Recapitulating the Vasculature using organ-on-chip technology

\u3cp\u3eThe development of Vasculature-on-Chip has progressed rapidly over the last decade and recently, a wealth of fabrication possibilities has emerged that can be used for engineering vessels on a chip. All these fabrication methods have their own advantages and disadvantages but, more importantly, the capability of recapitulating the in vivo vasculature differs greatly between them. The first part of this review discusses the biological background of the in vivo vasculature and all the associated processes. We then evaluate the biological relevance of different fabrication methods proposed for Vasculature-on-Chip, we indicate their possibilities and limitations, and we assess which fabrication methods are capable of recapitulating the intrinsic complexity of the vasculature. This review illustrates the complexity involved in developing in vitro vasculature and provides an overview of fabrication methods for Vasculature-on-Chip in relation to the biological relevance of such methods.\u3c/p\u3

Reynolds number effects in a turbulent pipe flow for low to moderate Re

We present in this paper high resolution, two-dimensional LDV measurements in a turbulent pipe flow of water over the Reynolds number range 500025000. Results for the turbulence statistics up to the fourth moment are presented, as well as power spectra in the near-wall region. These results clearly show that the turbulence statistics scaled on inner variables are Reynolds-number dependent in the aforementioned range of Reynolds numbers. For example, the constants in the dimensionless logarithmic mean-velocity profile are shown to vary with Reynolds number. Our conclusion that turbulence statistics depend on the Reynolds number is consistent with results found in other flow configurations, e.g., a channel flow. Our results for the pipe flow, however, lead nevertheless to quite different tendencies

Workshop meeting report Organs-on-Chips : human disease models

The concept of Organs-on-Chips has recently evolved and has been described as 3D (mini-) organs or tissues consisting of multiple and different cell types interacting with each other under closely controlled conditions, grown in a microfluidic chip, and mimicking the complex structures and cellular interactions in and between different cell types and organs in vivo, enabling the real time monitoring of cellular processes. In combination with the emerging iPSC (induced pluripotent stem cell) field this development offers unprecedented opportunities to develop human in vitro models for healthy and diseased organ tissues, enabling the investigation of fundamental mechanisms in disease development, drug toxicity screening, drug target discovery and drug development, and the replacement of animal testing. Capturing the genetic background of the iPSC donor in the organ or disease model carries the promise to move towards in vitro clinical trials , reducing costs for drug development and furthering the concept of personalized medicine and companion diagnostics. During the Lorentz workshop (Leiden, September 2012) an international multidisciplinary group of experts discussed the current state of the art, available and emerging technologies, applications and how to proceed in the field. Organ-on-a-chip platform technologies are expected to revolutionize cell biology in general and drug development in particular

Micro-moulded magnetic artificial cilia for anti-fouling surfaces

Cilia are microscopic hair-like filaments found in nature which can perform such functionalities as swimming, feeding, and particle manipulation [1]. The particle manipulation property of cilia has been extensively studied by the group of prof. Anna Balazs and co-workers using computational modelling [2]. Inspired by these, we propose the use of artificial cilia to create anti-fouling surfaces in man-made applications.\u3cbr/\u3eWe have fabricated magnetically actuated artificial cilia using an out-of-cleanroom, cost-effective and time-saving method – micro-moulding technology. The moulding process consists of seven steps: (1) moulds featured micro-holes are fabricated using photo-lithography; (2) a mixture composed of a base PDMS + curing agent and iron particles (P-I) is poured onto the mould, followed by a degassing procedure; (3) the top part of P-I which is outside of the micro-holes, is removed; (4) the mould is placed in a uniform magnetic field to align the iron particles; (5) pure base PDMS + curing agent are poured onto the mould, which will form the so-called base for cilia; (6) the liquid-like composition which covers the mould is cured in an oven; (7) the cured P-I – PDMS is peeled off the mould. Finally, we obtain magnetic artificial cilia, which “stand” on a transparent PDMS base (Fig. 2).\u3cbr/\u3eMagnetic artificial cilia made with the micro-moulding method can perform a tilted conical movement mimicking the motion of cilia in nature, which is achieved by positioning a rotating magnet underneath the PDMS base. An actuation video can be found on https://www.youtube.com/watch?v=9KVCVMa3Lvk . Our next step is to characterize the particle manipulation capability of our cilia and then to create an anti-fouling surface

Sorting algal cells by morphology in spiral micro channels using inertial microfluidics

Sub-millimetre phytoplankton (here referred to as algae) exist in a wide variety of shapes and sizes. Measuring algae morphology can be a useful tool for understanding the species dynamics in a body of water, and size-sorting in general is a valuable first step in automated species identification. Here, we demonstrate the sorting of algae by shape and size in a spiral microchannel, in which lift forces and Dean flow drag forces combine to position the cells in a shape-dependent location in the channel cross section. Three species were used for experiments: the high-aspect-ratio cylindrical Monoraphidium griffithii, the prolate spheroidal Cyanothece aeruginosa, and the small spherical Chlorella vulgaris. These results are compared with the sorting of similarly sized polystyrene latex microspheres in the same device over the same range of flow rates. Tests were done at conditions which yielded average Dean numbers over the channel length of 3 < De < 30. At 1.6 mL/min, the 10- and 20-μm microspheres could be separated with an efficiency of 96 %. The best sorting results for the algae were obtained at a flow rate of 3.2 mL/ min, which yielded an average Dean number of De = 25 over the channel length. These conditions led to the separation of the Monoraphidium from the differently shaped Cyanothece; these two species could be sorted with a 77 % separation efficiency despite the relatively high polydispersity in cell sizes within each species. The elegance and simplicity of inertial microfluidics make it appropriate for the high-throughput pre-sorting of algae cells upstream of other integrated sensing modalities in a field-deployable device

Residual stresses in multilayer ceramic capacitors: measurement and computation

In this paper, we present a combined experimental and computational study of the thermomechanical reliability of multilayer ceramic capacitors (MLCC's). We focus on residual stresses introduced into the components during the cooling down step of the sintering process. The technique of microindentation turned out to be a useful method to measure the stresses locally. The computations were done with three-dimensional finite element simulations. We find that the cooling step introduces compressive in-plane stresses in the ceramic layers. There is reasonably good overall agreement between the residual stresses obtained from the indentation experiments and the numerical simulations. Some discrepancies do exist, though, for measurements on cross-sectioned MLCC's. Possible reasons for the differences are discussed

A novel breast cancer model of early stage invasion:using microfluidic methods to mimic a heterogeneous physical tumor microenvironment

The majority of breast cancer deaths are not caused by the primary tumor, but by metastasis to other organs. In this work, we propose a novel in vitro breast cancer model that focuses on dissecting the influence of the biophysical properties of the extracellular matrix (ECM) on the onset of cancer invasion. Based on microfluidic technology, it will provide us with the necessary tools to independently vary different material and cell properties, while it provides the cells with a physiologically relevant environment.\u3cbr/\u3