EFAB: Batch Production of Functional, Fully-Dense Metal Parts with Micron-Scale Features

EFAB (Electrochemical FABrication) is a new SFF process with the potential to economically fabricate prototypes or mass production quantities of functional, mesoscale-microscale parts and mechanisms. EFAB generates an entire layer simultaneously-versus serially, as with most SFF. Based on electrodeposition, EFAB allows ultra-thin layers (2-10 microns, or even submicron) that minimize stairsteps, and generates a net-shape, fully-dense metal structure that can be homogeneous and isotropic. Minimum feature width is approximately 25 microns, and can be reduced further. EFAB can be used to manufacture micromachines and microelectromechanical systems (MEMS), offering significant advantages over current processes: e.g., true 3-D geometry, IC compatibility, low capital investment, and process automation.Mechanical Engineerin

Size Effect on Micro-Droplet Movement due to Marangoni Effect

ABSTRACT Fundamental physics are studied on the movement of droplets for sizes ranging from 0.1 µl to 1.0 µl on a solid surface subjected to temperature gradients using numerical computations and the comparison with experiments. The receding/advancing contact angles relating to the droplet size and shape are the key parameters of droplet moving and the differences subjected to the temperature gradients induce unbalanced recirculation zones inside the moving droplet, thus induces driving force to drag the droplet. It is found that droplet of smaller size moves faster with smoothly changing speed and the droplet of larger size moves with fluctuating speed and the average moving speed is roughly the same magnitude as that with two-dimensional heating. INTRODUCTION As the liquid droplet in microscale size, surface tension is the major driving force to pump the droplet in motion without any moving parts in a device. For example, Burns et a

A Simple Fiber Bragg Grating-Based Sensor Network Architecture with Self-Protecting and Monitoring Functions

A novel fiber Bragg grating (FBG)-based passive sensor architecture, which can be used to protect the fiber cut and monitor the multiple sensors simultaneously, is proposed and experimentally demonstrated. Here, we employ a wavelength-tunable erbium-doped fiber (EDF) laser scheme with 25 km cavity length acting as the detecting light source in central office (CO). Each FBG sensor, serving as a feedback element, is used in proposed sensor architecture. By tuning the tunable bandpass filter (TBF) placing inside cavity to match the corresponding Bragg wavelength of FBG over the amplification bandwidth, we can retrieve the related wavelength lasing for the FBG sensing and monitoring simultaneously. Moreover, the survivability and capacity of the passive FBG sensor architecture can be also enhanced

Gradient static-strain stimulation in a microfluidic chip for 3D cellular alignment

This is the published version. Copyright 2014 Royal Society of ChemistryCell alignment is a critical factor to govern cellular behavior and function for various tissue engineering applications ranging from cardiac to neural regeneration. In addition to physical geometry, strain is a crucial parameter to manipulate cellular alignment for functional tissue formation. In this paper, we introduce a simple approach to generate a range of gradient static strains without external mechanical control for the stimulation of cellular behavior within 3D biomimetic hydrogel microenvironments. A glass-supported microfluidic chip with a convex flexible polydimethylsiloxane (PDMS) membrane on the top was employed for loading the cells suspended in a prepolymer solution. Following UV crosslinking through a photomask with a concentric circular pattern, the cell-laden hydrogels were formed in a height gradient from the center (maximum) to the boundary (minimum). When the convex PDMS membrane retracted back to a flat surface, it applied compressive gradient forces on the cell-laden hydrogels. The concentric circular hydrogel patterns confined the direction of hydrogel elongation, and the compressive strain on the hydrogel therefore resulted in elongation stretch in the radial direction to guide cell alignment. NIH3T3 cells were cultured in the chip for 3 days with compressive strains that varied from ~65% (center) to ~15% (boundary) on hydrogels. We found that the hydrogel geometry dominated the cell alignment near the outside boundary, where cells aligned along the circular direction, and the compressive strain dominated the cell alignment near the center, where cells aligned radially. This study developed a new and simple approach to facilitate cellular alignment based on hydrogel geometry and strain stimulation for tissue engineering applications. This platform offers unique advantages and is significantly different from the existing approaches owing to the fact that gradient generation was accomplished in a miniature device without using an external mechanical source

Measurement of Organic Chemical Refractive Indexes Using an Optical Time-Domain Reflectometer

In this investigation, we propose and experimentally demonstrate a method for measuring the refractive index (RI) of liquid organic chemicals. The scheme is based on a single-mode fiber (SMF) sensor and an optical time-domain reflectometer (OTDR). Here, due to the different reflectance (R) between the SMF and organic liquid chemicals, the reflected power level of the backscattering light (BSL) measured by the OTDR would be different. Therefore, we can measure the RI of chemical under test via the measured BSL level. The proposed RI sensor is simple and easy to manipulate, with stable detected signals, and has the potential to be a valuable tool for use in biological and chemical applications

Droplet microreactor for reaction monitoring at elevated temperatures and pressure

Recording reaction kinetics in detail and at various reaction conditions can be a time-consuming process. Microdroplets form ideal reaction chambers, suitable for high-throughput studies [1]. We report the fabrication of a microfluidic droplet-based microreactor operating at elevated temperatures (up to 130 °C) and pressures (up to 0.7 MPa), to rapidly study reaction kinetics. As proof-of-principle, the temperature-dependent fluorescence of Rhodamine B in ethanol is monitored [2]. Time-resolved information is obtained by measuring at multiple spots in the microreacto