Fabrication and testing of polydimethylsiloxane (PDMS) microchannel for lab-on-chip (LOC) magnetically-labelled biological cells separation

Microfluidics channel of micron-to millimeter in dimension has been widely used for fluid handling in transporting, mixing and separating biological cells in Lab-on-Chip (LoC) applications. In this research, fabrication and testing of Polydimethylsiloxane (PDMS) microfluidic channel for Lab-on-chip magnetically-labelled biological cells separation is presented. The microchannel is designed with one inlet and outlet. A reservoir or chamber is proposed as an extra component of the microchannel design for ease of trapping the intended biological cells in LoC magnetic separator system. The PDMS microchannel of circular-shaped chamber geometry has been successfully fabricated using replica molding technique from SU-8 negative photoresist mold. An agglomerate-free microbeads flowing has been observed using the fabricated PDMS microchannel. Trapping of microbeads in the trapping chamber with 2.0 A current supply in the continuous microfluidics flow > 100 µL/min has also been demonstrated. In conclusion, a separation of biological cells labelled with magnetic microbeads is expected to be realized using the fabricated PDMS microchannel

Joule heating effect reduction of an electromagnet system utilizing on-chip magnetic core

Joule heating effect is substantial in an electromagnet system due to high density current from current-carrying conductor for high magnetic field generation. In Lab-on-chip (LoC) Magnetically Activated Cell Sorting (MACS) device, Joule heating effect generating high temperature and affecting the biological cells viability is investigated. The temperature rise of the integrated system was measured using resistance temperature detector, RTD Pt100. Three temperature rise conditions which are from the bare spiral-shaped magnet wire, the combination of magnet wire and on-chip magnetic core and combination of magnet wire, on-chip magnetic core and 150 µm polydimethylsiloxane (PDMS) layer have been investigated. The combination of electromagnet of spiral-shaped magnet wire coil and on-chip magnetic core has reduced the temperature significantly which are, ~ 38 % and ~ 26 % with magnet wire winding, N = 10 (IDC = 3.0 A, t = 210 s) and N = 20 (IDC = 2.5 A, t = 210 s) respectively. The reduced Joule heating effect is expected due to silicon chip of high thermal conductivity material enable fast heat dissipation to the surrounding. Therefore, the integration of electromagnet system and on-chip magnetic core has the potential to be used as part of LoC MACS system provided the optimum operating conditions are determined

Selection of High Strength Encapsulant for MEMS Devices Undergoing High Pressure Packaging

Deflection behavior of several encapsulant materials under uniform pressure was studied to determine the best encapsulant for MEMS device. Encapsulation is needed to protect movable parts of MEMS devices during high pressure transfer molded packaging process. The selected encapsulant material has to have surface deflection of less than 5 ?m under 100 atm vertical loading. Deflection was simulated using CoventorWare ver.2005 software and verified with calculation results obtained using shell bending theory. Screening design was used to construct a systematic approach for selecting the best encapsulant material and thickness under uniform pressure up to 100 atm. Materials considered for this study were polyimide, parylene C and carbon based epoxy resin. It was observed that carbon based epoxy resin has deflection of less than 5 ?m for all thickness and pressure variations. Parylene C is acceptable and polyimide is unsuitable as high strength encapsulant. Carbon based epoxy resin is considered the best encapsulation material for MEMS under high pressure packaging process due to its high strength.Comment: Submitted on behalf of EDA Publishing Association (http://irevues.inist.fr/EDA-Publishing

TRIBOLOGY IN BIOLOGY: BIOMIMETIC STUDIES ACROSS DIMENSIONS AND ACROSS FIELDS

ABSTRACT Biomimetics is a field that has the potential to drive major technical advances. It might substantially support successful mastering of current tribological challenges, i.e., friction, adhesion and wear in machines and devices from the meter to the nanometer scale. Science currently goes through a major change, with biology gaining increasing importance. Indeed, biology is becoming the new Leitwissenschaft. Tribology is omnipresent in biology. Various examples for biological tribosystems across dimensions are introduced to the reader, exemplifying the hierarchical nature of biomaterials, and concepts such as integration instead of additive construction, optimization of the whole instead of maximization of a single component feature, multifunctionality instead of mono-functionality and development via trial-and-error processes. The current state of biomimetics in tribology is reviewed, and possible biomimetic scenarios to overcome current tribological challenges are suggested (switchable adhesives, micromechanic devices, novel lubricants and adhesives)

Enhancement and reproducibility of high quality factor, one-dimensional photonic crystal/photonic wire (1D PhC/PhW) microcavities

Background: The production of compact and multi-functional photonic devices has become a topic of major research activity in recent years. Devices have emerged that can be used for functional requirements in high speed optical data processing, filtering, nonlinear optical functions such as all-optical switching - and many other applications. The combination of photonic crystal (PhC) structures consisting of a single row of holes embedded in a narrow photonic wire (PhW) waveguide realised in high index-contrast materials is a possible contender for provision of a range of compact devices on a single chip. This trend has been motivated by the availability of a silicon technology that can support monolithic integration to form fully functional devices on CMOS chips. Results: We have successfully demonstrated experimentally an enhancement of the quality factor of a one-dimensional (1D) photonic crystal/photonic wire (PhC/PhW) microcavity that can exhibit resonance quality factor (Q-factor) values as high as 800,000 - together with a low modal volume of approximately 0.5 (λ/n)3. These results are based on the use of a mode matching approach previously used for device design - through the engineering of tapered hole sections within and outside the cavity - and were achieved without removing the silica cladding layer below the silicon waveguide core. The simulation results obtained in this case also agree with the experimental results obtained. Conclusions: In this work we have demonstrated that the mode matching, as light enters the photonic crystal structure, can be further enhanced through the use of careful fine tuning of the third hole, t3 of the tapered hole region outside the cavity. The Q-factor value obtained was approximately four times greater than that achieved in our previous work on a similar structure

Приклади завдань для позакласної роботи з інформатики у початковій школі

У статті коротко описана методика проведення позакласної роботи з інформатики у початковій школі

Efficient magnetic microbeads trapping using lab-on-chip magnetic separator

Lab-on-Chip (LoC) magnetic separation is a simple and effective method in separating bioparticles labelled with magnetic microbeads in microfluidics flow condition. In this work, trapping efficiency of magnetic microbeads using LoC magnetic separator and a microfluidics channel with chamber design is determined. The polydimethylsiloxane (PDMS) microfluidics channel was designed with an inlet, an outlet and a circular trapping chamber at the center. Standard soft lithography technique was used to replicate the PDMS microfluidics channel from the SU-8 mould. In a continuous hydrodynamics flow of 1.0 μL/min, trapping efficiency of 99.5 % and 94.9 % for 4.5 μm and 2.5 μm magnetic microbeads respectively was achieved. Flow analysis using COMSOL Multiphysics has been conducted in predicting the possible location of the magnetic beads trapping inside the microfluidics channel. The trapping is possible whenever the magnetic force is larger than the drag force experience by the magnetic microbead. The microfluidics channel with chamber design had facilitated low hydrodynamics drag force on the magnetic beads and resulted high efficiency trapping. Therefore, the development of this LoC magnetic separator may be promising to be utilized for biological studies and point-of-care testing (POCT) applications