Needle-and-syringe-based delivery has been the commercial standard for vaccine administration to date. With worsening medical personnel availability, increasing biohazard waste production, and the possibility of cross-contamination, we explore the possibility of biolistic delivery as an alternate skin-based delivery route. Delicate formulations like liposomes are inherently unsuitable for this delivery model as they are fragile biomaterials incapable of withstanding shear stress and are exceedingly difficult to formulate as a lyophilized powder for room temperature storage. Here we have developed a approach to deliver liposomes into the skin biolistically—by encapsulating them in a nano-sized shell made of Zeolitic Imidazolate Framework-8 (ZIF-8). When encapsulated within a crystalline and rigid coating, the liposomes are not only protected from thermal stress, but also shear stress. This protection from stressors is crucial, especially for formulations with cargo encapsulated inside the lumen of the liposomes. Moreover, the coating provides the liposomes with a solid exterior that allows the particles to penetrate the skin effectively. In this work, we explored the mechanical protection ZIF-8 provides to liposomes as a preliminary investigation for using biolistic delivery as an alternative to syringe-and-needle–based delivery of vaccines. We demonstrated that liposomes with a variety of surface charges could be coated with ZIF-8 using the right conditions, and this coating can be just as easily removed—without causing any damage to the protected material. The protective coating prevented the liposomes from leaking cargo and helped in their effective penetration when delivered into the agarose tissue model and porcine skin tissue.
Silver nanowires have a wide range of potential applications in stretchable and transparent electronics due to their excellent electrical, mechanical, and optical properties. For a successful application in electronic devices, evaluating the electrical reliability of these nanowires is required. We have studied experimentally the behavior of current density at failure for penta-twinned silver nanowires with diameters between 53 nm and 173 nm, for 93 samples. The current densities at failure are widely scattered, have an average of 9.7 x 10^7 A/cm^2 , and a standard deviation of 2.96 x 10^7 A/cm^2. Heat- transfer modelling is employed to explain the results, and Weibull statistics are used to quantify failure probabilities, thus offering guidelines for future designs based on these nanowires. The scatter observed in the measurements is attributed to surface-roughness variations among samples, which lead to local hot-spots of high current density. These results quantify the Joule-heating electrical reliability of silver nanowires and highlight the importance of heat transfer in increasing it.
Photovoltaic (PV) cells are known for poor efficiency within the range of only 6-15%, depending on the type of cells. As a result, those can convert only a small part of the absorbed solar energy into electricity, the rest is wasted as heat, which also contributes to rise in cell temperature. This heating up is undesirable for PV cells because it further decreases the electrical conversion efficiency. One viable solution to this problem is the combination of PV cells with integrated thermal collectors, known as photovoltaic-thermal (PVT) collectors. This combination usually improves the PV module efficiency compared to stand-alone PV modules, because the fluid circulating underneath the PV cells removes the heat from the cells and cools them. Among the studies concerning PVT, Delisle [1] provided a good mathematical model, where the electrical output was calculated simply by considering a linear dependence of PV efficiency with cell temperature. In the current study, following the Delisle's approach [1], a simple model configuration consisting of transpired collector absorber plate of corrugated type mounted underneath the PV cells is analyzed. The resulting mathematical system is solved numerically using multivariate Newton's method. To calculate the model output more accurately, a sophisticated model known as two-diode model is incorporated. This model provides currentvoltage characteristics with maximum power point (MPP) tracker, and considers nonlinear temperature effect. The comparison of the model outputs with experimental data reveals that two-diode model behaves differently for different sets of data at different conditions.
Pulsed light aided thin film de-wetting process to fabricate nano-patterned array is introduced. Being compared to thermal annealing process, highly intense pulsed light with millisecond duration plays a role to transform solid-state thin-film to metastable and provides enough energy as a driving force to form island-like pattern. Topological analysis using SEM and AFM was performed to confirm fabricated structures. In addition, optical performance regarding surface-plasmon resonance and light absorption was studied by experimental UV-VIS spectroscopy and computer aided electromagnetics (EM) simulation. This research will benefit to the real-time roll-to-roll fabrication for the fabrication of nanostructures without using of thermal soaking and vacuum process.
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