Showing papers on "Microchannel published in 2001"
TL;DR: The ability to confine liquid flow inside microchannels with only two physical walls is expected to be useful in applications where a large gas- liquid interface is critical, as demonstrated here by a gas-liquid reaction.
Abstract: Self-assembled monolayer chemistry was used in combination with either multistream laminar flow or photolithography to pattern surface free energies inside microchannel networks. Aqueous liquids introduced into these patterned channels are confined to the hydrophilic pathways, provided the pressure is maintained below a critical value. The maximum pressure is determined by the surface free energy of the liquid, the advancing contact angle of the liquid on the hydrophobic regions, and the channel depth. Surface-directed liquid flow was used to create pressure-sensitive switches inside channel networks. The ability to confine liquid flow inside microchannels with only two physical walls is expected to be useful in applications where a large gas-liquid interface is critical, as demonstrated here by a gas-liquid reaction.
771 citations
TL;DR: In this paper, a packed-bed microchemical system consisting of a microfluidic distribution manifold, a microchannel array, and a 25-μm microfilter for immobilizing solid particulate material within the reactor chip and carrying out different heterogeneous chemistries is presented.
Abstract: A microchemical device has been built in silicon and glass by using microfabrication methods including deep-reactive-ion etch technology, photolithography, and multiple wafer bonding. The microchemical system consists of a microfluidic distribution manifold, a microchannel array, and a 25-μm microfilter for immobilizing solid particulate material within the reactor chip and carrying out different heterogeneous chemistries. Multiple reagent streams (specifically, gas and liquid streams) are mixed on-chip, and the fluid streams are brought into contact by a series of interleaved, high-aspect-ratio inlet channels. These inlet channels deliver the reactants continuously and cocurrently to 10 reactor chambers containing standard catalytic particles. The performance of the microfabricated “packed-bed” reactor is compared to that of traditional multiphase packed-bed reactors in terms of fluid flow regimes, pressure drop, and mass transfer. The hydrogenation of cyclohexene is used as a model reaction to measure t...
445 citations
TL;DR: The device was used to detect the separation of a mixture of proteins and small molecules by capillary electrophoresis; the separation illustrated the suitability of this integrated fluorescence detection system for bioanalytical applications.
Abstract: This paper describes a prototype of an integrated fluorescence detection system that uses a microavalanche photodiode (μAPD) as the photodetector for microfluidic devices fabricated in poly(dimethylsiloxane) (PDMS). The prototype device consisted of a reusable detection system and a disposable microfluidic system that was fabricated using rapid prototyping. The first step of the procedure was the fabrication of microfluidic channels in PDMS and the encapsulation of a multimode optical fiber (100-μm core diameter) in the PDMS; the tip of the fiber was placed next to the side wall of one of the channels. The optical fiber was used to couple light into the microchannel for the excitation of fluorescent analytes. The photodetector, a prototype solid-state μAPD array, was embedded in a thick slab (1 cm) of PDMS. A thin (80 μm) colored polycarbonate filter was placed on the top of the embedded μAPD to absorb scattered excitation light before it reached the detector. The μAPD was placed below the microchannel an...
440 citations
04 Nov 2001
TL;DR: In this paper, a delay-line read-out technique for microchannel plate detectors with an increased acceptance for multiple hit events compared to standard two-layer delayline anodes is presented.
Abstract: We have developed a delay-line read-out technique for microchannel plate detectors with an increased acceptance for multiple hit events compared to standard two-layer delay-line anodes. This technique allows unambiguous determination of arrival time and position of at least four simultaneously detected particles, and/or to detect an even larger number of particles in a shower, as long as any two particles do not arrive both at the same time and at the same position within certain limits. We demonstrate and discuss the abilities and limitations of this technique and the relevance for certain experimental tasks.
264 citations
TL;DR: This study demonstrates the rapid measurement of diffusion coefficients of large and small molecules in a microfluidic device, the T-sensor, by means of conventional epifluorescence microscopy.
225 citations
TL;DR: In this article, a transparent micro-channel heat-sink system was fabricated by bonding glass to a silicon wafer, which consisted of a microchannel array, a heater, and a temperature sensor array.
