Microfluidic devices offer important benefits for forensic applications, in particular for fast tests at a crime scene. A large portion of forensic applications require microfluidic chip material to ...show compatibility with biochemical reactions (such as amplification reactions), and to have high transparency in the visible region and high chemical resistance. Also, preferably, manufacturing should be simple. The characteristic properties of cyclic olefin copolymer (COC) fulfills these requirements and offers new opportunities for the development of new forensic tests. In this work, the versatility of COC as material for lab-on-a-chip (LOC) systems in forensic applications has been explored by realizing two proof-of-principle devices. Chemical resistance and optical transparency were investigated for the development of an on-chip presumptive color test to indicate the presence of an illicit substance through applying absorption spectroscopy. Furthermore, the compatibility of COC with a DNA amplification reaction was verified by performing an on-chip multiple displacement amplification (MDA) reaction.
Piezocatalysis has gradually come into the limelight due to its great potential for solving energy shortages and environmental pollution problems. However, limited piezocatalytic efficiency is a ...severe bottleneck for its practical applications. Here, well‐defined BaTiO3 nanosheets with highly exposed {001} polar facets are successfully synthesized to enhance the piezocatalytic activity. The 001 piezoelectric polarization can drive the carriers to migrate to the surface along the out‐of‐plane direction. The polar surface provides abundant active sites for the piezocatalytic reaction. As a result, a superior piezocatalytic degradation ratio of organic pollutants is obtained with a high first‐order rate constant k of 0.0835 min−1, which is 2.7 times higher than the BaTiO3 nanoparticles. Furthermore, BaTiO3 nanosheets display an outstanding H2 production capability, with the rate of 305 µmol g−1 h–1, which is almost two times higher than that of BaTiO3 nanoparticles. This work thus provides a novel and comprehensive strategy for designing high‐performance piezocatalysts with an out‐of‐plane polarization, and also provides novel insights for the optimization of the piezocatalytic activity by regulating the polar facet of piezocatalysts.
Regular BaTiO3 nanosheets with highly exposed {001} facets are successfully synthesized. Compared with nanoparticles, these nanosheets exhibit enhanced piezocatalytic performance for pollutant degradation and H2 production, thanks to their out‐of‐plane polarization and abundant active sites on the large exposed surface. This work provides an efficient route for improving piezocatalytic activity by tuning the exposed crystalline facets.
Piezo-photocatalysis has emerged as a promising strategy to address environmental pollution and the fast-growing energy shortage. Unfortunately, current efficiencies of piezo-photocatalysts are still ...far from ideal, and improving their catalytic efficiency remains challenging. In this paper, we introduce oxygen vacancies (OVs) in Bi4Ti3O12 (BIT) nanosheets to boost their piezo-photocatalytic performance. Compared to pristine BIT nanosheets, BIT with an optimized OV concentration exhibit excellent piezo-photocatalytic activity, with an enhancement of 2.2 times the degradation rate constant (k = 0.214 min−1) for Rhodamine B (RhB). The effect of OVs on the adsorption energy and Bader charges was also investigated using density functional theory (DFT) calculations, which shed light on the underlying mechanism that improves the piezo-photocatalytic process in the presence of OVs. Specifically, the introduction of OVs increases the adsorption energy and Bader charges, resulting in an enhancement of charge transfer between O2/H2O and BIT, thus facilitating the catalytic process. This study provides a deeper understanding into the regulation mechanism of OV enhanced piezo-photocatalytic activity and opens new avenues for designing high-performance piezo-photocatalysts.
Display omitted
•Bi4Ti3O12 nanosheets with different OV concentration were prepared.•Piezo-photocatalytic performance of Bi4Ti3O12 nanosheets was significantly improved with oxygen vacancy engineering.•The mechanism of OV enhanced piezo-photocatalytic activity was investigated and revealed.
Microrobots
In article number 2310084, Salvador Pané, Minsoo Kim, Hao Ye, and co‐workers introduce microrobotic superstructures comprising a magnetic gelatin composite chassis threaded with iron ...helical micromachines. Magnetic inputs can be used to navigate the superstructure (gradients) and also dissolve the chassis through magnetic hyperthermia, thereby releasing the micromachines to navigate through narrow channels. The capability of these micromachines to disassemble on‐command to access narrower conduits enhances the microrobots' multifunctionality.
Abstract
Piezocatalysis has gradually come into the limelight due to its great potential for solving energy shortages and environmental pollution problems. However, limited piezocatalytic efficiency ...is a severe bottleneck for its practical applications. Here, well‐defined BaTiO
3
nanosheets with highly exposed {001} polar facets are successfully synthesized to enhance the piezocatalytic activity. The 001 piezoelectric polarization can drive the carriers to migrate to the surface along the out‐of‐plane direction. The polar surface provides abundant active sites for the piezocatalytic reaction. As a result, a superior piezocatalytic degradation ratio of organic pollutants is obtained with a high first‐order rate constant
k
of 0.0835 min
−1
, which is 2.7 times higher than the BaTiO
3
nanoparticles. Furthermore, BaTiO
3
nanosheets display an outstanding H
2
production capability, with the rate of 305 µmol g
−1
h
–1
, which is almost two times higher than that of BaTiO
3
nanoparticles. This work thus provides a novel and comprehensive strategy for designing high‐performance piezocatalysts with an out‐of‐plane polarization, and also provides novel insights for the optimization of the piezocatalytic activity by regulating the polar facet of piezocatalysts.
