Micro and Nanosystems - Volume 1, Issue 3, 2009

The development of the molecular imprinting concept over the past five years is reviewed with particular emphasis on an understanding of the underlying principles and applications to medicine, the environment and security. All aspects of imprinted polymers are surveyed, especially methods for production and characterization.

Microfluidic continuous cell separation based on hydrodynamic interaction in a microfluidic channel has attracted attention because of its robustness, high throughput and cell viability. This paper systematically gives an overview on recent advances in hydrodynamic particle and cell separation in microfluidic devices. It presents the basic ideas and fluid mechanics for the hydrodynamic interaction of a particle in a microfluidic system. Secondly, different kinds of devices are introduced with detailed descriptions of their mechanisms, designs and performances. Finally, the review addresses some practical issues of microfluidic sorting devices for use in biological or medical studies.

Polymer synthesis requires strict control of reaction conditions such as temperature, reaction time, and mixing of reagents. Microfluidic reaction systems enable efficient mixing and rapid heat exchange. Moreover, laminar stream in a microfluidic channel enables control of the resulting shape of a molecule. This article reviews the use of microfluidic technology in the field of polymer chemistry. First, conformational aspects of polymers in microfluid are summarized. Next, the techniques for linear and branched polymer synthesis are described. We also describe the potential use of microreaction system for polymer particle and membrane synthesis. A description of how it would be possible to use this technology to prepare larger quantities of polymer compounds is also given.

The wear characteristics of WC/Co micropunch (150 µm in diameter) in various processing periods were investigated. After the punching microhole test with Ti as substrate, the effect of punching numbers on the wear loss and surface morphology had been studied by confocal laser, scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX) etc. Results showed that in the initial micropunch processing, the wear of micropunch was significantly increased, and the dominant factors of the wear loss mainly relied on Co. With the increment of punching numbers, the wear of WC/Co micropunch was in the quasistable period with a little wear loss. When the punching number exceeded 1525, the wear of micropunch was increased distinctly with the wear loss of Co and WC both. Moreover, with the punching numbers increasing further, the dominant factors of the wear loss mainly relied on WC. Meanwhile, attributed to the wear of micropunch, the quality of microholes was decreased correspondingly.

Faster machining time is the main factor in improving the machining efficiency in µ-EDM processes. This paper presents the effect of micro MoS2 powder mixed dielectric fluid on reducing machining time. It was found that suspension of micro MoS2 powder in dielectric fluid significantly reduces machining time up to 50 % compared to machining time in pure dielectric fluid.

We present in this paper a complete study of PZT thin films grown by r.f. sputtering onto platinised silicon substrates; the films are deposited at room temperature and post annealing is necessary to crystallise the PZT in the perovskite phase. The PZT composition (ratio Zr/Ti) is fixed to 54/46, i.e. in the morphotropic region where the piezoelectric activity is a maximum. For a future use in MEMS/NEMS it is imperative to know the intrinsic piezoelectric coefficients of the films; in particular the coefficients are d33, e31 and d31 are the most important to obtain. To determine these we have developed an experimental set-up based upon a commercial laser Doppler vibrometer and specific sample preparation procedures developed in the laboratory. These are necessary so that we do not integrate the substrate contribution with the measurement of the piezoelectric coefficient. The macro-structure of the PZT films is treated in this paper, as well as the micro and nano structure of the thin films and devices. This work has focused on two main objectives: optimisation of the etched processes: IBE (RIE) for micro structure fabrication and FIB for nanostructure and evaluation of the electrical degradations induces by the etching processes. We have optimised the process in order that functional performance is not degraded after etching.

The investigation of fluid flow in a tube or channel commenced from studying experimentally the liquid flow along a circular tube under the pressure difference imposed at both the ends, the results were verified by the exact solution of the Navier-Stokes Eq. under constant pressure gradient assumption (Poiseuille flow). The experimental work has been playing a pioneering role in the investigation of channel flows. In the case of gas for the tube (or channel) flow, according to the global mass conservation law, the pressure gradient is never a constant. The theoretical studies on rarefied gas Poiseuille flow based on constant pressure gradient assumption still compared well with the early experimental work because when pressure difference between the inlet and the outlet is small in comparison with the average pressure, the pressure distribution is approximately a linear one. Recently non-linear pressure distribution was experimentally found in the integrated micro- channel/pressure sensor systems with gas flow in the transitional regime. The mass flow rate of micro channel was exactly measured, challenging the rarefied gas dynamics community to put forward computation or simulation means for the calculation of micro-channel flow, and the flow characteristics in other micro devices. This paper reviews some of these computational efforts. It also presents a strict kinetic solution of the finite length micro-channel flow problem based on the global mass conservation and the exact kinetic theoretical solution of the Poiseuille flow at each section. Calculations and simulations are compared with reviewed experiments to check the agreement between the computational or theoretical results with experimental data.

In the present article the modeling approach and the control design aspects of an electrostatic microactuator (EmA) under the effect of squeezed film damping are presented. The model of the system accounts for an EmA composed by a set of two plates. The bottom plate is clamped to the ground, while the moving plate is driven by an electrically induced force which is opposed by the force exerted by a spring element. The nonlinear model of the EmA is linearized at various operating points, and the feedforward compensator provides the nominal voltage. Subsequently a gain scheduled H∞ controller is used to tune the controller-parameters depending on the EmA's operating conditions. The controller is designed at various operating points based on the distance between the two plates. The controller's parameters are tuned in an optimal manner and are computed via the use of the Linear Matrix Inequalities. Special attention has been paid in order to examine the properties of the EmA regarding the bifurcations points. Finally, numerous simulation cases are presented in order to prove the efficacy of the presented controller.