Effect of hydrofluoric acid (HF) concentration to pores size diameter of silicon membrane

J. Micromech. Microeng.

et al. 2017

This paper presents a technique for separating biological molecules in mixture using nanoporous silicon membrane. Nanopores were formed using electrochemical etching process (ECE) by etching a prefabricated silicon membrane in hydrofluoric acid (HF) and ethanol, and then directly bonding it with PDMS to form a complete filtration system for separating biological molecules. Tygon S3™ tubings were used as fluid interconnection between PDMS molds and silicon membrane during testing. Electrochemical etching parameters were manipulated to control pore structure and size. In this work, nanopores with sizes of less than 50 nm, embedded on top of columnar structures have been fabricated using high current densities and variable HF concentrations. Zinc oxide was diluted with deionized (DI) water and mixed with biological molecules and non-biological particles, namely protein standard, serum albumin and sodium chloride. Zinc oxide particles were trapped on the nanoporous silicon surface, while biological molecules of sizes up to 12 nm penetrated the nanoporous silicon membrane. The filtered particles were inspected using a Zetasizer Nano SP for particle size measurement and count. The Zetasizer Nano SP results revealed that more than 95% of the biological molecules in the mixture were filtered out by the nanoporous silicon membrane. The nanoporous silicon membrane fabricated in this work is integratable into bio-MEMS and Lab-on-Chip components to separate two or more types of biomolecules at once. The membrane is especially useful for the development of artificial kidney.

Section: Pore Characterizationmentioning

confidence: 97%

“…For our application, the pore holes has to be columnar, with pore sizes of less than 50 nm. Our previous work has shown that pore sizes and uniformity are reproducible given the specific set of parameters [33,40,41].…”

Section: Ece Processmentioning

confidence: 99%

Electrochemically etched nanoporous silicon membrane for separation of biological molecules in mixture

Burham

Hamzah

J. Micromech. Microeng.

et al. 2017

“…The aim of this research was to separate biological particles from the membranes for use as an artificial kidney. It has been noted in a previous research work by (Burham et al 2014a(Burham et al , 2014b) that the silicon membranes had some flaws as the biological particles tend to clog. Therefore, application of dielectrophoresis will be used to improve and separate the biological particles.…”

Section: Introductionmentioning

confidence: 95%

3-Dimensional Electric Field Distributions of Castellated and Straight Dielectrophoresis Electrodes for Cell Separation

Yunus

Buyong

et al. 2019

JSM

Self Cite

This paper discusses the 3-dimensional (3D) electric field distributions on the surface and across the bulk volume of dielectrophoresis (DEP) electrodes. The importance of obtained high electric field is to ensure that biological particles will be able to separate even at low voltage potentials in order to avoid damage to the biological particles. Two electrodes-straight and castellated, were designed using the COMSOL Multiphysics Software Version 5.2 to compare the surface distribution and volume electric fields along the x, y and z axes. The results showed that castellated electrodes showcased higher electric fields for both the surface and volume factors along all axes. The maximum value of volume electric field results was 3.94×10 5 V/m along the x-axis, 3.80×10 5 V/m along the y-axis and 1.65×10 5 V/m along the z-axis. The maximum value of surface electric fields distributions was 3.39×10 5 V/m along the x-axis, 2.87×10 5 V/m along the y-axis and 1.14×10 5 V/m along the z-axis. Additionally, the uniformity of the electric field lines distribution from the COMSOL Multiphysics also indicated that castellated electrodes have a much higher uniformity. The experimental results showed that the castellated electrodes separated particles much faster at 69 s, as compared to straight electrodes at 112 s. Henceforth, this has proven that castellated electrodes have a high electric field as it separates much faster as compared to straight electrodes.

“…Various methods to realize a nano size filtration trench have been reported before. As an example, Burham et al (2014) uses electrochemical etching to form nano scale trenches but then the produced trenches are not uniform in size plus challenging to reproduce precise same trench size and trench-to-trench gap which is not favorable for mass production. In the other hand, for the fabrication of uniform trenches; electron beam lithography, focused ion beam etching, and nanoimprint lithography might be used (Nabar et al 2012;Tong et al 2004).…”

Section: Introductionmentioning

confidence: 99%

Fabrication of Micromachined Uniform Microtrench Arrays for Silicon based Filtration Membrane

Mustafa

Majlis

et al. 2019

JSM

Self Cite

In this paper, we report a uniform microtrench array fabricated on silicon substrate. The proposed system is aimed for the biological molecules separation process via filtration in artificial kidney. The system consists of silicon based membrane having arrays of trench with the dimension of approximately 1 µm. The fabrication of the trenches is following standard silicon MEMS process with additional surface modification of the fabricated trench by using thermal oxidation process. The result shows that trench patterns having size of 1~2 µm have been produced. The thermal oxidation process shows that the trench size could be reduced up to 50%. The study will be beneficial for the development of silicon membrane with uniform microtrench arrays for application in filtration of blood cell from other solutes based on molecule size. When the microtrench is etched through the silicon membrane, a filtration membrane is then formed. The separation of solutes will be better due to the uniform size of microtrench.