Janus Film Research Articles

Photo-induced Janus effect of graphene oxide films

The effect of UV irradiation on the wettability of GO films, as well as the possibility of making a film with different properties of its surface, the Janus film, has been studied. The O/C ratio changes from 0.32 to 0.26 after 6 ​h of UV irradiation. The contact angle of water droplet wetting on an unirradiated surface is θ ​≈ ​35°. The contact angle reaches more than 95° on the irradiated surface, which means that a hydrophobic surface on a film can be obtained. The origin of amphiphilic properties of the GO film are associated with the photochemical reduction of GO.

Mo Scarpelli, director. Anbessa. 2019. 85 minutes. Amharic. Ethiopia. Rake Films. Vimeo, rent $3.99, purchase $8.99. - Jessica Beshir, director. Faya Dayi. 2021. 120 minutes. Oromiffa and Harari. Ethiopia. Merkhana Films. Distributed by MUBI and on Criterion by Janus Films

Mo Scarpelli, director. Anbessa. 2019. 85 minutes. Amharic. Ethiopia. Rake Films. Vimeo, rent 8.99. - Jessica Beshir, director. Faya Dayi. 2021. 120 minutes. Oromiffa and Harari. Ethiopia. Merkhana Films. Distributed by MUBI and on Criterion by Janus Films - Volume 64 Issue 4

Gold Nanoparticles Monolayer Doping PEDOT : PSS Janus Film for Hydrogen Sulfide Sensor

AbstractAuNPs monolayer doping Poly(3,4‐ethylenedioxythiophene):polystyrenesulfonate (PEDOT : PSS) film on interdigitated electrode had been fabricated into AuNPs/PEDOT : PSS Janus film sensor to detect hydrogen sulfide (H2S). The results show that the Janus film sensors have a wide measurement range of H2S concentration. The sensitivity of PEDOT : PSS/AuNPs sensor grows up with the thickness of Janus film increases. The resistance response of AuNPs Janus film was affected little by the rough surface states of PEDOT : PSS film. In addition, the PEDOT : PSS/AuNPs film sensor had been used again to detect H2S. This work presents a platform to inspire a novel high sensitive chemiresistive sensor via nanoparticles monolayer.

Elastic Janus film for Wound Dressings: Unidirectional Biofluid Transport and Effectively Promoting Wound Healing

AbstractThe intrinsic hydrophilicity of conventional dressings cannot achieve effective management of excessive biofluid around the wound bed, which inevitably causes infection and hinders wound healing. In addition, present dressings such as medical gauze or band aids have a limited stretching capability, which does not comply well with the skin deformation during muscle movement, thus impacting patient comfort. Herein, a Janus wound dressing is reported by assembling an external hydrophobic (HP) adhesive tape, a filter paper, and a polydimethylsiloxane (PDMS) Janus film. The PDMS Janus film as the primary dressing can unidirectionally remove biofluid away from the wound bed. The mechanism of the unidirectional biofluid transport is investigated, demonstrating that the stretching or bending of the Janus dressing is beneficial for unidirectional biofluid draining. It indicates that the Janus PDMS film has potential for practical applications on stretched or bended skin surface. In addition, in order to prevent bacterial infection, amoxicillin powder is uniformly encapsulated on the HP layer of Janus film, resulting in faster wound healing. This study is valuable for designing and fabricating next‐generation dressings with high performance for clinical applications.

Novel photosensitive dual-anisotropic conductive Janus film endued with magnetic-luminescent properties and derivative 3D structures

A new photosensitive dual-anisotropic conductive Janus film (PDCJF) is proposed for the first time. It is rationally designed and manufactured by facile electrospinning. PDCJF is firstly constructed using 2,7-dibromo-9-fluorenone (DBF) with photoconductive and luminescent properties. Janus nanofibers are respectively used as the building units to construct the top layer (T-PDCJF) and the bottom layer (B-PDCJF) of PDCJF. The two layers are tightly bonded to form PDCJF. Under light irradiation, there is photosensitive dual-anisotropic conduction in PDCJF, but there is no anisotropic conduction without light. Thus, the transition of PDCJF from mono-functional magnetism to tri-functionalities is realized under light and without light. The luminescence color of PDCJF is tunable and it emits white-light. This is made possible by modulating the amounts of luminescent substances and excitation wavelength. The microscopic Janus nanofibers used as building units and macroscopic Janus film structure ensure high photosensitive dual-anisotropic conduction and excellent fluorescence in PDCJF. The two-dimensional (2D) PDCJF is rolled to obtain three-dimensional (3D) Janus-type tubes and 2D plus 3D complete flag-like structures with exceptional multi-functionalities. The new findings can strongly guide in developing advanced multi-functional nanostructures.

