Showing papers by "Vi Khanh Truong published in 2023"

Liquid Metal Coated Textiles with Autonomous Electrical Healing and Antibacterial Properties

Abstract: Conductive textiles are promising for human–machine interfaces and wearable electronics. A simple way to create conductive textiles by coating fabric with liquid metal (LM) particles is reported. The coating process involves dip-coating the fabric into a suspension of LM particles at room temperature. Despite being coated uniformly after drying, the textiles remain electrically insulating due to the native oxide that forms on the LM particles. Yet, they can be rendered conductive by compressing the textile to rupture the oxide and thereby percolate the particles. Thus, compressing the textile with a patterned mold can pattern conductive circuits on the textile. The electrical conductivity of these circuits increases by coating more particles on the textile. Notably, the conductive patterns autonomously heal when cut by forming new conductive paths along the edge of the cut. The textiles prove to be useful as circuit interconnects, Joule heaters, and flexible electrodes to measure ECG signals. Further, the LM-coated textiles provide antimicrobial protection against Pseudomonas aeruginosa and Staphylococcus aureus. Such simple coatings provide a route to convert otherwise insulating textiles into electrical circuits with the ability to autonomously heal and provide antimicrobial properties.

Graphene Nanosheets Stabilized by P3HT Nanoparticles for Printable Metal-Free Electrocatalysts for Oxygen Reduction

Abstract: The development of metal-free electrocatalysts with efficient catalytic performance and long-term stability is highly desirable for fuel cell applications. In this study, a solution-processable graphene-based electrocatalyst for the oxygen reduction reaction (ORR) is developed using a facile liquid-phase exfoliation process. An aqueous dispersion of poly(3-hexylthiophene-2,5-diyl) (P3HT) nanoparticles is prepared via a simple miniemulsion process and used as a medium for graphite exfoliation, where the interfacial interaction between P3HT nanoparticles and graphene is utilized to simultaneously stabilize the exfoliated graphene flakes and induce efficient intermolecular charge transfer to accelerate the ORR. Neutron scattering with contrast variation was carried out to study the colloidal architecture of the produced dispersions and the interactions at the interface between graphene and P3HT nanoparticles. The nanoparticle-stabilized graphene (G/P3HT) dispersions were employed for printing of flexible conductive circuits (∼180 Ω sq–1) and fabrication of metal-free electrocatalyst layers for the ORR, which reduces O2 molecules to OH– ions via the highly efficient four-electron pathway and exhibits superior stability (∼97% retention after 10,000 cycles). This printable graphene electrocatalyst provides a breakthrough in green chemistry and advanced techniques for the fabrication of low-cost and sustainable fuel cells.

Compositional Design of Surface Oxides in Gallium–Indium Alloys

Abstract: Room-temperature liquid metal alloys encompass a highly versatile family of materials possessing a unique set of chemical, electronic, biological, and mechanical properties. The surface oxide of liquid metals has a direct influence on these properties and is often composed of one of the major alloy components (i.e., gallium or indium). However, this is not a foregone conclusion, as the identity of the surface oxide can be altered by the addition of minority elements into the liquid metal. Through judicious choice of a minority alloying metal, the composition of the oxide and therefore the resulting molten alloy’s properties are significantly modified. We demonstrate this by adding a small amount (∼5%) of several thermodynamically favorable alloying elements (X = Zn, Mg, Al) to eutectic gallium indium (EGaIn), resulting in a new class of alloys with designed surface oxide compositions that we term XGaIn. Using both STEM-EDS and XPS, XGaIn alloys are shown to form oxide layers enriched in the lowest-redox element as expected based on the thermodynamics of the alloy system. This approach is shown to be generalizable across both Ga and non-Ga-based liquid metal alloy compositions. XGaIn alloys with added Zn and Mg are shown to have strong antimicrobial activity, which has exciting implications for the development of flexible electronic medical devices and sensors.

High Solubility and Bioavailability of Lobster Shell-Derived Calcium for Significantly Proliferating Bone and Skin Cells In Vitro

