Electroplating is an important step in microfabrication in order to increase thickness of undersized parts up to a few micrometers with a low-cost, fast method that is easy to carry out, especially for metals such as copper, nickel, and silver. This important step promotes the development of the fabrication technology of electronic devices on a flexible substrate, also known as flexible electronic devices. Nevertheless, this technology has some disadvantages such as low surface uniformity and high resistivity. In this paper, parameters of copper electroplating were studied, such as the ratio of copper (II) sulfate (CuSO 4 ) concentration to sulfuric acid (H 2 SO 4 ) concentration and electroplating current density, in order to obtain low resistivity and high surface uniformity of the copper layer. Samples were characterized by scanning electron microscopy (SEM), four-point probe, and surface profiler. The results showed that the sample resistivity could be controlled from about 2.0 to about 3.5 μΩ • cm, and the lowest obtained resistivity was 1.899 μΩ • cm. In addition, surface uniformity of the electroplated copper layer was also acceptable. The thickness of the copper layer was about 10 μm with an error of about 0.5 μm. The most suitable conditions for the electroplating process were CuSO 4 concentration of 0.4 mol l −1 , H 2 SO 4 concentration of 1.0 mol l −1 , and low electroplating current density of 10-20 mA cm −2 . All experiments were performed on a flexible polyethylene terephthalate (PET) substrate.

This paper presents the entire fabrication process including photolithography, sputtering, deep reactive ion etching (Bosch DRIE process) on silicon substrate and bonding process between the lid and silicon substrate to create a designed filtration microfluidic chip with dimension of 28 mm × 7 mm, one inlet port and one outlet port. A pattered silver thin film was deposited on a silicon sample by the lift-off method. Subsequently the newly fabricated sample was anisotropically etched by Bosch DRIE process. Some parameters of Bosch DRIE process such as bias power, duration of etching step and passivation step, oxygen presence were studied to explore the dependence of silicon channel depth and etched shape profile on these parameters. An optimized process was utilized to fabricate a featured silicon channel with vertical, smooth sidewalls and an overall good uniformity. The silicon channel has four arrays of microposts with various distances between microposts from 25 μm to 100 μm. The depth of the silicon channel was about 150 μm. After that, silicon substrate was bonded with mica lid by adhesive bonding method to form the completed filtration microfluidic chip. The samples were characterized by scanning electron microscopy (SEM), mechanical profilometer (DEKTAK 6 M), optical microscopy (Olympus MX51). In this paper a test was performed to demonstrate how the microfluidic chip works by pumping solution with many various sizes of particles through the inlet port of the microfluidic chip and obtaining a solution with desired particles sizes (smaller than 25 μm) through another port. Moreover, the chip could be pumped de-ionized water through outlet port for backwash in order to make this microfluidic chip reusable. Finally, a few applications of microfluidic chips are presented to illustrate the advantages of this technology and the potential for future development.

In this paper silver-assisted chemical etching (SACE) was studied to increase roughness and reduce light reflection from the surface of n-type (100) mono-crystalline silicon. SACE process includes two basic steps which are silver deposition and chemical etching step. Simple electroless silver deposition step using mixture of AgNO 3 and HF was utilized to form silver nanoparticles onto n-type silicon surface. Following chemical etching step was carried out by immersing samples in mixture of HF and H 2 O 2 . Concentration of AgNO 3 in eletroless deposition step and concentration of HF in chemical etching step were investigated to get minimum reflectance. The surface of sample was characterized by scanning electron microscopy (SEM), field emission scanning electron microscopy (FE-SEM) and sample reflectance was measured at the wavelength range from 350-1100 nm. The results show that reflectance depends on AgNO 3 concentration in electroless deposition step and HF concentration in etching step and the minimum solar-weighted reflectance is 1.74%. This method can be considered as simple, inexpensive method to effectively increase roughness and suppress light reflection for photovoltaic, optoelectronic, sensor, photonic applications.