Micro- and nano-fabrication methods facilitate the use of nanostructures for the separation of collections of particles and nanobio-based optical and electrochemical sensing. We have presented an easy and simple nanopore size reduction method of a low-stressed silicon nitride (SiN ) membrane nanosieve (100×100 μm 2 ) using a nanoimprinting method based on a natural thermal reflow of the contact imprinting polymer, possibly maintaining compatibility with complementary metal-oxide semiconductor integrated circuit processes. The nanopore pattern size of this nanosieve membrane was precisely patterned by a nanoimprinting process using an electron beam patterned silicon master, to about 30-nm diameter. By employing mainly an electron beam resist reflow phenomena after a nanoimprinting process and anisotropic reactive ion etch, the etch holes’ size was fabricated to be the same with nanopatterns on the polymer. The contact imprinting master can be used continually for the generation of nanopore patterns simply and easily. It can endure harsh conditions like high temperature up to 800°C, and it is inert to many aggressive and strong chemicals. Also, this would be a low-cost, simple, and easy fabrication method for the precise and reliable size-reduction control of nanopores for mass production of nanobio sensors or chips.
Micro- and Nano-fabricated membrane sieves have a great potential in molecular separation applications by giving more
precise structural and pattern control of shapes. This limitation can be addressed by a class of ultrathin membranes for
molecular separations in solutions. Micromachining methods facilitate the accomplishing nanostructures to be used for
separation of collections of particles. It makes possible to fabricate nanosieves having a thickness on the order of or even
smaller than the diameter of the nanohole [1-2]. However, membrane fragility and complex fabrication have prevented
the use of ultrathin membranes for molecular separations [3-4]. Furthermore, it is difficult to control the holes in nanoscale
dimensions precisely and uniformly for mass production. Even though there are few reports on the size control of
nanopores of the membrane nanosieves, it is necessary to do research on the precise and reliable size control of
nanopores for mass production of biosensors or biochips.
This paper describes the pure passive scheme that manipulates the multiple streams using microfluidic device. This device relies on capillarity to control merging of two streams and to regulate the volumetric flow rate (VFR). This sophisticated manipulation of the capillarity is, however, nontrivial due to the lack of the passive and precise means. Here, we control the capillarity precisely and rapidly through the geometry of the junction of two streams and the hydrophilicity of the substrate. Additionally, we use the relative flow resistance to control the VFR ratio of the merged two streams. This passive scheme leads to the significant simplification of the control of the multistream without sacrificing the rapidity and precision. When combined with the microfluidic components such as mixers, reaction chambers, and detectors, this passive scheme offer the possibility of designing disposable and integrated microfluidic systems.
We present a novel technology for a cyclo-olefin-copolymer (COC) plastic microfluidic platform for heat control with fully semiconductor process-compatible photolithographic 5 μm-wide metal patterns, for heaters, electrodes, and temperature sensors and a thin membrane structure. Through tests of compatibility of some thermoplastic materials with chemical solutions and temperature tolerance to the semiconductor processes (thin film depositions, photolithography, and etchings), we selected COC as a semiconductor process-compatible plastic material for biomedical applications. For photolithography processes, we manufactured the 5’ COC wafer with flat surface with c.a. 3 nm surface roughness, employing a novel flame-torched injection-molding method. Furthermore, the part of heating blocks on COC wafers is controlled thickness to the 100 μm, to enhance the heat-ramping speeds through reduction of the thermal mass. In order to fabricate the Au thin film micro-patterns for temperature sensors, heaters, and electrodes, Au film (100 nm) was deposited by e-beam evaporator and patterned by using standard photolithography, and wet-etched. The micro-patterned Au temperature sensors, heaters, and electrodes was demonstrated. For insulating layers, Al<sub>2</sub>O<sub>3</sub> film was deposited by an ALD system, patterned by using the standard photolithography, and wet-etched. Using the COC microfluidic platform, we tested thermal cycling with simple heating and natural cooling on chip with water and, heating rates (5°C/s when heating, 3°C/s when cooling) are obtained. Therefore, the COC microfluidic platform can be applied to a DNA lab-on-a-chip.
A novel polymer microfluidic device for self-wash using only capillary force is presented. A liquid filled in a reaction chamber is replaced by another liquid with no external actuation. All the fluidic actuations in the device is pre-programmed about time and sequence, and accomplished by capillary force naturally. Careful design is necessary for exact actions. The fluidic conduits were designed by the newly derived theoretical equations about the capillary stop pressure and flow time. Simulations using CFD-ACE+ were conducted to check the validity of theory and the performance of the chip. These analytic results were consistent with experimental ones. The chip was made of polymers for the purpose of single use and low price. It was fabricated by sealing the hot-embossed PMMA substrate with a PET film. For simpler fabrication, the chip was of a single height. The embossing master was produced from a nickel-electroplating on a SU8-patterned Ni-plate followed by CMP. The contact angles of liquids on substrates were manipulated through the mixing of surfactants, and the temporal variations were monitored for a more exact design. The real actuation steps in experiment revealed the stable performance of selfwash, and coincided well with the designed ones. The presented microfluidic method can be applicable to other LOCs of special purposes through simple modification. For example, array or serial types would be possible for multiple selfwashes.