Cotton cloth supported tungsten carbide/carbon nanocomposites as a Janus film for solar driven interfacial water evaporation

The enhanced water evaporation performance of our Janus films benefits from rational structure design and chemical composition modulation simultaneously.

Smart MXene-Based Janus films with multi-responsive actuation capability and high electromagnetic interference shielding performances

Smart electromagnetic interference shielding materials with multi-responsive actuation capability are greatly required for next-generation electronics. Here, a flexible, multi-responsive and electrically conductive graphene oxide (GO)/MXene Janus film is fabricated by a scalable sequential vacuum filtration technique. The hydrophilic feature of both GO and MXene enable the formation of Janus-structured films with strong obscure interfaces, achieving multiple stimuli responses (humidity, light, and electricity) and high electromagnetic interference (EMI) shielding performances. The film actuator can be largely bent from −270° to 460° within a wide relative humidity range and exhibits sensitive and fast actuation responses to near-infrared light and electricity. Additionally, the Janus film can also act as the smart switch and soft walking robot. Furthermore, the presence of the highly conductive MXene layer provides the film with attractive EMI shielding effectiveness of 40 dB at a small thickness of 1.5 μm. As a proof-of-concept, a smart EMI shielding curtain and a stimuli-responsive EMI shielding system are assembled using the Janus film. The smart EMI shielding film could effectively tune signal transmission by stimuli to meet specific shielding needs in intelligent electronics and devices.

An Al-assisted GO/rGO Janus film: Fabrication and hygroscopic properties

In this paper, we present a novel method combining drop-casting GO dispersion with an Al-assisted partial reduction technique to fabricate a freestanding Janus GO/rGO film. The laminar structure of Janus film facilitates the diffusion pathway of water molecules efficiently. The asymmetrical oxygen content of the film promotes a significant gradient of moisture uptake in GO (hydrophilic) and rGO (hydrophobic) layers, resulting in a macroscopic deformation of the Janus film proportional to the change in relative humidity. The induced strain in the film changes the resistance of the rGO film, which systematically varies as a function of the strain amplitude or equivalently the change in relative humidity. In the range of relative humidity (5 to 100%), the resistance increases gradually with measurable change in response to a change in relative humidity (RH) as low as 1%, with the change being steeper at RH >85%. The results provide foundational knowledge for developing a relative humidity sensor with high sensitivity, excellent repeatability, and fast response-recovery without the complexity of the currently available interdigitated transducer-based humidity sensors.

Free-Standing 2D Janus Gold Nanoparticles Monolayer Film with Tunable Bifacial Morphologies via the Asymmetric Growth at Air-Liquid Interface.

Large scaled two-dimensional free-standing monolayer films of gold nanoparticles show distinctive optical, electrical, and chem-physical propertie making them a new class of advanced plasmonic materials differing from bulk materials and individual nanoparticles in solution. The conventional 2D gold nanoparticle films usually possess symmetric structures and identical properties of gold nanoparticles on both sides. Herein, we developed an easy and efficient approach to construct a new type of free-standing 2D gold nanoparticle monolayer film with asymmetric gold nanoparticle structures and functions, called a 2D Janus gold nanoparticle film. The remarkable feature of our method is the subsequent asymmetric growth on one side of the interfacial self-assembled gold nanoparticle monolayer film at the air-liquid interface. It is very easy to control the morphology of the Janus film by simply and precisely adjusting the size and shape of the gold nanoparticles on the top side, and selectively tuning the structure and composition on the bottom side of the film by growing gold nanoparticles or other noble metals such as Ag, Pt, and Pd. Unlike the conventionally prepared Janus films at solid substrate that require long-time etching and transfer procedures, other features of our method include the short time in which the interfacial self-assembly and the subsequent asymmetric growth are completed as well as the easily transferable property of the Janus film onto different substrates, such as quartz glass sheets, silicon wafers, and PDMS. The obtained Janus gold nanoparticle film shows asymmetric wettabilities, optical properties, and surface-enhanced Raman scattering (SERS) effects, which is promising for a range of potential applications in optical devices, sensors, and asymmetric catalysis.

Facile preparation of Janus polymer film and application in alleviating water crisis

Water scarcity has been becoming a global water crisis, which has threatened the sustainable development of world economic. In this contribution, it will be reported that Janus polymer film can help us coping with this water crisis through water collection and water evaporation suppressing. A sodium maleate grafted polypropylene (PP-g-NaMA) film was fabricated by solvent induced self-assembly, which has one side hydrophobic and the other side superhydrophilic. In addition to low cost, high performance and excellent stability, the newly developed Janus film can be used for water evaporation reduction and water collection, both with very high efficiency. The durable film can also be recycled easily after using. It is unquestionable that the new finding reported in this paper provides a new avenue to alleviate the water crisis in the world.

