Papers by Keyword: Bio-MEMS

Abstract: This research developed a micro-silicon cell filter using MEMS fabricating technology, which has constant filtering channel size, uniformed distribution, and good surface quality. Blood cell filtering experiment was carried out by applying pressure injection and the filtering quality was studied via cell counting. The experimental results demonstrates that flat plate filter can implement blood cells filtering separation, and erythrocyte recycling rate reaches 90% with the 4～5m in filtering size and 0.1L/min injection flow-rate fulfilling the requirement of blood cells separation. Increasing the flow-rate can improve filtering efficiency to a certain degree but has little effect on erythrocyte recycling rate, because micro array filter is insensitive to back pressure in contract to the filled filter.

Abstract: Proton beam writing (PBW) is a MeV ion beam lithography technique that has gained interest in many biological applications such as fabricating microfluidic devices for Lab-On-a-Chip (LOC) applications where capillary forces are important for fluid flow. PBW has a unique capability of being able to direct-write patterns in thick (1-30µm) polymer resist layers with straight vertical sidewalls. It can be used to prepare master stamps and moulds for mass production in polymeric materials. A recent development, where the direct writing of an entire pattern element is carried out in parallel makes PBW especially well suited for Bio-MEMS LOC applications. In this study we have examined the flow dynamics using video microscopy of deionised water in fluidic channel patterns fluid reservoirs, capillary sections and a capillary pump written by PBW. The video microscopy data also demonstrated that the wetting behavior of the surface strongly influences the dynamics of fluid flow. This makes new approaches for LOC fabrication feasible and powerful.

Abstract: Based on Donnan’s equilibrium, a simple chemo-mechanical model is developed to study the transient swelling behavior of the pH-sensitive hydrogel for design and optimization of smart hydrogel-based BioMEMS device. The model is mathematically composed of several governing equations, including Fick’s law which describes the diffusion process in the buffer solution, the fixed charge density formula associated with pH value of the buffer solution, and mechanical equation which gives the swelling ratio responding to pH. The model also considers several chemical conditions, including Donnan’s equilibrium condition which gives Donnan partitioning ratio relating to the concentrations of ionic species in the interior hydrogel and the external solution, the electroneutrality condition in the interior hydrogel and bathing solution as well. The model is capable of predicting the kinetics process of the smart hydrogel immersed in buffer solution with change in pH. The simulation of the diffusion-swelling behavior of the pH-sensitive hydrogel is presented, and the responsive deformation of the smart hydrogel to the solution pH is discussed in detail.

Abstract: A continuum multiphysics theory is presented for simulation of the ionic-strength-sensitive hydrogel and surrounding solution. The theory considers the coupled effects of chemical, electrical and mechanical multi-energy domains on the swelling behavior of the ionic-strength-sensitive hydrogel and is thus termed the multi-effect-coupling ionic-strength-stimuli (MECis) model. The MECis model consists of several governing equations, including Nernst-Planck flux system, Poisson equation, fixed charge density and mechanical equilibrium equation, in which the effect of the ionic strength is incorporated into the governing equation of diffusive flux and fixed charge. The theory is capable of simulating the swelling/shrinking behavior of smart hydrogel in buffer solution subject to the change in the ionic strength, and providing the distribution of the ionic concentration and electrical potential for applications of BioMEMS design. Apart from the ionic strength as the main stimulus, the influence of several parameters is discussed in detail, including the initial fixed charge density and Young’s modulus of the hydrogel.

Abstract: Parylene C, an emerging material in microelectromechanical systems (MEMS), is now widely applied to neural prosthesis devices, such as artificial retinal implants, due to its well-known biocompatibility and ability to be easily patterned by oxygen plasma etching. This work presents a flexible parylene-based microelectrode array（MEA）using MEMS techniques aiming for the chronic subretinal stimulation. The MEA was successfully manufactured and inserted into the subretinal space of a rabbit eye by a novel surgical operation. Optical Coherence Tomography(OCT) showed that a chronic implantation of parylene-based electrode arrays in the rabbit retina over a three month follow-up period demonstrated that the present chip system has a good biocompatibility with the subretinal organs without obvious damages.

Abstract: We investigated the plasma etching of polysiloxane intended for use in cochlear implants as a protection layer. The processing was performed using fluorine-based chemistry ionized in RIE (Reactive Ion Etching) or ICP (Inductively Coupled Plasma) discharge. The effect of temperature on polysiloxane etch rate and the resulting surface morphology was examined. XPS was employed to determine chemical changes induced by plasma treatment. The cytotoxicity on a cell line was observed in order to estimate suitability of plasma processed silicone elastomer for use in biomedical applications. This paper presents the selected results, which reveals how the polysiloxane surface properties can change depending upon plasma treatment conditions. Exemplary micro devices encapsulated in plasma treated silicone elastomer are also shown.

Abstract: Ammonia implanted silicon was performed by using plasma immersion ion implantation (PIII) to form a silicon nitride films. Blood compatibility of the prepared samples was investigated by platelets adhesion testing. It showed less activation i.e. lower thrombosis risks occurs on the prepared silicon nitride films than control silicon sample. The enhanced blood compatibility of the material is attributed to the modified surface properties such as hydrophilicity from thermodynamic adsorption perspective, which is related to surface chemical bonding states achieved by PIII process.

Abstract: Amplification of the p53 gene using the polymerase chain reaction (PCR) was performed in a silicon-based micro-PCR chip. Metal deposition, photolithography, and anodic bonding were used to fabricate micro-PCR chip and a thermal cycling system with dual peltier devices and PID controller was integrated for controlling the cycling temperature of the PCR mixture. We have demonstrated the amplification of exon 6(182bp) of the p53 gene with the micro-fabricated PCR chip. Temperature control accuracy was within
0.5  . The amplified p53 genes using both conventional PCR and micro fabricated PCR were analyzed using micro-capillary electrophoresis. The PCR performance strongly depends on the cycling temperature, and the Si surface treatment with protein. The micro-PCR products show higher specificity than those of conventional PCR products, and this is attributed to the uniform temperature distribution of the PCR mixture in micro-chip.