Transverse imaging and simulation of dsDNA electrophoresis in microfabricated glass channels

We have observed the non-uniform distribution of DNA molecules during PAGE in a microfabricated system. Confocal laser scanning microscopy was used to visualize fluorescently labeled DNA during electrophoretic migration. The distribution of double-stranded DNA larger than 100 bp is observed to transition from a center-biased motion on the transverse plane 1 cm downstream from injection to an edge-biased motion 2 cm downstream. Although this distribution increased with increasing dsDNA size in a cross-linked gel, no similar distribution was found with the same dsDNA molecules in a linear polyacrylamide solution (6%). Simulations of DNA distribution in gels suggest that DNA distribution non-uniformities may be caused by biased electrophoretic migration resulting from motion in an inhomogeneous gel system.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/61440/1/4768_ftp.pd

Mathematical modeling of drop mixing in a slit-type microchannel

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 cm2 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.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/49031/2/jm1516.pd

Self-contained actuation of phase-change pistons in microchannels

An inchworm-like self-contained actuation mechanism for phase-change pistons using a movable thermopneumatic air chamber has been demonstrated. Two phase-change pistons that enclose an air pocket between them have been moved incremental distances by successive melting and solidification of the pistons timed with the expansion and contraction of the air pocket. For a system in which both pistons were wax-based, localized heating of each piston and the air chamber was used to achieve the motion of the assembly. This design used a two-component wax piston that did not coat the microchannel walls. In a separate design a combination of a wax piston with a piston that solidifies at high temperatures was used to eliminate the localized heating requirement for self-contained actuation. This actuation mechanism can be easily integrated on lab-on-a-chip devices for the self-contained pumping of fluid columns.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/49049/2/jmm6_4_015.pd

Surface-modified polyolefin microfluidic devices for liquid handling

Polymer-based microfluidic devices offer an attractive platform for single-use disposable applications due to their low cost, ease of fabrication and good biocompatibility. In this work, we investigated liquid handling in surface modified polyolefin microfluidic devices. The modification of the surface was accomplished using ultraviolet light, and the contact angle was reduced from 88° to 45°. This type of treatment is easy to implement and could be beneficial for liquid handling in microchannel networks. Capillary-driven flow, contact angle hysteresis and pulsed pumping were demonstrated in these plastic devices. This surface treatment also facilitates rapid gel loading for separation since viscous sieving media can be injected solely by capillary force. Nucleic acid separation was demonstrated in the gel-loaded devices.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/49036/2/jmm5_11_023.pd

Recuperative parametric pumping in adsorptive membranes

Recuperative parametric pumping in adsorptive membranes, a cyclical adsorptive separation process, can lead to two distinct mechanisms of separation: rejection and preferential transport. During rejection, the adsorptive membrane rejects an adsorbing solute while permitting the transport of nonadsorbing solutes. During preferential transport the reverse occurs; the adsorptive membrane selectively transports an adsorbing solute while preventing the transport of nonadsorbing solutes. Switching from rejection to preferential transport can be accomplished by merely decreasing the ratio of the stroke volume (cyclical volume of solution pumped into and out of the membrane) to the membrane void volume. Preferential transport, earlier called an “inverse separation,” results from the adsorbing solute crossing over from an adsorbing to a desorbing region in the interior of the membrane and is governed by the shape of the equilibrium isotherms and by process variables. In experiments with lysozyme and a membrane chromatography cartridge, selectivities obtained by preferential transport were on the order of 5 and agreed with theoretical predictions. Theoretical predictions suggest that to further improve separation by preferential transport, experiments need to be conducted on low dispersion membranes (Pe > 10 4 ) and that both rejection and preferential transport can lead to continuous concentrated streams of the adsorbing solutes.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/37437/1/690420111_ftp.pd

Enteric Absorption of Ciprofloxacin During Tube Feeding in the Critically Ill

To determine the pharmacokinetic properties of ciprofloxacin in the critically ill, we studied seven mechanically ventilated patients with pneumonia during entcral feedings. Subjects received ciprofloxacin 750 mg every 12 h via nasogastric tube and serial serum drug concentrations were measured after the first and fourth dose. After the initial dose, the maximum serum concentration ranged from 1.24–3.06 mg/L, and the area under the time curve from 0–12 h ranged from 3.2–19.65 mg.h/L. Similar levels were noted after dose four. Gastrointestinal absorption of ciprofloxacin in tube fed critically ill patients was decreased, but well above MIC values for many pathogenic bacteria

Ecological IVIS design : using EID to develop a novel in-vehicle information system

New in-vehicle information systems (IVIS) are emerging which purport to encourage more environment friendly or ‘green’ driving. Meanwhile, wider concerns about road safety and in-car distractions remain. The ‘Foot-LITE’ project is an effort to balance these issues, aimed at achieving safer and greener driving through real-time driving information, presented via an in-vehicle interface which facilitates the desired behaviours while avoiding negative consequences. One way of achieving this is to use ecological interface design (EID) techniques. This article presents part of the formative human-centred design process for developing the in-car display through a series of rapid prototyping studies comparing EID against conventional interface design principles. We focus primarily on the visual display, although some development of an ecological auditory display is also presented. The results of feedback from potential users as well as subject matter experts are discussed with respect to implications for future interface design in this field

Glance behaviours when using an in-vehicle smart driving aid : a real-world, on-road driving study

In-vehicle information systems (IVIS) are commonplace in modern vehicles, from the initial satellite navigation and in-car infotainment systems, to the more recent driving related Smartphone applications. Investigating how drivers interact with such systems when driving is key to understanding what factors need to be considered in order to minimise distraction and workload issues while maintaining the benefits they provide. This study investigates the glance behaviours of drivers, assessed from video data, when using a smart driving Smartphone application (providing both eco-driving and safety feedback in real-time) in an on-road study over an extended period of time. Findings presented in this paper show that using the in-vehicle smart driving aid during real-world driving resulted in the drivers spending an average of 4.3% of their time looking at the system, at an average of 0.43 s per glance, with no glances of greater than 2 s, and accounting for 11.3% of the total glances made. This allocation of visual resource could be considered to be taken from ‘spare’ glances, defined by this study as to the road, but off-centre. Importantly glances to the mirrors, driving equipment and to the centre of the road did not reduce with the introduction of the IVIS in comparison to a control condition. In conclusion an ergonomically designed in-vehicle smart driving system providing feedback to the driver via an integrated and adaptive interface does not lead to visual distraction, with the task being integrated into normal driving

Heat-transfer analysis of microfabricated thermocapillary pumping and reaction devices

A heat-transfer analysis was performed on thermocapillary pumping, a surface-tension-based drop pumping mechanism. The analysis, which incorporates both fluid flow and energy transport through multiple device layers, reveals effective material, design, and operational choices that result in improved pumping performance. Important design factors include thermal conductivity, channel/substrate thickness, and the velocity of the liquid drops. Results for pumping a drop of water on a fused silica substrate with a glass channel show that uniform interface temperatures can be achieved with bottom heating as long as drop velocities remain below ~0.1 cm s-1 . The analysis was also extended to include thermal reaction channels. The reactor analysis verified that relatively uniform reaction temperatures were attainable with bottom heating as long as channel heights were below ~100 µm.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/49025/2/jm0107.pd