Abstract: Micromachining technology was utilized to fabricate a transparent microchannel heat-sink system by bonding glass to a silicon wafer. The micro heat sink consisted of a microchannel array, a heater, and a temperature sensor array. This integrated microsystem allowed simultaneous qualitative visualizations of the flow pattern within the microchannels and quantitative measurements of temperature distributions, flow rates, and input power levels. Boiling curves of temperature as a function of the input power were established. No boiling plateau was observed in the boiling curves, consistent with our previously reported data but different from results reported for macrochannel heat sinks. Three stable boiling modes, depending on the input power level, have been distinguished from the flow patterns. Local nucleation boiling was observed in microchannels with a hydraulic diameter as small as 26 /spl mu/m at the lower input power range. At the higher input power range, a stable annular flow was the dominant boiling mode. Bubbly flow, commonly observed in macrochannels, could not be developed in the present microchannels. Consequently, no boiling plateau was detected in the boiling curves.
223 citations
TL;DR: In this article, crossflow and counterflow micro heat exchangers with microchannel or microcolumn structures have been developed for throughputs up to 7 t water/h with a heat transmission power up to 200 kW.
Abstract: Metallic microstructure devices have been manufactured and tested for applications in technical applications in thermal and chemical process engineering and in the laboratory. Manufacturing has been performed by micromachining of metal foils and diffusion bonding of a laminated foil stack, followed by welding of the microstructured core into a housing. Crossflow and counterflow micro heat exchangers with microchannel or microcolumn structures have been developed for throughputs up to 7 t water/h with a heat transmission power up to 200 kW. Overall heat transfer coefficients up to 54,000 W/m2 K have been determined with water as test fluid. Electrically driven microstructured heaters have been developed for fast and precise heating of sensitive liquids or gases. The heater has been used as an evaporator as well. Static micromixers have been developed for fast and complete mixing of reactands. They can be utilized with parallel reactions, for example, to decrease the yield of undesired by-products. For hete...
217 citations
Patent•
19 Dec 2001
TL;DR: In this paper, the onset of clotting is determined by measuring the rate of change or value of capacitance or impedance between two electrodes situated on either side of the microchannel.
Abstract: A device and method for measuring the clotting times in a fluid, typically blood, within a microchannel whereby the onset of clotting is determined by measurement of the rate of change or value of capacitance or impedance between two electrodes situated on either side of the microchannel. There is provided a disposable test-strip (100) comprising an upper and lower support (101) and (103). A microchannel (102) is formed into the upper surface of the lower support member (103). A second substrate layer (101) is laminated on top of the support member (103), thereby closing the open microchannel (102). Electrodes (104) are formed on the respective outer surfaces of the substrate layers and coplanar to the channel.
217 citations
TL;DR: In this article, the effect of the geometry on the flow and heat transfer of a computer chip was studied using high-speed video camera and thermal visualization and temperature measurements of the heated device were carried out using infrared thermography.
Abstract: We fabricated a novel thermal microsystem (simulating a computer chip) consisting of a heater, microchannels, inlet and outlet plena and we studied the effect of the geometry on the flow and heat transfer. The vapor-water two-phase flow patterns were observed in the parallel microchannels through a microscope and high-speed video camera. It was observed that hydraulic instabilities occur. Existence of a periodic annular flow was also observed, which consists of a symmetrically distributed liquid ring surrounding the vapor core. Along the microchannel axis, the periodic dry zone appears and develops. The thermal visualization and temperature measurements of the heated device were carried out using infrared thermography. As long as the flow was single phase liquid, the forced convection heat transfer resulted in a moderate irregularity on the heated chip. These temperature differences do not cause damage to a real electronic device. The steady-state heat transfer for different types of microchannels has been studied also at the range of heat flux where phase change of the working fluid from liquid to vapor took place. Under conditions of flow boiling in microchannels, a significant enhancement of heat transfer was established. In the case of uniform heat flux the hydraulic instabilities lead to irregularity of temperature distribution on the heated chip. In the case of nonuniform heat flux the irregularity increased drastically.
213 citations
Patent•
24 Jan 2001
TL;DR: In this article, the authors describe a number of processes and reactions that utilize high heat fluxes to obtain fast, steady-state reaction rates, such as Porous catalysts used in conjunction with micro-channel reactors to obtain high rates of heat transfer.
