Biomass is currently one of the world’s major renewable energy sources. Biomass in a
powder form has been recently proposed as the most encouraging of biomass contours, especially
because it burns like a gas. In the current study, biomass powder was examined, for the first time,
as a direct solid fuel in internal combustion engines. The aim of the current study was to investigate
modeling tools for simulation of biomass powder in combustion engines (CE). The biomass powder
applied was in a micro-scale size with a typical irregular shape; the powder length was in the range
of 75?5800 m, and the diameter was in the range 30?1380 m. Dierent mechanisms for biomass
powder drying and devolatilization/gasification were proposed, including dierent schemes’ and
mechanisms’ rate constants. Acomparison between the proposed models and experiments was carried
out and results showed good matching. Nevertheless, it is important that a biomass powder simulation
addresses overlapping/complicated sub-process. During biomass powder combustion, tar was shown
to be formed at a rate of 57 wt.%, and, accordingly, the formation and thermal decomposition
of tar were modelled in the study, with the results demonstrating that the tar was formed and
then disintegrated at temperatures between 700 and 1050 K. Through biomass powder combustion,
moisture, tar, and gases were released, mostly from one lateral of particles, which caused ejection of
the solid particles. These new phenomena were investigated experimentally and modeled as well.
Results also showed that all the proposed models, along with their rate constants, activation energies,
and other models’ parameters, were capable of reproducing the mass yields of gases, tar, and char at a
wide range of working temperatures. The results showed that the gasification/devolatilization model
3 is somewhat simple and economical in the simulation/computation scheme, however, models 1 and
2 are rather computationally heavy and complicated.

In recent years, the use of solar energy has been growing exponentially and applied in a wider range of
applications; one of the important applications for using solar energy is water desalination. The current
work investigates the proof of concept experimental setup for a novel solar multi-effect distillation
(MED) using alternate storage tanks. The experimental setup consists of a MED unit, two thermal
storage tanks, and a solar collector. One storage tank is used as a charging tank while the other tank is
used as a discharging tank. This unique dual-tank system stores the thermal energy to be used later in
the MED unit, which improves the control of the water mass flow rate and water temperature
throughout the MED process. The peak temperature achieved every day in the charging tank
determines the MED production capacity. This system is designed for the tanks to alternate roles every
24 hours. The testing of this design was carried out during May 2019 in Saudi Arabia. The experimental
results prove the novel concept design to work efficiently providing an average production rate of about
21 kg/day with total solar collector area of 2.7 m2 and average daily performance ratio of 2.5.

Skin damage exposes the underlying layers to bacterial invasion, leading to skin and soft tissue infections. Several pathogens have developed resistance against conventional topical antimicrobial treatments and rendered them less effective. Recently, several nanomedical strategies have emerged as a potential approach to improve therapeutic outcomes of treating bacterial skin infections. In the current study, nanofibers were utilized for topical delivery of the antimicrobial drug vancomycin and evaluated as a promising tool for treatment of topical skin infections. Vancomycin-loaded nanofibers were prepared via electrospinning technique, and vancomycin-loaded nanofibers of the optimal composition exhibited nanosized uniform smooth fibers (ca. 200 nm diameter), high drug entrapment efficiency and sustained drug release patterns over 48 h. In vitro cytotoxicity assays, using several cell lines, revealed the biocompatibility of the drug-loaded nanofibers. In vitro antibacterial studies showed sustained antibacterial activity of the vancomycin-loaded nanofibers against methicillin-resistant Staphylococcus aureus (MRSA), in comparison to the free drug. The nanofibers were then tested in animal model of superficial MRSA skin infection and demonstrated a superior antibacterial efficiency, as compared to animals treated with the free vancomycin solution. Hence, nanofibers might provide an efficient nanodevice to overcome MRSA-induced skin infections and a promising topical delivery vehicle for antimicrobial drugs.

Channel-based microfluidics was proven to be a helpful platform for reproducible preparation of nanoparticles (NPs), where controlled mixing of fluids allows homogeneous and tuned process of NPs formation. Nanoprecipitation is a popular method for polymeric NPs formation based on controlled precipitation of a polymer upon mixing of two miscible solvents. Conventionally, flow rate, flow rate ratio and polymer concentration have been utilized to control NPs size and polydispersity. However, minimum attention has been given to the effect of channel geometry on nanoprecipitation process. In our study, we investigated the effect of channel geometry and design on the size and polydispersity index (PDI) of poly (lactic-co-glycolic) acid (PLGA) NPs. Ten different designs with varied channel length, aspect ratio, number of interfaces and channel curvature were fabricated and tested. These variations were introduced to modify the diffusion rate, the interface area or to introduce Dean flow, all of which will change the mixing time (τmix). The effects of these variations were compared to that of different flow parameters. Change in channel length did not have a significant effect on particle size. However, increasing the diffusion area and reducing τmix significantly reduced NPs’ size. Moreover, when curvature was introduced into the channel, mixing was enhanced, and particle size was decreased in a manner dependent on the velocity of the generated Dean flow. While different flow parameters continue to be the main approach for adjusting NPs properties, we demonstrate that channel geometry modification enables tuning of NPs’ size using simple designs that can be easily adapted.

With the advance of miniaturization technology, more and more electronic components are placed onto small electronic chips. This leads to the generation of high amounts of thermal energy that should be removed for the safe operation of these electronic components. Microchannel heat sinks, where electronic chips are liquid cooled instead of the conventional air cooling techniques, were proposed as a means to improve cooling rates. Later on, double layer micro channel heat sinks were suggested as an upgrade to single layer microchannel heat sinks with a better thermal performance. In the present study the effects of increasing the number of layers of the microchannel heat sink to three-layers as well as the effect of changing the flow arrangements (counter and parallel flows) within the three channel layers on the thermal performance of the heat sink were investigated. In all investigated cases the temperature distribution over the base of the microchannel heat sink system and the total pressure drop are reported. A range of mass flow rates from 1×10⁻⁴ to 5×10⁻⁴ kg/s was considered. Uniform heat flux conditions were considered during the study. COMSOL Multiphysics finite element package was employed for the numerical analysis. Results indicate significant enhancement in the uniformity of the temperature on the processor surface when multi-layer channels were employed, compared to the single-layer case. The uniformity in the temperature distribution was accompanied by reduction of pressure drop across channels for the same mass flow rate and heat flux conditions. The counter flow arrangement showed the best temperature distribution with the uniform heat flux cases.

We report optimization of geometric and flow parameters affecting size and uniformity of PLGA (poly lacticco-glycolic acid) nanoparticles (NPs) prepared inside a microchannel via nanoprecipitation. The parameters studied were microchannel geometry, flow rate and flow configurations (number of interfaces between water and solvent streams). In addition to the flow rate ratio (FRR), which had the highest impact on particle size and polydispersity, we found that increasing channel aspect ratio (H:W) and number of reacting interfaces significantly reduced particle size (p < 0.0001, p v 0.001, respectively). Careful tuning of microchannel geometry and flow parameters enabled preparation of NPs with diameter down to 65 nm.