Rapid photothermal actuation of light-addressable, arrayed hydrogel columns in a macroporous silicon membrane

Macroporous silicon is a type of porous silicon that has ordered arrays of channels with high aspect ratio. Macroporous silicon with ordered 3-D structures have a variety of applications such as filters for a particle separation, photonic crystals and optical shortpass filters because of their spatially periodic structures [1–3]. These structures can be prepared by the electrochemical etching (ECE) of silicon wafers in hydrofluoric acid (HF). We report here a way to fabricate macroporous silicon membranes with ordered 3D structures that have controlled periodicity and dimensions appropriate for cell sorting. The silicon 3D structures have pores with variable diameters to modulate the flow behavior and optimize cell sorting efficiency. The silicon membranes were fabricated by wet etching of n-type (100) silicon substrate (40–60 W cm) in potassium hydroxide (KOH) solution with isopropyl alcohol at 80 °C. The 3-D structures were prepared by the electrochemical etching (ECE) of the membranes in diluted HF using the backside illumination with modulated intensity. The thickness of the fabricated membrane has been varied from 20 to 200 mm to optimize filtration of the cells by MEMS (Micro-ElectroMechanical Systems) chips designed for biological cell sorting and cell positioning. The software packages IntelliSuite and ANSYS FLOWTRAN were used to study the mechanical strength of the membrane as well as the velocity profile and flow behavior of Newtonian fluids inside the macroporous silicon membrane.

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Active liquid flow control through a polypyrrole-coated macroporous silicon membrane toward chemical stimulation applications

Sensors and Actuators A Physical ◽

10.1016/j.sna.2020.112512 ◽

2021 ◽

Vol 318 ◽

pp. 112512

Author(s):

Hojjat Rostami Azmand ◽

Amarachukwu N. Enemuo ◽

Sang-woo Seo

Keyword(s):

Flow Control ◽

Liquid Flow ◽

Chemical Stimulation ◽

Macroporous Silicon ◽

Silicon Membrane ◽

Active Liquid

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Strain measurement by means of bend contour microscopy

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100153026 ◽

1989 ◽

Vol 47 ◽

pp. 210-211

Author(s):

Philip D. Hren

Keyword(s):

Strain Measurement ◽

Large Angle ◽

Single Crystal Silicon ◽

Convergent Beam Electron Diffraction ◽

Zone Axis ◽

Silicon Membrane ◽

Crystal Silicon ◽

Contour Pattern ◽

Convergent Beam ◽

Low Symmetry

The pattern of bend contours which appear in the TEM image of a bent or curled sample indicates the shape into which the specimen is bent. Several authors have characterized the shape of their bent foils by this method, most recently I. Bolotov, as well as G. Möllenstedt and O. Rang in the early 1950’s. However, the samples they considered were viewed at orientations away from a zone axis, or at zone axes of low symmetry, so that dynamical interactions between the bend contours did not occur. Their calculations were thus based on purely geometric arguments. In this paper bend contours are used to measure deflections of a single-crystal silicon membrane at the (111) zone axis, where there are strong dynamical effects. Features in the bend contour pattern are identified and associated with a particular angle of bending of the membrane by reference to large-angle convergent-beam electron diffraction (LACBED) patterns.

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