Abstract: Reactors and processes are disclosed that can utilize high heat fluxes to obtain fast, steady-state reaction rates. Porous catalysts used in conjunction with microchannel reactors to obtain high rates of heat transfer are also disclosed. Reactors and processes that utilize short contact times, high heat flux and low pressure drop are described. Improved methods of steam reforming are also provided.
187 citations
TL;DR: The development of a sandwich immunoassay in disposable plastic microchips that can be reduced to five minutes instead of a few hours in standard microtiterplates due to the small diffusion distances.
Abstract: This paper presents the development of a sandwich immunoassay in disposable plastic microchips. Photoablated microchannels with integrated electrodes have been used for the development of enzyme-linked-immunosorbent-assay (ELISA). The presence of the electrode inside the 40 nL microchannel enables the detection of the redox active enzyme substrate directly inside the reaction channel. Furthermore, due to the small diffusion distances, each incubation time can be reduced to five minutes instead of a few hours in standard microtiterplates. The initial characterisation of this immunoassay has been performed with a large protein complex D-Dimer-alkaline phosphatase. This system was used for the detection of immobilised antibodies on the surface of the photoablated microchannel. In a second step, a sandwich immunoassay with a horseradish peroxidase-secondary antibody conjugate (HRP-conjugate) was used to detect D-Dimer between 0.1 and 100 nM, which is the relevant concentration range
of the clinical tests.
TL;DR: A new system for random separation of a single microorganism, such as a living cell and a microbe, in the microfluidic device under the microscope by integrating the laser‐trapping force and dielectrophoretic (DEP) force is developed.
Abstract: We developed a new system for random separation of a single microorganism, such as a living cell and a microbe, in the microfluidic device under the microscope by integrating the laser-trapping force and dielectrophoretic (DEP) force. An arbitrarily selected single microbe could be isolated in a microchannel, despite the presence of a large number of microbes in solution. Once the target microbe is trapped at the focal point of the laser, we can easily realize exclusion of excess microbes around the target by controlling the electric field, while keeping the target trapped by the laser at the focal point. To realize an efficient separation system, we proposed a new separation cell and produced it by microfabrication. Flow speed in the microchannel is adjusted and balanced to realize high-speed and high-purity extraction of the target. Some preliminary experiments are conducted to show the effectiveness. The target is trapped by the laser, transported, and is taken out from the extraction port. Total separation time is less than 20 s. Our method is extremely useful in the pure cultivation of the cell and will be a promising method for biologists in screening useful microbes.
TL;DR: Signal uniformity, sensitivity, and dynamic range of the detection method were determined, and a unique method for measuring the relaxation time of a chemiluminescent species is also described.
Abstract: Chemiluminescence (CL) detection is seldom used in two-dimensional solid support microarray platforms because adequate sensitivity and spatial resolution is difficult to achieve. The three-dimensional ordered microchannels of the Flow-thru Chip increase both the sensitivity and spatial resolution required for quantitative CL measurements on microarrays. Enzyme-catalyzed CL reactions for the detection of hybridizations on microchannel glass were imaged using a CCD camera. Signal uniformity, sensitivity, and dynamic range of the detection method were determined. The relative standard deviation of signal intensities across an array of 64 spots was 8.1%. A detection limit of 250 amol of target with a linear dynamic range of 3 orders of magnitude was obtained for a 3-h assay. Similar to two-color fluorescence measurements, multiple enzyme labels were employed to demonstrate two-channel chemiluminescence. A unique method for measuring the relaxation time of a chemiluminescent species is also described.
TL;DR: In this paper, the multilayer flow of liquids can be formed in microchannels, where the surface tension and friction force are stronger than the force of gravity, and the interface was observed to be quite stable and to be maintained for a distance of more than 18 cm.
Abstract: We utilized microchip technology and found that the multilayer flow of liquids can be formed in microchannels. Liquid/liquid interfaces were formed parallel to the side wall of the microchannels, because the surface tension and friction force are stronger than the force of gravity. A water/ethylacetate/water interface was formed in a 70-µm-wide and 30-µm-deep channel. The interface was observed to be quite stable and to be maintained for a distance of more than 18 cm. As an example of a multilayer flow application, we demonstrated the liquid/liquid extraction of Co-dimethylaminophenol complex in a microchannel. The solvent-extraction process of the complex into m-xylene in the multilayer flow was found to reach equilibrium in 4 s, while it took 60 s in a simple two-phase extraction.
