Nanoscale membrane actuator for in vitro mechano-stimuli responsive studies of neuronal cell networks on chip

\u3cp\u3eIn order to investigate the hypothesis that dynamic nanoscale stimuli can influence the functional response of the brain, in this paper we describe the development of a membrane actuator chip based on polydimethylsiloxane (PDMS) soft lithography. The chip exerts a local nanoscale mechanical load on an in vitro neuronal cell network by microfluidic pneumatic deformation of the membrane. The deformation provides a topographical change in the substrate as an input stimulus for the study of response functions of a neuronal cell network in vitro. Calcium ions (Ca\u3csup\u3e2+\u3c/sup\u3e) imaging within a neuronal cell network grown from dissociated cortical cells of the rat's brain used as a brain model indicates that a neural networks response can be provoked by means of our new method. This actuator chip provides a relatively mild and localised mechanical stimulus by means of a 2% elongation of the membrane's width during the application of a pressure pulse underneath the membrane using a microfluidic channel design. We found an average 50% increase of the intracellular Ca\u3csup\u3e2+\u3c/sup\u3e flux activity for 2D neuronal cell networks among 4 independent samples cultured on flat membranes. Additionally, we have proven the applicability of the actuator chip for networks on nanogrooved membranes by the observation of Ca\u3csup\u3e2+\u3c/sup\u3e traces and we also observed the Ca\u3csup\u3e2+\u3c/sup\u3e waves response upon stimulation in a three dimensional (3D) in vivo-like neuronal cell network using Matrigel on flat membranes. Hence, the chip potentially provides a novel technology platform for the in vitro modelling of brain tissues with topographically and 3D hydrogel-defined network architectures.\u3c/p\u3

Influence of the water phase state on the thermodynamics of aqueous phase reforming for hydrogen production

\u3cp\u3eHydrogen is a promising renewable energy source that can be produced from biomass using aqueous-phase reforming (APR). Here, using data obtained from AspenPlus and the literature, we evaluated the phase state, temperature-dependent enthalpy, and Gibbs free energy for the APR of small biomass model substrates. Phase equilibrium studies reveal that, under typical APR reaction conditions, the reaction mixture is in the liquid phase. Therefore, we show for the first time that the water-gas shift reaction (WGSR), which is the second main reaction of APR, must be modeled in the liquid phase, resulting in an endothermic instead of an exothermic enthalpy of reaction. A significant implication of this finding is that, although APR has been introduced as more energy saving than conventional reforming methods, the WGSR in APR has a comparable energy demand to the WGSR in steam reforming (SR).\u3c/p\u3

Fabrication and characterization of microsieve electrode array (μSEA) enabling cell positioning on 3D electrodes

\u3cp\u3eHere the fabrication and characterization of a novel microelectrode array for electrophysiology applications is described, termed a micro sieve electrode array (μSEA). This silicon based μSEA device allows for hydrodynamic parallel positioning of single cells on 3D electrodes realized on the walls of inverted pyramidal shaped pores. To realize the μSEA, a previously realized silicon sieving structure is provided with a patterned boron doped poly-silicon, connecting the contact electrodes with the 3D sensing electrodes in the pores. A LPCVD silicon-rich silicon nitride layer was used as insulation. The selective opening of this insulation layer at the ends of the wiring lines allows to generate well-defined contact and sensing electrodes according to the layout used in commercial microelectrode array readers. The main challenge lays in the simultaneously selective etching of material at both the planar surface (contact electrode) as well as in the sieving structure containing the (3D) pores (sensing electrodes). For the generation of 3D electrodes in the pores a self-aligning technique was developed using the pore geometry to our advantage. This technique, based on sacrificial layer etching, allows for the fine tuning of the sensing electrode surface area and thus supports the positioning and coupling of single cells on the electrode surface in relation to the cell size. Furthermore, a self-aligning silicide is formed on the sensing electrodes to favour the electrical properties. Experiments were performed to demonstrate the working principle of the μSEA using different types of neuronal cells. Capture efficiency in the pores was >70% with a 70% survival rate of the cell maintained for up to 14 DIV. The TiSi\u3csub\u3e2\u3c/sub\u3e-boron-doped-poly-silicon sensing electrodes of the μSEA were characterized, which indicated noise levels of \u3c/p\u3

High pressure check valve for application in a miniature cryogenic sorption cooler

This paper presents a check valve with integrated filter that can stand gas pressures of more than 100 bar in the closed direction and which has a very low pressure drop at low abs. gas pressures in the forward direction. The check valve is designed as a part of a check valve unit for application in a miniature cooler for cryogenic temps. (<120 K). This cooling system, which utilizes several micromachined components, will in this paper be introduced to the MEMS field. [on SciFinder (R)

The influence of nanoscale grooved substrates on osteoblast behavior and extracellular matrix deposition

To fight bone diseases characterized by poor bone quality like osteoporosis and osteoarthritis, as well as in reconstructive surgery, there is a need for a new generation of implantable biomaterials. It is envisioned that implant surfaces can be improved by mimicking the natural extracellular matrix of bone tissue, which is highly a organized nano-composite. In this study we aimed to get a better understanding of osteoblast response to nanometric grooved substrates varying in height, width and spacing. A throughput screening biochip was created using electron beam lithography. Subsequently, uniform large-scale nanogrooved substrates were created using laser interference lithography and reactive ion etching. Results showed that osteoblasts were responsive to nanopatterns down to 75 nm in width and 33 nm in depth. SEM and TEM studies showed that an osteoblast-driven calcium phosphate (CaP) mineralization was observed to follow the surface pattern dimensions. Strikingly, aligned mineralization was found on even smaller nanopatterns of 50 nm in width and 17 nm in depth. A single cell based approach for real time PCR demonstrated that osteoblast-specific gene expression was increased on nanopatterns relative to a smooth control. The results indicate that nanogrooves can be a very promising tool to direct the bone response at the interface between an implant and the bone tissue

Micro and nanotechnology for biological and biomedical applications

10.1007/s11517-010-0677-zMedical and Biological Engineering and Computing4810941-943MBEC

Simulation-based analysis of flow due to traveling- plane-wave deformations on elastic thinfilm actuators in micropumps

One of the propulsion mechanisms of microorganisms is based on propagation of bending deformations on an elastic tail. In principle, an elastic thin-film can be placed in a channel and actuated for pumping of fluids by means of introducing a series of traveling-wave deformations on the film. Here, we present a simulationbased analysis of transient two-dimensional Stokes flow induced by propagation of sinusoidal deformations on an elastic thin-film submerged in a fluid between parallel plates. Simulations are based on a numerical model that solves timedependent Stokes equations on deforming mesh, which is due to the motion of the thin-film boundary and solved with the arbitrary Lagrangian Eulerian (ALE) method. Effects of the wavelength, frequency, amplitude and channel's height on the time-averaged flow rate and the rate-of-work done on the fluid by the thinfilm are demonstrated and grouped together as the flow-rate and power parameters to manifest a combined parametric dependence