Asymmetric Janus adhesive tape prepared by interfacial hydrosilylation for wet/dry amphibious adhesion

Janus films with asymmetric properties on opposite sides have been widely used to facilitate energy storage, ion transport, nanofiltration, and responsive bending. However, studies on Janus films rarely involve controlling surface adhesion, either dry or wet adhesion. Herein, we report Janus adhesive tape with an asymmetrically crosslinked polydimethylsiloxane (PDMS) network prepared through an interfacial hydrosilylation strategy, realizing wet/dry amphibious adhesion on various solid surfaces. The lightly crosslinked side of the Janus adhesive tape acts as an adhesive layer with high adhesion, and the highly crosslinked side functions as a supporting layer with high mechanical strength. This Janus adhesive tape with good adhesion and mechanical properties can be dyed different colors and can act as an underwater adhesive and a skin adhesive for wearable electronic devices. This study provides a promising design model for next-generation adhesive materials and related applications.

Programmable graphene-based humidity and heat driven actuators prepared by one-step laser direct writing

Smart materials are gathering increasing attention and play important roles in intelligent actuators, among which films with Janus structure are widely used because of their intrinsic response ability. Herein, we report a highly simplified method, laser direct writing, for preparing GO (Graphene Oxide)/rGO (Reduced Graphene Oxide) Janus films. By adjusting the output power of laser, GO homogeneous films can be accurately reduced in a single step and a certain thickness can be controllably reduced to form GO/rGO Janus films. The structure and chemical composition of the resulting GO/rGO films were characterized. Their response to ambient temperature and humidity is determined experimentally. The response performance of Janus films with different thickness was tested, and the one with thickness of 15 μm performed the best. The Janus films are made into diverse actuators, including a bionic movable creeper and a grabber that can grab a leaf upon changing the humidity in a planned way. Furthermore, we designed a finger-guessing robot that can be programmed in advance and perform the predetermined actions.

Hydrophilic/Hydrophobic Interphase-Mediated Bubble-like Stretchable Janus Ultrathin Films toward Self-Adaptive and Pneumatic Multifunctional Electronics

As promising candidates for intelligent biomimetic applications similar to living organisms, smart soft materials have aroused extensive interest due to their extraordinarily designable structures and functionality. Herein, a bubble-like elastomer-based electronic skin that can be pneumatically actuated is achieved through hydrophilic/hydrophobic interphase mediated asymmetric functionalization. The asymmetric and controllable introduction of elastic polydimethylsiloxane into the carbon nanotube film at the air/water interface can endow the Janus ultrathin film with tunable conductivity, self-adhesivity, self-adaptivity, and even self-sealing properties. As a result, the Janus films can be employed as multifunctional electronics, including self-adhesive strain sensing/thermal managing devices and even noncontact mechanical sensors as artificial eardrums for tiny air-pressure detection. Significantly, these excellent features can further enable the integration of actuating and sensing functions. As a proof of concept, the Janus film can serve as a self-supported device to simultaneously imitate the controllable contracting/expanding behaviors of the vocal sac of frog and monitor the real-time current change in this process, demonstrating significant potential in smart bionic applications.

Programmable Electrofabrication of Porous Janus Films with Tunable Janus Balance for Anisotropic Cell Guidance and Tissue Regeneration

AbstractJanus films with controlled pore structures can be particularly important in diverse applications. There remains a challenge for simple, rapid, and scalable fabrication methods to control Janus balance (JB) including the thickness of the individual face as well as porosity and pore size. Here the electrofabrication of a porous Janus film with controlled Janus balance from aminopolysaccharide chitosan under the salt effect is reported. Sequential deposition of chitosan under programmable salt environment and electrochemical conditions enables construction of Janus films with precisely controlled Janus balance. Bioactive partially soluble calcium phosphate (CaP) salts can also generate porous structure in Janus film. It is specifically reported that a chitosan/hydroxyl apatite (HAp) composite Janus film can serve as an effective scaffold for guided bone regeneration. The dense layer functions to provide mechanical support and serves as a barrier for fibrous connective tissue penetration. The porous composite layer functions to provide the microenvironment for osteogenesis. In vivo studies using a rat calvarial defect model confirm the beneficial features of this Janus composite for guided bone regeneration. These results suggest the potential of electrofabrication as a simple and scalable platform technology to tune the self‐organization of soft matter for a range of emerging applications.