TL;DR: In this article, a micro-channel reactor specially designed for periodic operation and a process to deposit a catalyst, g-alumina, inside the reactor channels were developed, and the hydrodynamics of the reactor was characterised.
TL;DR: The large specific interfacial areas and short molecular diffusion distances provided by glass microchips play important roles not only for effective phase-transfer synthetic reaction, but also for avoiding an undesirable side reaction as mentioned in this paper.
TL;DR: In this article, a hierarchical ordering over several discrete and tunable length scales ranging from several nanometers to micrometers is proposed for patterned porous materials, which hold promise for use as advanced catalysts, sensors, low-k dielectrics, optoelectronic and integrated photonic crystal devices.
Abstract: A continuing challenge for materials chemists and engineers is the ability to create multifunctional composite structures with well-defined superimposed structural order from nanometer to micrometer length scales. Materials with three-dimensional structures ordered over multiple length scales can be prepared by carrying out colloidal crystallization and inorganic/organic cooperative self-assembly within microchannel networks. The resulting materials show hierarchical ordering over several discrete and tunable length scales ranging from several nanometers to micrometers. These patterned porous materials hold promise for use as advanced catalysts, sensors, low-k dielectrics, optoelectronic and integrated photonic crystal devices.
TL;DR: The design, fabrication, and operation of this new technique of generating on-chip air pressure, used for metering and pumping nanoliter discrete drops in microchannels, are described.
Abstract: A class of “lab-on-a-chip” devices use external air pressure for pumping discrete drops in a microchannel network. External air connectors can be cumbersome and are real-estate intensive. We have developed an on-chip technique to generate pressures required for metering and pumping of nanoliter-volume discrete drops. This is achieved by heating of trapped air in a pressure-generating chamber. The pressure-generating chamber is connected to the point of pressure application in the liquid-conveying microchannel through an air-delivery channel. The trapped air volume on the order of 100 nL is heated by resistive metal heaters by tens of degrees celcius to generate air pressures on the order of 7.5 kN/m2. The rate of discrete drop pumping is electronically controlled in the microchannel device by controlling the rate of air heating. Flow rates on the order of 20 nL/s are obtained in the microchannel (300 μm × 30 μm) by heating the air chamber at the rate of ∼6 °C/s. In this paper, we describe the design, fabr...
TL;DR: In this paper, the mixing of solutes present in a drop moving in a slit-type microchannel is modeled by modeling the mixing process of a discrete liquid drop moving through a flow.
Abstract: Fast solute mixing can be achieved in a microchannel by rapid unidirectional displacement of a discrete liquid drop. The recirculation streamlines created within the liquid during the drop’s motion cause the solute to interlayer across the channel depth, provided the interlayer diffusion of the solute is small. Uniform interlayering appears when the drop is displaced by more than three drop lengths in a slit-type microchannel, thereby reducing the solute diffusion distances to a fraction of the channel depth. By fabricating the microchannel to a depth of less than 50 µm even large molecules with a low diffusivity ( D< 10 −8 cm 2 s −1 ) can be mixed in seconds. The above strategy is shown by modeling the mixing of solutes present in a drop moving in a slit-type microchannel.
TL;DR: In this article, the effects of the hydrophobicity of silicon microchannels and components in the oil and water phases in the production of monodispersed water-in-oil (W/O) emulsions by microchannel emulsification was investigated.
TL;DR: In this paper, the formation of ZSM-5 zeolitic coatings on AISI 316 stainless steel plates with a microchannel structure has been investigated at different synthesis mixture compositions.
Abstract: An elegant way to prepare catalytically active microreactors is by applying a coating of zeolite crystals onto a metal microchannel structure. In this study the hydrothermal formation of ZSM-5 zeolitic coatings on AISI 316 stainless steel plates with a microchannel structure has been investigated at different synthesis mixture compositions. The procedures of coating and thermal treatment have also been optimized. Obtaining a uniform thickness of the coating within 0.5 mm wide microchannels requires a careful control of various synthesis variables. The role of these factors and the problems in the synthesis of these zeolitic coatings are discussed. In general, the synthesis is most sensitive to the H2O/Si ratio as well as to the orientation of the plates with respect to the gravity vector. Ratios of H2O/Si=130 and Si/template=13 were found to be optimal for the formation of a zeolitic film with a thickness of one crystal at a temperature of 130°C and a synthesis time of about 35 h. At such conditions, ZSM-5 crystals were formed with a typical size of 1.5 μm×1.5 μm×1.0 μm and a very narrow (within 0.2 μm) crystal size distribution. The prepared samples proved to be active in the selective catalytic reduction (SCR) of NO with ammonia. The activity tests have been carried out in a plate-type microreactor. The microreactor shows no mass transfer limitations and a larger SCR reaction rate is observed in comparison with pelletized Ce-ZSM-5 catalysts.
