Simple Polydimethylsiloxane Research Articles

High throughput fabrication of disposable nanofluidic lab-on-chip devices for single molecule studies.

An easy method is introduced allowing fast polydimethylsiloxane (PDMS) replication of nanofluidic lab-on-chip devices using accurately fabricated molds featuring cross-sections down to 60 nm. A high quality master is obtained through proton beam writing and UV lithography. This master can be used more than 200 times to replicate nanofluidic devices capable of handling single DNA molecules. This method allows to fabricate nanofluidic devices through simple PDMS casting. The extensions of YOYO-1 stained bacteriophage T4 and λ-DNA inside these nanochannels have been investigated using fluorescence microscopy and follow the scaling prediction of a large, locally coiled polymer chain confined in nanochannels.

Toward CMOS image sensor based glucose monitoring

Complementary metal oxide semiconductor (CMOS) image sensor is a powerful tool for biosensing applications. In this present study, CMOS image sensor has been exploited for detecting glucose levels by simple photon count variation with high sensitivity. Various concentrations of glucose (100 mg dL(-1) to 1000 mg dL(-1)) were added onto a simple poly-dimethylsiloxane (PDMS) chip and the oxidation of glucose was catalyzed with the aid of an enzymatic reaction. Oxidized glucose produces a brown color with the help of chromogen during enzymatic reaction and the color density varies with the glucose concentration. Photons pass through the PDMS chip with varying color density and hit the sensor surface. Photon count was recognized by CMOS image sensor depending on the color density with respect to the glucose concentration and it was converted into digital form. By correlating the obtained digital results with glucose concentration it is possible to measure a wide range of blood glucose levels with great linearity based on CMOS image sensor and therefore this technique will promote a convenient point-of-care diagnosis.

Amperometric Detection of Parathion and Methyl Parathion with a Microhole‐ITIES

AbstractAn amperometric sensor featuring a microhole‐liquid/gel interface for the detection of both parathion and methyl parathion is developed on the basis of their different kinetics behavior when interacting with the enzyme organophosphorus hydrolase (OPH). OPH hydrolyzes parathion and methyl parathion producing a common product of para‐nitrophenol and either diethylthio‐ or dimethylthio‐ phosphoric acid, respectively, of which all can release protons depending upon their pKa values. The detection method for both organophosphate (OP) compounds is designed to measure the current associated with the transfer of protons released from the products of OPH hydrolysis across a polarized microhole‐water/polyvinylchloride‐nitrophenyloctylether (PVC‐NOPE) gel interface. The selective transfer of protons across the interface is tailored by the use of a proton selective ligand, ETH 1778, in the gel layer. A disposable proton selective sensor that can quantitatively analyze the OP compounds is also fabricated using simple polydimethylsiloxane microfabrication. Cyclic voltammetry and differential pulse stripping voltammetry are first utilized to characterize the transfer of protons across the microhole‐water/PVC‐NPOE gel interface initiated by the OPH reaction with parathion and methyl parathion and to establish a detection limit for each OP compound. In order to sequentially detect parathion and methyl parathion using a single proton selective strip‐sensor, a novel time‐resolved detection methodology is developed based on the different catalytic kinetics of OPH with each OP analyte; the maximum peak current for the preconcentrated protons transferring back from the organic to water phase assisted by ETH 1778 increases proportionally to the concentration of each OP agent. Since the maximum peak currents for both OP analytes are observed at different reaction times it was possible to demonstrate the multiplexed analysis of both parathion and methyl parathion down to 0.5 µM using a single sensor.

Amperometric proton selective strip-sensors with a microelliptic liquid/gel interface for organophosphate neurotoxins

A novel strip-based disposable amperometric proton sensor that can selectively detect organophosphate neurotoxins ( i.e., paraoxon) is described. The detection methodology is based on measuring the current change involved in the assisted proton transfer by a proton selective ligand ( e.g., ETH 1778) across a microelliptic hole interface between the aqueous and polyvinylchloride-2-nitrophenyloctylether gel phase. The selective detection of paraoxon is achieved by measuring protons released by the specific hydrolysis of paraoxon with the organophosphorus hydrolase enzyme. A two-step process involving the hydrolysis and proton transfer reaction was characterized using cyclic voltammetry and differential pulse stripping voltammetry. A strip-based sensor fabricated using a simple polydimethylsiloxane (PDMS) mold with the resulting device was found to exhibit a linear response over a wide range of paraoxon concentrations (0.5 μM–100 μM) present in aqueous samples. In addition to the excellent detection limit and a wide dynamic range, a superb selectivity in the presence of common interfering agents in agricultural samples is achieved.

Simultaneous positioning and orientation of a single nano-object by flow control: theory and simulations

In this paper, we theoretically describe a method to simultaneously control both the position and orientation of single nano-objects in fluids by precisely controlling the flow around them. We develop and simulate a control law that uses electro-osmotic flow (EOF) actuation to translate and rotate rigid nano-objects in two spatial dimensions. Using EOF to control nano-objects offers advantages as compared to other approaches: a wide class of objects can be manipulated (no magnetic or electric dipole moments are needed), the object can be controlled over a long range (>100 μm) with sub-micrometer accuracy, and control may be achieved with simple polydimethylsiloxane (PDMS) devices. We demonstrate the theory and numerical solutions that will enable deterministic control of the position and orientation of a nano-object in solution, which can be used, for example, to integrate nanostructures in circuits and orient sensors to probe living cells.

542 柔軟マイクロアクチュエータの医療応用(T05 マイクロ・ナノ技術のロボティクス応用,大会テーマセッション,21世紀地球環境革命の機械工学:人・マイクロナノ・エネルギー・環境)

This paper presents a retractor as one of micro surgical tools, which was realized by applying flexible micro actuator. The refractor holds the abdominal organ to the side during the entire operation to keep the sight and operational space in endoscopic surgery. The retractor is actuated by PBA (Pneumatic Balloon Actuator), which is featured its small, soft and safe characteristics. PBA is fabricated through the simple PDMS (polydimethylsiloxane) molding process and pneumatically driven. That is to say, it is possible to hold the organ to the side safely. We researched characteristics of retractor, and verified removal of abdominal organ from the experiment on a living rabbit.

Simple Patterning via Adhesion between a Buffered‐Oxide Etchant‐Treated PDMS Stamp and a SiO2 Substrate

AbstractA very simple polydimethylsiloxane (PDMS) pattern‐transfer method is devised, called buffered‐oxide etchant (BOE) printing. The mechanism of pattern transfer is investigated, by considering the strong adhesion between the BOE‐treated PDMS and the SiO2 substrate. PDMS patterns from a few micrometers to sub‐micrometer size are transferred to the SiO2 substrate by just pressing a stamp that has been immersed in BOE solution for a few minutes. The patterned PDMS layers work as perfect physical and chemical passivation layers in the fabrication of metal electrodes and V2O5 nanowire channels, respectively. Interestingly, a second stamping of the BOE‐treated PDMS on the SiO2 substrate pre‐patterned with metal as well as PDMS results in a selective transfer of the PDMS patterns only to the bare SiO2. In this way, the fabrication of a device structure consisting of two Au electrodes and V2O5 nanowire network channels is possible; non‐ohmic semiconducting I–V characteristics, which can be modeled by serially connected percolation, are observed.