Micromachines2015, 6(9), 1213-1235; doi:10.3390/mi6091213 - published 26 August 2015 Show/Hide Abstract
Abstract: In this work, we investigate the interaction of a nanoparticulate system for nanomedicine applications with the biological environment, i.e., the human body. Following the molecular communication paradigm, we assess how our nanoparticulate system model is suitable for coexistence in a biological environment. Specifically, we assume the presence of the human immune system that can affect the optimal behavior of nanoparticles, aiming to locally deliver drug inside the human body. When a flow of nanoparticles is injected into the blood, the interference due to the immune system can provide a strong decrease of the nanoparticle concentration, by means of “humoral immunity”, the phagocytosis process, etc. As a consequence, the correct drug delivery will occur with a lower probability. Since the mechanism behind the biological immune system is very complicated, in this paper, we start from a simplistic nanoparticulate model, where the nanoparticles and the cells of the immune system are subject to the diffusion laws. Finally, we derive the end-to-end physical model of our nanoparticulate nanomedicine system with the presence of the human immune system cells. The error analysis is then investigated in terms of how these errors can affect the performance of the system, i.e., nanoparticle survival probability.
Micromachines2015, 6(8), 1189-1212; doi:10.3390/mi6081189 - published 24 August 2015 Show/Hide Abstract
Abstract: Fish sense water motions with their lateral line. The lateral line is a sensory system that contains up to several thousand mechanoreceptors, called neuromasts. Neuromasts occur freestanding on the skin and in subepidermal canals. We developed arrays of flow sensors based on lateral line canal neuromasts using a biomimetic approach. Each flow sensor was equipped with a PDMS (polydimethylsiloxane) lamella integrated into a canal system by means of thick- and thin-film technology. Our artificial lateral line system can estimate bulk flow velocity from the spatio-temporal propagation of flow fluctuations. Based on the modular sensor design, we were able to detect flow rates in an industrial application of tap water flow metering. Our sensory system withstood water pressures of up to six bar. We used finite element modeling to study the fluid flow inside the canal system and how this flow depends on canal dimensions. In a second set of experiments, we separated the flow sensors from the main stream by means of a flexible membrane. Nevertheless, these biomimetic neuromasts were still able to sense flow fluctuations. Fluid separation is a prerequisite for flow measurements in medical and pharmaceutical applications.
Micromachines2015, 6(8), 1180-1188; doi:10.3390/mi6081180 - published 20 August 2015 Show/Hide Abstract
Abstract: The high throughput preparation of emulsions with high internal volume fractions is important for many different applications, e.g., drug delivery. However, most emulsification techniques reach only low internal volume fractions and need stable flow rates that are often difficult to control. Here, we present a centrifugal high throughput step emulsification disk for the fast and easy production of emulsions with high internal volume fractions above 95%. The disk produces droplets at generation rates of up to 3700 droplets/s and, for the first time, enables the generation of emulsions with internal volume fractions of >97%. The coefficient of variation between droplet sizes is very good (4%). We apply our system to show the in situ generation of gel emulsion. In the future, the recently introduced unit operation of centrifugal step emulsification may be used for the high throughput production of droplets as reaction compartments for clinical diagnostics or as starting material for micromaterial synthesis.
Micromachines2015, 6(8), 1166-1179; doi:10.3390/mi6081166 - published 18 August 2015 Show/Hide Abstract
Abstract: Two novel passive micromixers, denoted as the Y-Y mixer and the H-C mixer, based on split-and-recombine (SAR) principle are studied both experimentally and numerically over Reynolds numbers ranging from 1 to 100. An image analysis technique was used to evaluate mixture homogeneity at four target areas. Numerical simulations were found to be a useful support for the design phase, since a general idea of mixing of fluids can be inferred from the segregation or the distribution of path lines. Comparison with a well-known mixer, the Tear-drop one, was also performed. Over the examined range of Reynolds numbers 1 ≤ Re ≤ 100, the Y-Y and H-C mixers showed at their exit an almost flat mixing index characteristic, with a mixing efficiency higher than 90%; conversely the Tear-drop mixer showed a relevant decrease of efficiency at mid-range. Furthermore, the Y-Y and the H-C showed significantly less pressure drop than the Tear-drop mixer.
Micromachines2015, 6(8), 1157-1165; doi:10.3390/mi6081157 - published 17 August 2015 Show/Hide Abstract
Abstract: A dielectric liquid lens is prepared based on our previous work. By optimizing the device structure, the liquid lens presents a converging focus with good resolution and changes its focal length over a broad range with a low driving voltage. For a liquid lens with ~2.3 mm diameter in the relaxed state, it can resolve ~40 lp/mm. The resolution does not degrade during focus change. Its focal length can be varied from ~12 to ~5 mm when the applied voltage is changed from 0 to 28 Vrms. The response time of one cycle is ~2.5 s. Our liquid lens, with a low driving voltage for a large dynamic range, has potential applications in imaging, biometrics, optoelectronic, and lab-on-chip devices.
Micromachines2015, 6(8), 1143-1156; doi:10.3390/mi6081143 - published 14 August 2015 Show/Hide Abstract
Abstract: A biologically-inspired micropumping model in a three-dimensional tube subjected to localized wall constrictions is given in this article. The present study extends our previous pumping model where a 3D channel with a square cross-section is considered. The proposed pumping approach herein applies to tubular geometries and is given to mimic an insect respiration mode, where the tracheal tube rhythmic wall contractions are used/hypothesized to enhance the internal flow transport within the entire respiration network. The method of regularized Stokeslets-mesh-free computations is used to reconstruct the flow motions induced by the wall movements and to calculate the time-averaged net flow rate. The time-averaged net flow rates from both the tube and channel models are compared. Results have shown that an inelastic tube with at least two contractions forced to move with a specific time lag protocol can work as a micropump. The system is simple and expected to be useful in many biomedical applications.