Additively manufactured porous scaffolds by design for treatment of bone defects

There has been increasing attention to produce porous scaffolds that mimic human bone properties for enhancement of tissue ingrowth, regeneration, and integration. Additive manufacturing (AM) technologies, i.e., three dimensional (3D) printing, have played a substantial role in engineering porous scaffolds for clinical applications owing to their high level of design and fabrication flexibility. To this end, this review article attempts to provide a detailed overview on the main design considerations of porous scaffolds such as permeability, adhesion, vascularisation, and interfacial features and their interplay to affect bone regeneration and osseointegration. Physiology of bone regeneration was initially explained that was followed by analysing the impacts of porosity, pore size, permeability and surface chemistry of porous scaffolds on bone regeneration in defects. Importantly, major 3D printing methods employed for fabrication of porous bone substitutes were also discussed. Advancements of MA technologies have allowed for the production of bone scaffolds with complex geometries in polymers, composites and metals with well-tailored architectural, mechanical, and mass transport features. In this way, a particular attention was devoted to reviewing 3D printed scaffolds with triply periodic minimal surface (TPMS) geometries that mimic the hierarchical structure of human bones. In overall, this review enlighten a design pathway to produce patient-specific 3D-printed bone substitutions with high regeneration and osseointegration capacity for repairing large bone defects

Microfluidics for Advanced Drug Delivery Systems.

Considerable efforts have been devoted towards developing effective drug delivery methods. Microfluidic systems, with their capability for precise handling and transport of small liquid quantities, have emerged as a promising platform for designing advanced drug delivery systems. Thus, microfluidic systems have been increasingly used for fabrication of drug carriers or direct drug delivery to a targeted tissue. In this review, the recent advances in these areas are critically reviewed and the shortcomings and opportunities are discussed. In addition, we highlight the efforts towards developing smart drug delivery platforms with integrated sensing and drug delivery components

Recent microfluidic innovations for sperm sorting

Sperm selection is a clinical need for guided fertilization in men with low-quality semen. In this regard, microfluidics can provide an enabling platform for the precise manipulation and separation of high-quality sperm cells through applying various stimuli, including chemical agents, mechanical forces, and thermal gradients. In addition, microfluidic platforms can help to guide sperms and oocytes for controlled in vitro fertilization or sperm sorting using both passive and active methods. Herein, we present a detailed review of the use of various microfluidic methods for sorting and categorizing sperms for different applications. The advantages and disadvantages of each method are further discussed and future perspectives in the field are given

Microfluidic fuel cell for off-the-grid applications

The present doctoral thesis studies air-breathing microfluidic fuel cells with separated fuel and electrolyte streams as well as a membraneless fuel cell with selective electrodes. In order to gain more insight into the physio-chemical reactions, numerical simulation of the in-house developed air-breathing microfluidic fuel cell is formulated and solved using COMSOL Multiphysics. The results from the simulation show that fuel stream at the anode side and its interaction with the electrolyte stream has significant impact on the total fuel cell performance. As the first step for improving the hydrodynamic manipulation of the fuel stream, a flow-through porous anode is introduced. The effects of flow architecture on fuel utilization and the whole cell performance are investigated. Experimental results show that the flow-through porous anode improves the cell current in a long-term performance test as compared to the conventional design with flow-over planar anode. Because of the improved current generation, the rate of carbon dioxide generation in the cell increases. At high current densities, carbon dioxide produced in the channel emerges as bubbles that block and hinders reactant transport to the active sites of the anode.DOCTOR OF PHILOSOPHY (MAE

An air-breathing microfluidic formic acid fuel cell with a porous planar anode : experimental and numerical investigations

This paper reports the fabrication, characterization and numerical simulation of an air-breathing membraneless laminar flow-based fuel cell with carbon-fiber-based paper as an anode. The fuel cell uses 1 M formic acid as the fuel. Parameters from experimental results were used to establish a three-dimensional numerical model with COMSOL Multiphysics. The simulation predicts the mass transport and electrochemical reactions of the tested fuel cell using the same geometry and operating conditions. Simulation results predict that the oxygen concentration over an air-breathing cathode is almost constant for different flow rates of the fuel and electrolyte. In contrast, the growth of a depletion boundary layer of the fuel over the anode can be the major reason for low current density and low fuel utilization. At a low flow rate of 10 µl min−1, simulation results show a severe fuel diffusion to the cathode side, which is the main reason for the degradation of the open-circuit potential from 0.78 V at 500 µl min−1 to 0.58 V at 10 µl min−1 as observed in experiments. Decreasing the total flow rate 50 times from 500 µl min−1 to 10 µl min−1 only reduces the maximum power density approximately two times from 7.9 to 3.9 mW cm−2, while fuel utilization increases from 1.03% to 38.9% indicating a higher fuel utilization at low flow rates. Numerical simulation can be used for further optimization, to find a compromise between power density and fuel utilization.Accepted versio

