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 “skeletal” biofilm patterns, “hidden” 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 “mushroom” 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 “Microfluidics-Based Microsystem Integration Research” 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 “Spectral Imaging at the Microscale and Beyond” 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-à-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 whole‐cell catalysis is vital for understanding and optimizing bioflow reactors. In this work, we demonstrate the applicability of a flow‐adapted version of Michaelis‐Menten kinetics to an electrocatalytic bacterial biofilm. A three‐electrode microfluidic biofilm flow reactor measured increased turnover rates by as much as 50 % from a Geobacter sulfurreducens biofilm as flow rate was varied. Based on parameters from the applied kinetic framework, flow‐induced 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 well‐studied catalytic systems such as enzymes