design-evaluation-smart-glasses-for-food-intake-physical-activity

Design and Evaluation of Smart Glasses for Food Intake and Physical Activity Classification

This study presents a series of protocols of designing and manufacturing a glasses-type wearable device that detects the patterns of temporalis muscle ...

We describe a microfluidic device for generating nonlinear (exponential and sigmoidal) concentration gradients, coupled with a microwell array for cell storage and analysis. The device has two inputs for coflowing multiple aqueous solutions, a main coflow channel and an asymmetrical grid of fluidic channels that allows the two solutions to combine at intersection points without fully mixing. Due to this asymmetry and diffusion of the two species in the coflow channel, varying amounts of the two solutions enter each fluidic path. This induces exponential and sigmoidal concentration gradients at low and high flow rates, respectively, making the microfluidic device versatile. A key feature of this design is that it is space-saving, as it does not require multiplexing or a separate array of mixing channels. Furthermore, the gradient structure can be utilized in concert with cell experiments, to expose cells captured in microwells to various concentrations of soluble factors. We demonstrate the utility of this design to assess the viability of fibroblast cells in response to a range of hydrogen peroxide (H(2)O(2)) concentrations.

Generating nonlinear concentration gradients in microfluidic devices for cell studies.

Wir beschreiben ein mikrofluidische Ger&auml;t zur Erzeugung von nichtlinearen (exponentielle und sigmoiden) Konzentration Steigungen, gekoppelt mit einem Microwell-Array f&uuml;r Zelle Speicherung und Analyse. Das Ger&auml;t verf&uuml;gt &uuml;ber zwei Eing&auml;nge f&uuml;r coflowing mehrere w&auml;ssrige L&ouml;sungen, ein Haupt-Coflow-Kanal und eine asymmetrische Grid fluidische Kan&auml;le, die die beiden L&ouml;sungen an Schnittpunkten zu kombinieren, ohne voll mischen erlaubt. Aufgrund dieser Asymmetrie und die Verbreitung der beiden Arten in der Coflow-Kanal geben Sie unterschiedliche Mengen der beiden L&ouml;sungen jede fluidische Pfad. Dies induziert exponentielle und sigmoiden Konzentration Steigungen bei niedrigen und hohen Flussraten, bzw. machen das mikrofluidische Ger&auml;t vielseitig. Ein wesentliches Merkmal dieses Entwurfs ist, dass es platzsparend, da es keine multiplexing oder ein separates Array Kan&auml;le mischen erfordert. Dar&uuml;ber hinaus kann die gradient-Struktur im Konzert mit Zelle Experimente, in Vertiefungen in unterschiedlichen Konzentrationen l&ouml;sliche Faktoren erfasst Zellen verf&uuml;gbar machen genutzt werden. Wir demonstrieren die N&uuml;tzlichkeit dieses Design zu beurteilen, die Lebensf&auml;higkeit der Fibroblast Zellen als Reaktion auf eine Reihe von Wasserstoffperoxid (H(2)O(2))-Konzentrationen.

Generieren nichtlineare Konzentration Steigungen in Microfluidic Vorrichtungen f&uuml;r Zelle Studien.

This paper presents direct visualization of uptake directionality for cell-membrane impermeant fluorescent molecules and fluorescence-doped nanoparticles at a single-cell level during electroporation. To observe directly the uptake direction, we used microchannel-type electroporation that can generate a relatively symmetric and uniform electric field. For all the image frames during electroporation, fluorescence intensities that occurred at cell membranes in both uptake directions toward the electrodes have been sequentially recorded and quantitatively analyzed pixel by pixel. In our experiments, we found that fluorescent molecules, even not labeled to target biomolecules, had their own uptake direction with different intensities. It is also observed that the uptake intensity toward the cell membrane had a maximal value at a certain electric voltage, not at the highest value of voltages applied. The results also imply that the uptake direction of fluorescence-doped nanoparticles can be determined by a net surface charge of uptake materials and sizes in the electroporative environments. In summary, we performed a quantitative screening and direct visualization of uptake directionality for a set of fluorescent molecules and fluorescence-doped nanoparticles using electric-pulsation. Taking a closer look at the uptake direction of exogenous materials will help researchers to understand an unknown uptake phenomenon in which way foreign materials are inclined to move, and furthermore to design functional nanoparticles for electroporative gene delivery.

Seeing the electroporative uptake of cell-membrane impermeable fluorescent molecules and nanoparticles.