Air-breathing microfluidic fuel cell with fuel reservoir

This paper describes the design and characterization of an air-breathing microfluidic fuel cell with a stationary fuel reservoir above the anode replacing the continuous fuel stream. Unlike other air-breathing microfluidic designs, the fuel is not in direct contact with electrolyte stream allowing the use of high fuel concentration. In addition, Ohmic losses are minimal because of the low anode-to-cathode spacing. Since the fuel passes through the catalyst layer of the anode, the conventional depletion boundary layer does not form. Improved mass transport compared to previous microfluidic designs is obtained because of a supply of a uniform fuel concentration over the anode and efficient bubble removal from the anode active sites. For practical applications, the fuel reservoir can be replaced by a pressurized fuel cartridge. The pressure is optimized according to the fuel concentration and the power density. This simple design of the fuel cell provides a low-cost but functional platform for practical applications

A review on membraneless laminar flow-based fuel cells

The review article provides a methodical approach for understanding membranelesslaminarflow-basedfuelcells (LFFCs), also known as microfluidic fuelcells. Membraneless LFFCs benefit from the lamination of multiple streams in a microchannel. The lack of convective mixing leads to a well-defined liquid–liquid interface. Usually, anode and cathode are positioned at both sides of the interface. The liquid–liquid interface is considered as a virtual membrane and ions can travel across the channel to reach the other side and complete the ionic conduction. The advantage of membraneless LFFC is the lack of a physical membrane and the related issues of membrane conditioning can be eliminated or becomes less important. Based on the electrode architectures, membraneless LFFCs in the literature can be categorized into three main types: flow-over design with planar electrodes, flow-through design with three-dimensional porous electrodes, and membraneless LFFCs with air-breathing cathode. Since this paper focuses on reviewing the design considerations of membraneless LFFCs, a concept map is provided for understanding the cross-related problems. The impacts of flow and electrode architecture on cell performance and fuel utilization are discussed. In addition, the main challenges and key issues for further development of membraneless LFFCs are discussed.Accepted versio

A membraneless hydrogen peroxide fuel cell using Prussian Blue as cathode material

This communication describes the exploitation of Prussian Blue, ferric ferrocyanide (Fe4III[FeII(CN)6]3), for the cathode side in a single-chamber membraneless fuel cell running on hydrogen peroxide (H2O2) as both fuel and oxidant. An open-circuit voltage (OCV) of 0.6 V has been obtained, which could be the highest OCV with H2O2 ever reported. The maximum power density was 1.55 mW cm−2 which showed a stable long-term operation in acidic media

Air-breathing membraneless laminar flow-based fuel cell with flow-through anode

This paper describes a detailed characterization of laminar flow-based fuel cell (LFFC) with air-breathing cathode for performance (fuel utilization and power density). The effect of flow-over and flow-through anode architectures, as well as operating conditions such as different fuel flow rates and concentrations on the performance of LFFCs was investigated. Formic acid with concentrations of 0.5 M and 1 M in a 0.5 M sulfuric acid solution as supporting electrolyte were exploited with varying flow rates of 20, 50, 100 and 200 μl/min. Because of the improved mass transport to catalytic active sites, the flow-through anode showed improved maximum power density and fuel utilization per single pass compared to flow-over planar anode. Running on 200 μl/min of 1 M formic acid, maximum power densities of 26.5 mW/cm2 and 19.4 mW/cm2 were obtained for the cells with flow-through and flow-over anodes, respectively. In addition, chronoamperometry experiment at flow rate of 100 μl/min with fuel concentrations of 0.5 M and 1 M revealed average current densities of 34.2 mA/cm2 and 52.3 mA/cm2 with average fuel utilization of 16.3% and 21.4% respectively for flow-through design. The flow-over design had the corresponding values of 25.1 mA/cm2 and 35.5 mA/cm2 with fuel utilization of 11.1% and 15.7% for the same fuel concentrations and flow rate.Accepted versio

Microfluidics for Advanced Drug Delivery Systems.

Considerable efforts have been devoted towards developing effective drug delivery methods. Microfluidic systems, with their capability for precise handling and transport of small liquid quantities, have emerged as a promising platform for designing advanced drug delivery systems. Thus, microfluidic systems have been increasingly used for fabrication of drug carriers or direct drug delivery to a targeted tissue. In this review, the recent advances in these areas are critically reviewed and the shortcomings and opportunities are discussed. In addition, we highlight the efforts towards developing smart drug delivery platforms with integrated sensing and drug delivery components