Controlling autonomous propulsion of microswimmers is essential for targeted drug delivery and applications of micro/nanomachines in environmental remediation and beyond. Herein, we report two-dimensional (2D) carbon nitride-based Janus particles as highly efficient, light-driven microswimmers in aqueous media. Due to the superior photocatalytic properties of poly(heptazine imide) (PHI), the microswimmers are activated by both visible and ultraviolet (UV) light in conjunction with different capping materials (Au, Pt, and SiO₂) and fuels (H₂O₂ and alcohols). Assisted by photoelectrochemical analysis of the PHI surface photoreactions, we elucidate the dominantly diffusiophoretic propulsion mechanism and establish the oxygen reduction reaction (ORR) as the major surface reaction in ambient conditions on metal-capped PHI and even with TiO₂-based systems, rather than the hydrogen evolution reaction (HER), which is generally invoked as the source of propulsion under ambient conditions with alcohols as fuels. Making use of the intrinsic solar energy storage ability of PHI, we establish the concept of photocapacitive Janus microswimmers that can be charged by solar energy, thus enabling persistent light-induced propulsion even in the absence of illumination—a process we call “solar battery swimming”—lasting half an hour and possibly beyond. We anticipate that this propulsion scheme significantly extends the capabilities in targeted cargo/drug delivery, environmental remediation, and other potential applications of micro/nanomachines, where the use of versatile earth-abundant materials is a key prerequisite. Significance Light-driven microswimmers offer prospects for autonomous microsystems. Understanding their surface catalytic processes responsible for propulsion is essential in tailoring them for specific applications. So far, photocatalytic microswimmers have been limited by the requirement of continuous illumination. Here, we report light-driven 2D carbon nitride-based Janus microswimmers, which show efficient propulsion in aqueous media not only during but also after illumination for about 30 min after 30 s prior illumination, due to so-called solar battery swimming. Contrary to the mainstream reports, we reveal oxygen reduction rather than hydrogen evolution being responsible for propulsion with alcohol fuels. Balancing reaction conditions, we report the realization of light-induced intrinsic charging of a microswimmer, enabling sustained ballistic propulsion in the dark through discharge of accumulated energy.

Respiratory toxicology remains a major research area in the 21st century since current scenario of airborne viral infection transmission and pollutant inhalation is expected to raise the annual morbidity beyond 2 million. Clinical and epidemiological research connecting human exposure to air contaminants to understand adverse pulmonary health outcomes is, therefore, an immediate subject of human health assessment. Important observations in defining systemic effects of environmental contaminants on inhalation metabolic dysfunction, liver health, and gastrointestinal tract have been well explored with in vivo models. In this review, a framework is provided, a paradigm is established about inhalation toxicity testing in vitro, and a brief overview of breathing Lungs‐on‐Chip (LoC) as design concepts is given. The optimized bioengineering approaches and microfluidics with their fundamental pros, and cons are presented. There are different strategies that researchers apply to inhalation toxicity studies to assess a variety of inhalable substances and relevant LoC approaches. A case study from published literature and frame arguments about reproducibility as well as in vitro/in vivo correlations are discussed. Finally, the opportunities and challenges in soft robotics, systems inhalation toxicology approach integrating bioengineering, machine learning, and artificial intelligence to address a multitude model for future toxicology are discussed.

A novel hybrid nanocomposite based on a metal–organic framework (MOF) and electroconductive cellulose nanocrystals (CNCs) was developed for the individual and simultaneous detection of heavy metal ions Cd2+, Pb2+, Cu2+, and Hg2+. The reported modified electrode was based on a thin layer of the hybrid nanocomposite formed on a glassy carbon electrode via a drop-casting method. The MOF, DUT-67, provided binding sites for heavy metal ions due to putative interactions between organic linkers and metal cation analytes. The electroconductive matrix was composed of PEDOT:PSS and CNC, which not only served as an effective template for the DUT-67 MOF but also enhanced electron transfer of the hybrid nanocomposites through the interconnected network of conductive CNC/PEDOT:PSS. Following optimization of the solution pH, accumulation time, and accumulation potential, the developed hybrid nanocomposite-based electrochemical sensor was successfully applied for individual and simultaneous detection of target heavy metal ions in aqueous solutions with high sensitivity and selectivity. Under the optimized conditions, linear detection ranges of simultaneous detection of Cd2+, Pb2+, Cu2+, and Hg2+ were found to be 20–163, 20–163, 20–84, and 20–112 μg L–1, respectively, with detection limits of 2.5, 1.78, 0.226, and 0.294 μg L–1, respectively. No major interference effects were found from possible coexisting, interfering ions. This allows the practical use of the sensor to examine a variety of different aqueous environments. This study demonstrates the feasibility of our hybrid nanocomposite as a novel sensing platform for the electrochemical detection of multiple heavy metal ions.

A gold nanoparticle (AuNP) functionalized laser‐induced graphene interdigitated electrode (LIG‐IDE) is fabricated for the label‐free detection of cortisol. Self‐assembled monolayers of 3‐Mercaptopropionic acid immobilized on the AuNP functionalized LIG‐IDE are activated via carbodiimide chemistry for the binding of the anti‐cortisol antibody. The resulting immunosensor is tested for the specific detection of cortisol over the physiologic range (0.1 p m –100 n m ) in synthetic human sweat. Electrochemical impedance spectroscopy is used to measure the change in impedance due to cortisol bonding to the LIG surface. The sensor exhibits a good linear (log(concentration)) fit over the entire concentration range ( R ²  = 0.9662) and a LOD of 0.0085 n m . The minimal effect of synethtic sweat shows its potential use in real‐world applications. A specificity test against similarly structured molecules demonstrates high affinity toward cortisol. Furthermore, the developed sensor exhibits excellent reproducibility with a 5.93%RSD. Given the simple and facile processability of immunosensors, the developed label‐free AuNP functionalized LIG‐based biosensing platform shows great promise as an effective and low‐cost tool suitable for healthcare monitoring and point‐of‐care diagnostics, and it can be applied as an immunosensor for other affinity‐based biosensors.