Patent•
30 Jul 2001
TL;DR: In this article, a media content capture and distribution system includes at least one capture system which provides clips of media content satisfying a set of at least 1 trigger defined for the capture system, and the clips are transmitted to a distribution system.
Abstract: A media content capture and distribution system includes at least one capture system which provides clips of media content satisfying a set of at least one trigger defined for the capture system. The clips are transmitted to a distribution system. A channel creator in the distribution system combines a plurality of the clips that satisfy at least a portion of the criteria defining the content requirements of a microchannel into a microchannel stream. The microchannel stream is transmitted to a client through a computer network.
TL;DR: The ability to modify the surface charge on specific surfaces within a preformed plastic microchannel allows for fine control, adjustment, and modulation of the electroosmotic flow without using wall coatings or changing the geometry of the channel to achieve the desired flow profile.
Abstract: A pulsed UV excimer laser (KrF, 248 nm) was used to modify the surface charge on the side wall of hot-embossed microchannels fabricated in a poly(methyl methacrylate) substrate. Subablation level fluences, less than 2385 mJ/cm2, were used to prevent any changes in the physical morphology of the surface. It is shown that the electroosmotic mobility, induced by an electric field applied along the length of the channel, increases by an average of 4% in the regions that have been exposed to UV laser pulses compared to nonexposed regions. Furthermore, application of UV modification to electroosmotic flow around a 90° turn results in a decrease in band broadening, as measured by the average decrease in the plate height of 40% compared to flow around a nonmodified turn. The ability to modify the surface charge on specific surfaces within a preformed plastic microchannel allows for fine control, adjustment, and modulation of the electroosmotic flow without using wall coatings or changing the geometry of the chann...
Patent•
01 Aug 2001
TL;DR: In this paper, a combinatorial approach is used to identify optimum catalysts and/or reaction conditions for performing gas-to-liquid reactions in a micro-channel reactor, which can be used directly to optimize large scale reactions performed in a plurality of microchannel reactors.
Abstract: Methods for discovering optimum catalysts and/or reaction conditions for performing endo-or exothermic reactions, in particular gas-to-liquid reactions, are disclosed. A combinatorial approach is used to identify optimum catalysts and/or reaction conditions for performing the reactions. The reactions are performed in the channels of a microchannel reactor. These results can be used directly to optimize large scale reactions performed in a plurality of microchannel reactors, or can be correlated to useful catalysts and reaction conditions for use in large scale reactors by taking into consideration the heat transfer effects in the microchannel reactor and the large scale reactor. The method can advantageously be used to generate a database of combinations of catalyst systems and/or reaction conditions which provide various product streams, such that as market conditions vary and/or product requirements change, conditions suitable for forming desired products can be identified with little or no downtime. The catalysts can be evaluated using varied reaction conditions, which can provide a) a combinatorial library of product streams and a database including the combination of catalysts and reaction conditions to provide each product stream and/or b) the optimum combination of catalysts and reaction conditions for obtaining a desired product stream.
TL;DR: The reproducible synthesis, precise characterization, and excellent DNA sequencing performance of high molar mass, thermoresponsive polymer matrices that exhibit a reversible, temperature-controlled "viscosity switch" that decouples matrix loading and sieving properties, enabling acceleration of microchannel flow by 3 orders of magnitude.
Abstract: Polymers and hydrogels that swell or shrink in response to environmental stimuli such as changes in temperature, pH, or ionic strength are of interest as switchable materials for applications in bi...
TL;DR: A modular approach to fabrication of three-dimensional microchannel systems in polydimethylsiloxane (PDMS) is presented, based on building blocks with microstructuring on up to three faces, which was applied to the fabrication of a 3D-sheath flow microchip.