Unwanted sedimentation and attachment of a number of cells onto the bottom channel often occur on relatively large-scale inlets of conventional microfluidic channels as a result of gravity and fluid shear. Phenomena such as sedimentation have become recognized problems that can be overcome by performing microfluidic experiments properly, such as by calculating a meaningful output efficiency with respect to real input. Here, we present a dual-inlet design method for reducing cell loss at the inlet of channels by adding a new " upstream inlet " to a single main inlet design. The simple addition of an upstream inlet can create a vertically layered sheath flow prior to the main inlet for cell loading. The bottom layer flow plays a critical role in preventing the cells from attaching to the bottom of the channel entrance, resulting in a low possibility of cell sedimentation at the main channel entrance. To provide proof-of-concept validation, we applied our design to a microfabricated flow cytometer system (μFCS) and compared the cell counting efficiency of the proposed μFCS with that of the previous single-inlet μFCS and conventional FCS. We used human white blood cells and fluorescent microspheres to quantitatively evaluate the rate of cell sedimentation in the main inlet and to measure fluorescence sensitivity at the detection zone of the flow cytometer microchip. Generating a sheath flow as the bottom layer was meaningfully used to reduce the depth of field as well as the relative deviation of targets in the z-direction (compared to the x-y flow plane), leading to an increased counting sensitivity of fluorescent detection signals. Counting results using fluorescent microspheres showed both a 40% reduction in the rate of sedimentation and a 2-fold higher sensitivity in comparison with the single-inlet μFCS. The results of CD4(+) T-cell counting also showed that the proposed design results in a 25% decrease in the rate of cell sedimentation and a 28% increase in sensitivity when compared to the single-inlet μFCS. This method is simple and easy to use in design, yet requires no additional time or cost in fabrication. Furthermore, we expect that this approach could potentially be helpful for calculating exact cell loading and counting efficiency for a small input number of cells, such as primary cells and rare cells, in microfluidic channel applications.

Effect of a dual inlet channel on cell loading in microfluidics.

Fluorescence cell imaging using a fluorescence microscope is an extensively used technique to examine the cell nucleus, internal structures, and other cellular molecules with fluorescence response time and intensity. However, it is difficult to perform high resolution cell imaging for a long period of time with this technique due to necrosis and apoptosis depending on the type and subcellular location of the damage caused by phototoxicity. A large number of studies have been performed to resolve this problem, but researchers have struggled to meet the challenge between cellular viability and image resolution. In this study, we employ a specially designed disc to reduce cell damage by controlling total fluorescence exposure time without deterioration of the image resolution. This approach has many advantages such as, the apparatus is simple, cost-effective, and easily integrated into the optical pathway through a conventional fluorescence microscope.

Spirally-patterned pinhole arrays for long-term fluorescence cell imaging.

Nafion has received great attention as a proton conductor that can block negative ions. Here, we report the effect of a Nafion coating on an anodic aluminium oxide (AAO) nanoporous membrane on its function of ion rejection and filtering depending on the electric field. In our experiments, Nafion, once coated, was used to repel the negative ions (anions) from the coated surface, and then selectively allowed positive ions (cations) to pass through the nanopores in the presence of an electric field. To demonstrate the proof-of-concept validation, we coated Nafion solution onto the surface of AAO membranes with 20 nm nanopores average diameter at different solution concentration levels. Vacuum filtration methods for Nafion coating were vertically applied to the plane of an AAO membrane. An electric field was then applied to the upper surface of the Nafion-coated AAO membrane to investigate if ion rejection and filtering was affected by the presence of the electric field. Both anions and cations could pass through the AAO nanopores without an electric field applied. However, only cations could well pass through the AAO nanopores under an electric field, thus effectively blocking anions from passing through the nanopores. This result shows that ion filtration of electrons has been selectively performed while the system also works as a vital catalyst in reactivating Nafion via electrolysis. A saturated viscosity ratio of Nafion solution for the coating was also determined. We believe that this approach is potentially beneficial for better understanding the fundamentals of selective ion filtration in nanostructures and for promoting the use of nanostructures in potential applications such as ion-based water purification and desalination system at the nanoscale in a massively electrically integrated format.

Role of the electric field in selective ion filtration in nanostructures.

In this study, we present a role of arrayed micropillar structures in cell rolling dynamics. Cell rolling on a ligand coated surface as a means of cell separation was demonstrated using a micropillar-integrated microfluidic channel. This approach allows the separation of cells according to characteristic surface properties, regardless of cell size. In these experiments, different moving trajectories of the cells between a ligand-coated micropost structure and a 1% BSA coated micropost structure were observed using sequential images. Based on the analysis of the angle of travel of cells in the trajectory, the average angles of travel on the ligand-coated microposts were 1.5° and -3.1° on a 1% BSA-coated micropost structure. The overall force equivalent applied to a cell can be analyzed to predict the cell rolling dynamics when a cell is detached. These results show that it will be possible to design chip geometry for delicate operations and to separate target cells. Furthermore, we believe that these control techniques based on a ligand coated micropillar surface can be used for enhancing cell rolling-based separation in a faster and more continuous manner.

