Abstract: This paper describes multi-scale interface for bio and medical engineering based on MEMS technology. MEMS technology can provide various interfaces for biomedical application corresponding to hierarchical components of living organism such as cell, tissue, and organ. This paper mainly deals with small, soft, and safe (S3) micromachine as multi-scale interfaces for medical application. Micromachine is small in nature. S3 micromachine is based on its soft and flexible structure and safe driving principle. These features are suitable for advanced medical tools for minimally invasive medical operations. S3 micromachines-based medical tool has been applied to a retractor for spacing in front of the endoscope at our early stage. This paper also presents the S3 micromachine as a surgical tool for a cell sheet transplantation in an eye.
Abstract: UV micro-casting is a promising mass production method for replication of polymeric microdevices due to the non-stringent process conditions and fast curing time. This paper describes a potential method to mass produce polymeric microdevices. The first generation mold for UV micro-casting was fabricated by using chemically micro-etched copper clad laminate (CCL) base substrate. Subsequently a two part silicone rubber was cast over the CCL micro-feature mold. Photosensitive resin was dispensed onto the silicone rubber mold and a transparent Mylar thin film was placed on top of the UV curable prepolymer. After the silicone rubber mold-resin-Mylar assembly was UV irradiated for tens of seconds, the crosslinked polymer, together with the Mylar film was peeled off from the mold. The cross-linked polymer was placed on top of a second layer of Mylar film dispensed with the similar UV curable resin. In this way, a complete polymeric micro device could be efficiently produced.
Abstract: This paper presents a number of plasmonics based nanosensors that is currently being investigated in IHPC. In the first case, the influence of external magnetic field and electron on the field distribution of active semiconductor microcavity with elliptical shape is studied. It is observed that high amount of electron pumped into the elliptical microcavity demonstrate the plasmonics field distribution, which can be used to sense the change in wavelength and electron/holes densities. The second case will discuss about using plasmonics to enhance the electromagnetic wave from metallic waveguide slot. The enhancement is more than 100 times and this is important for the generation of electron-holes pair in PIN based photo-detector. The third case will discuss using the metallic nanowire to sense different surrounding materials. The small differences in the refractive index of the surrounding materials show the different plasmonics resonance frequencies.
Abstract: In this paper, light-driven acoustic band gap is presented by considering two metal nanospheres illuminated simultaneously by laser and acoustic waves. The interaction between the photonics and phonons is investigated through optical distribution force, van der Waals distribution force, and acoustic pressure upon these nanospheres. Based on the optical force and van der Waals force, the acoustic form functions for the metal nanoaggregates with different optical intensity are calculated, and the light-driven acoustics band gap at low frequency band has been found. It is shown that the band gap width can be widened with increasing the incident laser intensity, or by using proper metal materials and background media. This could provide potential applications in optical nanoswitches and acoustical filters.
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: 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: Several devices of microelectromechanical systems (MEMS) are analyzed in the presented work, using a novel numerical meshless method called the random differential quadrature (RDQ) method. The differential quadrature (DQ) is an effective derivative discretization technique but it requires all the field nodes to be arranged in a collinear manner with a pre-defined pattern. This limitation of the DQ method is overcome in the RDQ method using the interpolation function by the fixed reproducing kernel particle method (fixed RKPM). The RDQ method extends the applicability of the DQ method over a regular as well as an irregular domain discretized by uniform or randomly distributed field nodes. Due to the strong-form nature, RDQ method captures well the local high gradients. These features of the RDQ method enable it to efficiently solve the MEMS problems with different boundary conditions. In the presented work, several MEMS devices that are governed by the nonlinear electrostatic force are analyzed using the RDQ method, and their results are compared with the other simulation results presented in the existing literature. It is seen that the RDQ method effectively and accurately solves the MEMS devices problems.
Abstract: A mathematical model of a microfluidic controller comprising a hydrogel in a typical T- and Y-junction is derived and presented. The model takes into account conservation of momentum, mass and ions for laminar incompressible flow and the deformation/sensing of a pH-sensitive hydrogel. The response of the pH-responsive hydrogel is validated with experimental equilibrium swelling curves for which good agreement is found. The model is employed to study the behavior of the hydrogel and its impact on the overall fluid flow in different microfluidic flow channel/hydrogel configurations, e.g. in a T-junction, where the hydrogel can act autonomously and without external power supply to regulate the flow. Finally, we discuss how the model can be generalized for other types of stimuli-responsive hydrogels.
Abstract: In this paper, we report our recent studies on developing nonlinear techniques based on a single SOA for all-optical signal processing at high-speed, with a focus on simple configurations employing commercial SOAs for several key all-optical network applications. Our researches are based on nonlinear polarization rotation (NPR), four-wave mixing (FWM) and cross-phase modulation (XPM) effects in a single SOA. We propose and demonstrate applications of the nonlinear techniques in all-optical logic gates, multi-function format coversion, tunable Lyot birefringent filter and multi-channel optical time division multiplexed (OTDM) demultiplexing.