Abstract: Shell wastes pose environmental and financial burdens to the shellfish industry. Utilizing these undervalued shells for commercial chitin production could minimize their adverse impacts while maximizing economic value. Shell chitin conventionally produced through harsh chemical processes is environmentally unfriendly and infeasible for recovering compatible proteins and minerals for value-added products. However, we recently developed a microwave-intensified biorefinery that efficiently produced chitin, proteins/peptides, and minerals from lobster shells. Lobster minerals have a calcium-rich composition and biologically originated calcium is more biofunctional for use as a functional, dietary, or nutraceutical ingredient in many commercial products. This has suggested a further investigation of lobster minerals for commercial applications. In this study, the nutritional attributes, functional properties, nutraceutical effects, and cytotoxicity of lobster minerals were analyzed using in vitro simulated gastrointestinal digestion combined with growing bone (MG-63), skin (HaCaT), and macrophage (THP-1) cells. The calcium from the lobster minerals was found to be comparable to that of a commercial calcium supplement (CCS, 139 vs. 148 mg/g). In addition, beef incorporated with lobster minerals (2%, w/w) retained water better than that of casein and commercial calcium lactate (CCL, 21.1 vs. 15.1 and 13.3%), and the lobster mineral had a considerably higher oil binding capacity than its rivals (casein and CCL, 2.5 vs. 1.5 and 1.0 mL/g). Notably, the lobster mineral and its calcium were far more soluble than the CCS (98.4 vs. 18.6% for the products and 64.0 vs. 8.5% for their calcium) while the in vitro bioavailability of lobster calcium was 5.9-fold higher compared to that of the commercial product (11.95 vs. 1.99%). Furthermore, supplementing lobster minerals in media at ratios of 15%, 25%, and 35% (v/v) when growing cells did not induce any detectable changes in cell morphology and apoptosis. However, it had significant effects on cell growth and proliferation. The responses of cells after three days of culture supplemented with the lobster minerals, compared to the CCS supplementation, were significantly better with the bone cells (MG-63) and competitively quick with the skin cells (HaCaT). The cell growth reached 49.9–61.6% for the MG-63 and 42.9–53.4% for the HaCaT. Furthermore, the MG-63 and HaCaT cells proliferated considerably after seven days of incubation, reaching 100.3% for MG-63 and 115.9% for HaCaT with a lobster mineral supplementation of 15%. Macrophages (THP-1 cells) treated for 24 h with lobster minerals at concentrations of 1.24–2.89 mg/mL had no detectable changes in cell morphology while their viability was over 82.2%, far above the cytotoxicity threshold (<70%). All these results indicate that lobster minerals could be used as a source of functional or nutraceutical calcium for commercial products.

Printable Hydrogel Arrays for Portable and High-Throughput Shear-Mediated Assays.

Abstract: Hydrogels have been widely used to entrap biomolecules for various biocatalytic reactions. However, solute diffusion in these matrices to initiate such reactions can be a very slow process. Conventional mixing remains a challenge as it can cause irreversible distortion or fragmentation of the hydrogel itself. To overcome the diffusion-limit, a shear-stress-mediated platform named the portable vortex-fluidic device (P-VFD) is developed. P-VFD is a portable platform which consists of two main components, (i) a plasma oxazoline-coated polyvinyl chloride (POx-PVC) film with polyacrylamide and alginate (PAAm/Alg-Ca2+) tough hydrogel covalently bound to its surface and (ii) a reactor tube (L × D: 90 mm × 20 mm) where the aforementioned POx-PVC film could be readily inserted for reactions. Through a spotting machine, the PAAm/Alg-Ca2+ hydrogel can be readily printed on a POx-PVC film in an array pattern and up to 25.4 J/m2 adhesion energy can be achieved. The hydrogel arrays on the film not only offer a strong matrix for entrapping biomolecules such as streptavidin-horseradish peroxidase but are also shear stress-tolerant in the reactor tube, enabling a >6-fold increase in its reaction rate after adding tetramethylbenzidine, relative to incubation. Through using the tough hydrogel and its stably bonded substrate, this portable platform effectively overcomes the diffusion-limit and achieves fast assay detection without causing appreciable hydrogel array deformation or dislocation on the substrate film.

2‐nm‐Thick Indium Oxide Featuring High Mobility

Abstract: Thin film transistors (TFTs) are key components for the fabrication of electronic and optoelectronic devices, resulting in a push for the wider exploration of semiconducting materials and cost‐effective synthesis processes. In this report, a simple approach is proposed to achieve 2‐nm‐thick indium oxide nanosheets from liquid metal surfaces by employing a squeeze printing technique and thermal annealing at 250 °C in air. The resulting materials exhibit a high degree of transparency (>99 %) and an excellent electron mobility of ≈96 cm2 V−1 s−1, surpassing that of pristine printed 2D In2O3 and many other reported 2D semiconductors. UV‐detectors based on annealed 2D In2O3 also benefit from this process step, with the photoresponsivity reaching 5.2 × 104 and 9.4 × 103 A W−1 at the wavelengths of 285 and 365 nm, respectively. These values are an order of magnitude higher than for as‐synthesized 2D In2O3. Utilizing transmission electron microscopy with in situ annealing, it is demonstrated that the improvement in device performances is due to nanostructural changes within the oxide layers during annealing process. This work highlights a facile and ambient air compatible method for fabricating high‐quality semiconducting oxides, which will find application in emerging transparent electronics and optoelectronics.

Generation and application of four-wave mixing in collinear high harmonic generation

Abstract: We describe a thorough study of the wave-mixing procedure in the extreme ultraviolet (XUV) region involving three laser fields (800 nm, 1400 nm and 1860 nm). In addition to the phase matched HHG spectrum generated by an 800-nm laser (driving field), non-integer order wave-mixing spectra are produced when the driving field and the control field (1400 nm or 1860 nm) are collinearly focused into krypton gas. In addition, the simultaneous presence of three laser fields generates resolvable four-wave mixing (FWM) frequencies that clearly indicate the contribution of each control field. We also discuss an application of the FWM scheme to extend the HHG cutoff region and generate the XUV quasi-continuum spectrum.