Abstract: A modular approach to fabrication of three-dimensional microchannel systems in polydimethylsiloxane (PDMS) is presented. It is based on building blocks with microstructuring on up to three faces. The assembled 3D-microchip consists of three building blocks in two layers. For assembly of the bottom layer two building blocks are joined horizontally, whereby the side structuring of the first is sealed against the flat side surface of the other. This results in the formation of a vertical interconnection opening between the building blocks to supplement the microstructuring on the lower faces. The 3D microchannel system is completed by placing a third building block, with microstructuring only on its lower face, on top of the assembled layer. While plasma assisted bonding is used between the two building blocks of the bottom layer, inherent adhesion is sufficient between the layers and for attaching the assembled 3D-microchip to a substrate. This modular approach was applied to
the fabrication of a 3D-sheath flow microchip. It comprises a 20 μm deep microchannel system with sample inlet, open sensing area and outlet in the bottom layer and sheath flow inlet in the top layer. 100 μM fluorescein at 6 μL min−1 was used as sample flow and water at increasing flow rates as sheath flow. With ratios of sheath to sample flow up to 20∶1 sample layers down to 1 μm thickness could be generated. Sample layer thickness was determined via volume detection on an epi-fluorescence microscope followed by image analysis.
TL;DR: In this paper, a polymeric divinylbenzene microspheres (MS) of narrow size distributions were prepared by microchannel emulsification and subsequent polymerization, where the MS diameter can be controlled by the size of the MC.
Abstract: Polymeric divinylbenzene microspheres (MS) of narrow size distributions were prepared by microchannel (MC) emulsification and subsequent polymerization. Using two types of MC plates, large MS with 9.2 μm diameter on average and 5.7% coefficient of variation, as well as small MS with 3.4 μm diameter on average and 7.4% coefficient of variation were prepared. The MS diameter can be controlled by the size of the MC. This method is advantageous for synthesizing polymeric MS of narrow size distributions because of its simplicity.
TL;DR: In this article, the characteristics of electroosmotic flow in a cylindrical microchannel with non-uniform zeta potential were investigated, where the Poisson-Boltzmann equation and momentum equation were used to model the electrical double-layer field and the flow field.
TL;DR: In this paper, the authors describe novel methods for fabricating one component in the complementary metal-oxide-semiconductor (CMOS) microfluidic system, the microchannel.
Abstract: With microfluidic systems becoming more prominent, fabrication techniques for microfluidic systems are increasingly more important. An interesting alternative to existing fabrication techniques is to embed fluidic systems within an integrated circuit by micromachining materials in the integrated circuit itself. This paper describes novel methods for fabricating one component in the complementary metal-oxide-semiconductor (CMOS) microfluidic system, the microchannel. These techniques allow direct integration of sensors, actuators, or other electronics with the microchannel. This method expands the functional applications for microfluidic systems beyond their current abilities. By utilizing the methods described within this paper, a complete "smart" microfluidic system could be batch fabricated on a single integrated circuit (IC) chip.
TL;DR: The integrated microfluidic system proposed here allows multi-ion sensing, which is not easily demonstrated by conventional ion sensor technology using a solvent polymeric membrane, and the required amounts of expensive reagents in one measurement could be reduced.
Abstract: A sequential ion-sensing system using a single microchip was successfully realized. The system developed here involves intermittent pumping of plural organic phases into a microchannel, followed by contact with a single aqueous phase to form a stable organic-aqueous two-layer flow inside the microchannel. Because the plural organic phases created by intermittent flow contain the same lipophilic pH indicator dye but different ion-selective neutral ionophores, different ions can be sequentially and selectively extracted into the different organic phases, where they can be determined by thermal lens microscopy (TLM). We used KD-A3 as the lipophilic pH indicator dye and valinomycin and DD16C5 as neutral ionophores to demonstrate sequential ion sensing of potassium and sodium ions by measuring the deprotonated dye caused by the ion extraction. The integrated microfluidic system proposed here allows multi-ion sensing, which is not easily demonstrated by conventional ion sensor technology using a solvent polymeric membrane. The minimum volume of single organic phase needed to obtain an equilibrium response without dilution by cross dispersion of two organic phases was ca. 500 nL in our system, indicating that the required amounts of expensive reagents in one measurement could be reduced to 1.7 ng and 2.8 ng for the dye and ionophore molecules, respectively.