Abstract
The past decade has seen an upsurge in the development of small‐scale magnetic robots for various biomedical applications. However, many of the reported designs comprise components with ...biocompatibility concerns. Strategies for fabricating biocompatible and degradable microrobots are required. In this study, polyvinyl alcohol (PVA)‐based magnetic hydrogel microrobots with different morphologies and tunable stability are developed by combining a 3D printed template‐assisted casting with a salting‐out process. 3D sacrificial micromolds are prepared via direct laser writing to shape PVA‐magnetic nanoparticle composite hydrogel microrobots with high architectural complexity. By adjusting the PVA composition and salting‐out parameters, the hydrogel dissolubility can be customized. Due to their high mobility, tunable stability, and high biocompatibility, these PVA‐based magnetic microrobots are suitable platforms for targeted drug and cell delivery.
Sugars are ubiquitous in food, and are among the main sources of energy for almost all forms of life. Sugars can also form structural building blocks such as cellulose in plants. Because of their ...inherent degradability and biocompatibility characteristics, sugars are compelling materials for transient devices. Here, an additive manufacturing approach for the production of magnetic sugar‐based composites is introduced. First, it is shown that sugar‐based 3D architectures can be 3D printed by selective laser sintering. This method enables not only the caramelization chemistry but also the mechanical properties of the sugar architectures to be adjusted by varying the laser energy. It is also demonstrated that mixtures of sugar and magnetic particles can be processed as 3D composites. As a proof of concept, a sugar‐based millimeter‐scale helical swimmer, which is capable of corkscrew motion in a solution with a viscosity comparable to those of biological fluids, is fabricated. The millirobot quickly dissolves in water, while being manipulated through magnetic fields. The present fabrication method can pave the way to a new generation of transient sugar‐based small‐scale robots for minimally invasive procedures. Due to their rapid dissolution, sugars can be used as an intermediate step for transporting swarms of particles to specific target locations.
Sugars are among the main sources of energy and structural building blocks for almost all forms of life. Because of their degradability and biocompatibility, sugars are compelling materials in transient devices and robotics. An additive manufacturing approach for the production of 3D sugar‐based composites is introduced, which can pave the way for a new generation of transient small‐scale devices.
Magnetic fields have been regarded as an additional stimulus for electro‐ and photocatalytic reactions, but not as a direct trigger for catalytic processes. Multiferroic/magnetoelectric materials, ...whose electrical polarization and surface charges can be magnetically altered, are especially suitable for triggering and control of catalytic reactions solely with magnetic fields. Here, it is demonstrated that magnetic fields can be employed as an independent input energy source for hydrogen harvesting by means of the magnetoelectric effect. Composite multiferroic CoFe2O4–BiFeO3 core–shell nanoparticles act as catalysts for the hydrogen evolution reaction (HER), which is triggered when an alternating magnetic field is applied to an aqueous dispersion of the magnetoelectric nanocatalysts. Based on density functional calculations, it is proposed that the hydrogen evolution is driven by changes in the ferroelectric polarization direction of BiFeO3 caused by the magnetoelectric coupling. It is believed that the findings will open new avenues toward magnetically induced renewable energy harvesting.
The hydrogen evolution reaction (HER) is initiated by exploiting the magnetoelectric nature of CoFe2O4–BiFeO3 core–shell nanoparticles purely with alternating magnetic fields. As a direct trigger for the HER, magnetic fields can open cooperative pathways for maximizing hydrogen production by synergetic combinations with other energy sources such as electric fields and light.
Magnetic microrobots have been developed for navigating microscale environments by means of remote magnetic fields. However, limited propulsion speeds at small scales remain an issue in the ...maneuverability of these devices as magnetic force and torque are proportional to their magnetic volume. Here, a microrobotic superstructure is proposed, which, as analogous to a supramolecular system, consists of two or more microrobotic units that are interconnected and organized through a physical (transient) component (a polymeric frame or a thread). The superstructures consist of microfabricated magnetic helical micromachines interlocked by a magnetic gelatin nanocomposite containing iron oxide nanoparticles (IONPs). While the microhelices enable the motion of the superstructure, the IONPs serve as heating transducers for dissolving the gelatin chassis via magnetic hyperthermia. In a practical demonstration, the superstructure's motion with a gradient magnetic field in a large channel, the disassembly of the superstructure and release of the helical micromachines by a high‐frequency alternating magnetic field, and the corkscrew locomotion of the released helices through a small channel via a rotating magnetic field, is showcased. This adaptable microrobotic superstructure reacts to different magnetic inputs, which can be used to perform complex delivery procedures within intricate regions of the human body.
A magnetically driven microrobotic superstructure is designed for navigation in microscale environments. The superstructure consists of microhelices interlocked with a gelatin composite chassis containing iron oxide nanoparticles. The helices serve as the motion component, while the nanoparticles enable the gelatin to dissolve via magnetic hyperthermia. Upon dissolution, the helices are released and navigate through smaller conduits using a rotating field.
Soft materials play a crucial role in small-scale robotic applications by closely mimicking the complex motion and morphing behavior of organisms. However, conventional fabrication methods face ...challenges in creating highly integrated small-scale soft devices. In this study, we leverage microfluidics to precisely control reaction-diffusion (RD) processes to generate multifunctional and compartmentalized calcium-cross-linkable alginate-based microfibers. Under RD conditions, we produce sophisticated alginate-based fibers for magnetic soft continuum robotics (mSCR) applications with customizable features, such as geometry (compact or hollow), degree of cross-linking, and the precise localization of magnetic nanoparticles (inside the core, surrounding the fiber, or on one side). This fine control allows for tuning the stiffness and magnetic responsiveness of the microfibers. Additionally, chemically cleavable regions within the fibers enable disassembly into smaller robotic units or roll-up structures under a rotating magnetic field. These findings demonstrate the versatility of microfluidics in processing highly integrated small-scale devices. This article is protected by copyright. All rights reserved.
PDF
