraving large-scale electrically conductive structures on wood with very high quality and efficiency, overcoming the limitations of conventional LIG including high ablation, thermal damages, need for multiple lasing steps, use of fire retardants and inert atmospheres. An aqueous bio-based coating, inspired by historical iron-gall ink, protects wood from laser ablation and thermal damage while promoting efficient graphitization and smoothening substrate irregularities. Large-scale (100 cm2), highly conductive (≥2500 S m−1) and homogeneous surface areas are engraved single-step in ambient atmosphere with a conventional CO2 laser, even on very thin (∼450 µm) wood veneers. We demonstrate the validity of our approach by turning wood into highly durable strain sensors, flexible electrodes, capacitive touch panels and an electroluminescent LIG-based device.

Structural color is frequently exploited by living organisms for biological functions and has also been translated into synthetic materials as a more durable and less hazardous alternative to conventional pigments. Additive manufacturing approaches were recently exploited for the fabrication of exquisite photonic objects, but the angle-dependence observed limits a broader application of structural color in synthetic systems. Here, we propose a manufacturing platform for the 3D printing of complex-shaped objects that display isotropic structural color generated from photonic colloidal glasses. Structurally colored objects are printed from aqueous colloidal inks containing monodisperse silica particles, carbon black, and a gel-forming copolymer. Rheology and Small-Angle-X-Ray-Scattering measurements are performed to identify the processing conditions leading to printed objects with tunable structural colors. Multimaterial printing is eventually used to create complex-shaped objects with multiple structural colors using silica and carbon as abundant and sustainable building blocks.