Role of micropillar arrays in cell rolling dynamics.

Here we present a new method for automatic and objective monitoring of ingestive behaviors in comparison with other facial activities through load cells embedded in a pair of glasses, named GlasSense. Typically, activated by subtle contraction and relaxation of a temporalis muscle, there is a cyclic movement of the temporomandibular joint during mastication. However, such muscular signals are, in general, too weak to sense without amplification or an electromyographic analysis. To detect these oscillatory facial signals without any use of obtrusive device, we incorporated a load cell into each hinge which was used as a lever mechanism on both sides of the glasses. Thus, the signal measured at the load cells can detect the force amplified mechanically by the hinge. We demonstrated a proof-of-concept validation of the amplification by differentiating the force signals between the hinge and the temple. A pattern recognition was applied to extract statistical features and classify featured behavioral patterns, such as natural head movement, chewing, talking, and wink. The overall results showed that the average F1 score of the classification was about 94.0% and the accuracy above 89%. We believe this approach will be helpful for designing a non-intrusive and un-obtrusive eyewear-based ingestive behavior monitoring system.

A glasses-type wearable device for monitoring the patterns of food intake and facial activity.

Most conventional methods for assessing uptake of exogenous molecules and nanomaterials into cells use the projected two-dimensional (2D) area of uptake intensity into individual cells. However, since most cells have a three-dimensional (3D) spherical shape, volumetric uptake cannot be quantified accurately using 2D area analysis. Here, we present a method for calibrating the electroporative uptake intensity of small molecules by using a novel predictable spherical volume (PSV) model, which is more accurate and quantitative than previous methods. As a proof-of-concept, we visualized the electroporative uptake of propidium iodide (PI) into mammalian cells in a single rectangular polydimethylsiloxane (PDMS) microfluidic channel, often used for direct observation of on-chip cell electroporation. Our PSV method yielded more accurate results than conventional methods and faithfully reflected volumetric changes in uptake intensity, even those due to microflow. We believe that this approach can be potentially beneficial for screening the electroporative uptake efficiency of cell-membrane impermeable nanodrugs, such as functional nanoparticles incorporated with a small drug capable of slowly diffusing inside cells.

Calibration of on-chip cell electroporation by a pseudo-volumetric uptake model.

A protocol for quantitative image analysis of wound generation is important to better understand the integrative process of wound healing and the closure mechanism. Here, we present a method for quantitative analysis of microscopic images of circular wound sites generated by vertically stamped scratches. To demonstrate proof-of-concept validation, we used two types of mechanical stamping tools, a mechanical pencil lead (type 1; brittle) and polydimethylsiloxane (PDMS) pillars (type 2; ductile), to create circular wound sites. We also present a method for analysis of microscopic images of the generated wound sites by suggesting new parameters, such as controlled area transfer ratio, modified shape factor, and roundness index, specifically to investigate the shape and size of wounds via house-coded image processing. We believe that this approach can be potentially useful by providing a better way of studying vertical wound generation for future skin wound generation and care applications compared with its counterpart, conventional horizontal wound generation.

Article	Year
Generating nonlinear concentration gradients in microfluidic devices for cell studies. Analytical chemistry\| PubMed ID: 21344866	2011
Seeing the electroporative uptake of cell-membrane impermeable fluorescent molecules and nanoparticles. Nanoscale\| PubMed ID: 22767182	2012
Effect of a dual inlet channel on cell loading in microfluidics. Biomicrofluidics\| PubMed ID: 25553201	2014
Spirally-patterned pinhole arrays for long-term fluorescence cell imaging. The Analyst\| PubMed ID: 26381726	2015
Role of the electric field in selective ion filtration in nanostructures. The Analyst\| PubMed ID: 26813413	2016
Role of micropillar arrays in cell rolling dynamics. The Analyst\| PubMed ID: 27827471	2016
A glasses-type wearable device for monitoring the patterns of food intake and facial activity. Scientific reports\| PubMed ID: 28134303	2017
Calibration of on-chip cell electroporation by a pseudo-volumetric uptake model. Micron (Oxford, England : 1993)\| PubMed ID: 28414960	2017
Quantitative image analysis of the shape and size of circular wound sites generated by vertically stamped scratches. Micron (Oxford, England : 1993)\| PubMed ID: 28628808	2017

Won Gu Lee

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