49 research outputs found
Linear scanning ATR-FTIR for chemical mapping and high-throughput studies of Pseudomonas sp. biofilms in microfluidic channels
A fully automated linear scanning attenuated total reflection (ATR) accessory
is presented for Fourier transform infrared (FTIR) spectroscopy. The approach
is based on the accurate displacement of a multi-bounce ATR crystal relative to
a stationary infrared beam. To ensure accurate positioning and to provide a
second sample characterization mode, a custom-built microscope was integrated
into the system and the computerized work flow. Custom software includes
automated control and measurement routines with a straightforward user
interface for selecting parameters and monitoring experimental progress. This
cost-effective modular system can be implemented on any research-grade
spectrometer with a standard sample compartment for new bioanalytical chemistry
studies. The system was validated and optimized for use with microfluidic flow
cells containing growing Pseudomonas sp. bacterial biofilms. The
complementarity among the scan positioning accuracy, measurement spatial
resolution and the microchannel dimensions paves the way for parallel
biological assays with real-time control over environmental parameters and
minimal manual labor. By rotating the channel orientation relative to the beam
path, the system could also be used for acquisition of linear biochemical maps
and stitched microscope images along the channel length.Comment: 9 pages, 6 figure
Live-streaming: time-lapse video evidence of novel streamer formation mechanism and varying viscosity
Time-lapse videos of growing biofilms were analyzed using a background subtraction method, which removed camouflaging effects from the heterogeneous field of view to reveal evidence of streamer formation from optically dense biofilm segments. In addition, quantitative measurements of biofilm velocity and optical density, combined with mathematical modeling, demonstrated that streamer formation occurred from mature, high-viscosity biofilms. We propose a streamer formation mechanism by sudden partial detachment, as opposed to continuous elongation as observed in other microfluidic studies. Additionally, streamer formation occurred in straight microchannels, as opposed to serpentine or pseudo-porous channels, as previously reported
One-step fabrication of microchannels with integrated three dimensional features by hot intrusion embossing
We build on the concept of hot intrusion embossing to develop a one-step fabrication
method for thermoplastic microfluidic channels containing integrated three-dimensional features.
This was accomplished with simple, rapid-to-fabricate imprint templates containing microcavities
that locally control the intrusion of heated thermoplastic based on their cross-sectional geometries.
The use of circular, rectangular and triangular cavity geometries was demonstrated for the
purposes of forming posts, multi-focal length microlense arrays, walls, steps, tapered features and
three-dimensional serpentine microchannels. Process variables, such as temperature and pressure,
controlled feature dimensions without affecting the overall microchannel geometry. The approach
was demonstrated for polycarbonate, cycloolefin copolymer and polystyrene, but in principle is
applicable to any thermoplastic. The approach is a step forward towards rapid fabrication of complex,
robust, microfluidic platforms with integrated multi-functional elements
On the nature of âskeletalâ biofilm patterns, âhiddenâ heterogeneity and the role of bubbles to reveal them
Abstract A short communication on the recent paper by Jang et al. discusses the role of âmushroomâ structures and effects of nearly static bubbles on nascent biofilms
Altered biofilm formation at plasma bonded surfaces in microchannels studied by attenuated total reflection infrared spectroscopy
This paper is dedicated to Professor P.R. Norton on the occasion of his 75th birthday, in honor of his profound contributions to Surface Science. In this work, we investigate how plasma bonding of a germanium ATR crystal to a microfluidic device can affect biofilm growth and development. Using attenuated total reflection Fourier transform infrared spectroscopy, individual measurements were made at the attachment surface of growing Pseudomonas fluorescens biofilms in adjacent flow channels during parallel experiments. Biofilm growth in channels with ATR surfaces exposed to air plasma exhibited a faster accumulation of a biomolecular conditioning layer compared to unexposed channels. As well, in-line microscopy revealed enhanced bulk biofilm growth in plasma-treated channels. Since the surface chemistry the Ge ATR was only partially recovered to its original state during the three day experiments, it is believed that the enhanced biofilm growth was ultimately due effects of plasma exposure. It is proposed that observations are transferable to microfluidic devices with sealing layers from other hard surfaces such as glass, silicon and plastic due to their ability to retain surface functionalization after plasma exposure. Plasma treatment could, therefore, offer a route to faster start up times for bioreactors, but could also result in unexpected artifacts in other studies
Recent Advancements towards Full-System Microfluidics
Microfluidics is quickly becoming a key technology in an expanding range of fields, such as medical sciences, biosensing, bioactuation, chemical synthesis, and more. This is helping its transformation from a promising R&D tool to commercially viable technology. Fuelling this expansion is the intensified focus on automation and enhanced functionality through integration of complex electrical control, mechanical properties, in situ sensing and flow control. Here we highlight recent contributions to the Sensors Special Issue series called âMicrofluidics-Based Microsystem Integration Researchâ under the following categories: (i) Device fabrication to support complex functionality; (ii) New methods for flow control and mixing; (iii) Towards routine analysis and point of care applications; (iv) In situ characterization; and (v) Plug and play microfluidics
Spectral Imaging at the Microscale and Beyond
Here we give context to the special issue âSpectral Imaging at the Microscale and Beyondâ in Sensors. We start with an introduction and motivation for the need for spectral imaging and then present important definitions and background concepts. Following this, we review new developments and applications in environmental monitoring, biomaterials, microfluidics, nanomaterials, healthcare, agriculture and food science, with a special focus on the articles published in the special issue. Some concluding remarks put the presented developments in context vis-Ă -vis the future of spectral imaging
A generalized kinetic framework applied to whole-cell bioelectrocatalysis in bioflow reactors clarifies performance enhancements for geobacter sulfurreducens biofilms
A common kinetic framework for studies of wholeâcell catalysis is vital for understanding and optimizing bioflow reactors. In this work, we demonstrate the applicability of a flowâadapted version of MichaelisâMenten kinetics to an electrocatalytic bacterial biofilm. A threeâelectrode microfluidic biofilm flow reactor measured increased turnover rates by as much as 50â% from a Geobacter sulfurreducens biofilm as flow rate was varied. Based on parameters from the applied kinetic framework, flowâinduced increases to turnover rate, catalytic efficiency and device reaction capacity could be linked to an increase in catalytic biomass. This study demonstrates that a standardized kinetic framework is critical for quantitative measurements of new living catalytic systems in flow reactors and for benchmarking against wellâstudied catalytic systems such as enzymes