Janus Soft Actuators with On–Off Switchable Behaviors for Controllable Manipulation Driven by Oil

Soft actuators have tremendous applications in diverse fields. Facile preparation, rapid actuation, and versatile actions are always pursued when developing new types of soft actuators. In this paper, we present a facile method integrating laser etching and mechanical cutting to prepare Janus actuators driven by oil. A Janus film with superhydrophobic and hydrophobic sides was fabricated successfully. By cutting the functional layer at the desired positions, a number of quintessential oil-driven soft devices were demonstrated. Furthermore, Janus actuators with surfaces of different wettabilities exhibited different swelling behaviors, and different media manifested different surface extensions; thus, these actuators are promising candidates for soft actuators and also realized on-off switchability between an oil/water mixture and ethanol. This study offers novel insight into the design of soft actuators, and this insight may be helpful for developing an oil-driven soft actuator that can be operated like a human finger to manipulate any object and extending stimuli-responsive applications for soft robotics.

Modularization design philosophy for multifunctional materials: a case study of a Janus film affording concurrent electrically conductive anisotropic-magnetic-fluorescent multifunctionality

A modularization design philosophy inspired by Rubik's Cube for the construction of multifunctional materials is proposed with 4M-EMF Janus film as a case study.

Self-assembled ultrathin film of CNC/PVA–liquid metal composite as a multifunctional Janus material

A new way to fabricate asymmetric, flexible, and ultrathin liquid metal Janus films with electrical, optical, and thermal anisotropies is demonstrated.

A Hydrophilic/Hydrophobic Janus Inverse-Opal Actuator via Gradient Infiltration.

Janus/gradient actuating materials have become promising candidates for actuating devices. The fabrication of functional Janus gradient actuators remains a challenge. This paper presents a facile fabrication of a hydrophilic/hydrophobic Janus inverse opal actuator via gradient infiltration. The Janus characteristics of the fabricated actuator were attributed to gradient infiltration along the thickness of the film caused by the gradient light intensity and the distinct polymerization behavior of ionic liquids and methyl methacrylate in the methanol system. The Janus film demonstrated directional bending upon water vapor adsorption, with a bending angle approaching 1440° in 4 s, accompanied by structure color/optic signal alteration. The actuating behaviors were effectively modulated by changing the composition of the film and the solvent system. Promising applications of this Janus solvent actuator were demonstrated in two sets of tests: driving an engine and lifting cargo. This work provides insight into the design and fabrication of multifunctional humidity-actuating materials.

Unconventional Janus Properties of Enokitake-like Gold Nanowire Films.

We report on unconventional Janus material properties of vertically aligned gold nanowire films that conduct electricity and interact with light and water in drastically different ways on its two opposing sides. These Janus-like properties originate from enokitake-like nanowire structures, causing the nanoparticle side ("head") to behave like bulk gold, yet the opposing nanowire side ("tail") behaves as discontinuous nanophases. Due to this Janus film structure, its head side is hydrophilic but its tail side is hydrophobic; its head side reflects light like bulk gold, yet its tail side is a broadband superabsorber; its tail side is less conductive but with tunable resistance. More importantly, the elastomer-bonded Janus film exhibits unusual mechatronic properties when being stretched, bent, and pressed. The tail-bonded elastomeric sheet can be stretched up to ∼800% strain while remaining conductive, which is about 10-fold that of head-bonded film. In addition, it is also more sensitive to bending forces and point loads than the corresponding tail-bonded film. We further demonstrate the versatility of nanowire-based Janus films for pressure sensors using bilayer structures in three different assembly layouts.

PH-Responsive Janus Film Constructed with Hydrogen-Bonding Assembly and Dopamine Chemistry.

Poly(acrylic acid) (PAA) was partially grafted with dopamine (PAA-dopa), and then layer-by-layer assembled with poly(vinylpyrrolidone) (PVPON) to prepare hydrogen-bonded (PVPON/PAA-dopa) n film. Polydopamine (PDA) was deposited on (PVPON/PAA-dopa) n film in the presence of oxidant, and hence the whole (PVPON/PAA-dopa) nPDA film was cross-linked. (PVPON/PAA-dopa) nPDA could be utilized as a platform to produce the free-standing Janus film because of the easy detaching process and various chemical reactivity of PDA layer. Ag nanoparticles were formed on (PVPON/PAA-dopa) nPDA film by electroless metallization. 1 H,1 H,2 H,2 H-Perfluorodecanethiol (PFDT) was used to further modify the film through Michael addition. After detaching from the substrate, (PVPON/PAA-dopa)20PDA/Ag/PFDT exhibits reversible swelling-shrinking behavior as the pH value changes. This free-standing film shows Janus character, one side is hydrophobic, whereas the other side is hydrophilic. In addition, the hydrophobic surface exhibits a surface-enhanced Raman scattering effect, whereas the hydrophilic side does not.