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Christian Fobel

Bio: Christian Fobel is an academic researcher from University of Toronto. The author has contributed to research in topics: Digital microfluidics & Measles. The author has an hindex of 4, co-authored 5 publications receiving 308 citations.

Papers
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Journal ArticleDOI
TL;DR: DropBot as mentioned in this paper is an open-source instrument for digital microfluidics that can be used for real-time monitoring of instantaneous drop velocity and application of constant electrostatic driving forces through compensation for amplifier-loading and device capacitance.
Abstract: We introduce DropBot: an open-source instrument for digital microfluidics (http://microfluidics.utoronto.ca/dropbot). DropBot features two key functionalities for digital microfluidics: (1) real-time monitoring of instantaneous drop velocity (which we propose is a proxy for resistive forces), and (2) application of constant electrostatic driving forces through compensation for amplifier-loading and device capacitance. We anticipate that this system will enhance insight into failure modes and lead to new strategies for improved device reliability, and will be useful for the growing number of users who are adopting digital microfluidics for automated, miniaturized laboratory operation.

179 citations

Journal ArticleDOI
TL;DR: A compact and portable, field-deployable, point-of-care system relying on digital microfluidics that can rapidly test a small volume of capillary blood for disease-specific antibodies for measles and rubella is described.
Abstract: Serosurveys are useful for assessing population susceptibility to vaccine-preventable disease outbreaks. Although at-risk populations in remote areas could benefit from this type of information, they face several logistical barriers to implementation, such as lack of access to centralized laboratories, cold storage, and transport of samples. We describe a potential solution: a compact and portable, field-deployable, point-of-care system relying on digital microfluidics that can rapidly test a small volume of capillary blood for disease-specific antibodies. This system uses inexpensive, inkjet-printed digital microfluidic cartridges together with an integrated instrument to perform enzyme-linked immunosorbent assays (ELISAs). We performed a field validation of the system’s analytical performance at Kakuma refugee camp, a remote setting in northwestern Kenya, where we tested children aged 9 to 59 months and caregivers for measles and rubella immunoglobulin G (IgG). The IgG assays were determined to have sensitivities of 86% [95% confidence interval (CI), 79 to 91% (measles)] and 81% [95% CI, 73 to 88% (rubella)] and specificities of 80% [95% CI, 49 to 94% (measles)] and 91% [95% CI, 76 to 97% (rubella)] (measles, n = 140; rubella, n = 135) compared with reference tests (measles IgG and rubella IgG ELISAs from Siemens Enzygnost) conducted in a centralized laboratory. These results demonstrate a potential role for this point-of-care system in global serological surveillance, particularly in remote areas with limited access to centralized laboratories.

112 citations

Journal ArticleDOI
TL;DR: It is proposed that this sentiment is a powerful motivation for the "open-source" movement in scientific research, in which creators provide everything needed to replicate a given project online, as well as providing explicit permission for users to use, improve, and share it with others.
Abstract: Isaac Newton famously observed that “if I have seen further it is by standing on the shoulders of giants.” We propose that this sentiment is a powerful motivation for the “open-source” movement in scientific research, in which creators provide everything needed to replicate a given project online, as well as providing explicit permission for users to use, improve, and share it with others. Here, we write to introduce analytical chemists who are new to the open-source movement to best practices and concepts in this area and to survey the state of open-source research in analytical chemistry. We conclude by considering two examples of open-source projects from our own research group, with the hope that a description of the process, motivations, and results will provide a convincing argument about the benefits that this movement brings to both creators and users.

70 citations

Journal ArticleDOI
TL;DR: An automated method to facilitate in-line coupling of digital microfluidics (DMF) with HPLC-MS is introduced, using a custom, 3D-printed manifold and a custom plugin to the popular open-source control system, DropBot.
Abstract: We introduce an automated method to facilitate in-line coupling of digital microfluidics (DMF) with HPLC-MS, using a custom, 3D-printed manifold and a custom plugin to the popular open-source control system, DropBot. The method was designed to interface directly with commercial autosamplers (with no prior modification), suggesting that it will be widely accessible for end-users. The system was demonstrated to be compatible with samples dissolved in aqueous buffers and neat methanol and was validated by application to a common steroid-labeling derivatization reaction. We propose that the methods described here will be useful for a wide range of applications, combining the automated sample processing power of DMF with the resolving and analytical capacity of HPLC-MS.

20 citations

Patent
17 Aug 2017
TL;DR: In this article, a multi-droplet sensing and actuation system for digital microfluidic chip operation is described, where a linearly independent alternating current signal is applied to each discrete actuation electrode thus encoding the electrode's identity.
Abstract: The present disclosure discloses a multi-droplet sensing and actuation system, for use in a digital microfluidic chip operation wherein a linearly independent alternating current signal is applied to each discrete actuation electrode thus encoding the electrode's identity. The combined measured impedance signal from multiple channels is then processed to decode an impedance measurement for the volume between each discrete actuation electrode and its corresponding conductive counter electrode region, where the sensed impedance is inversely proportional to an amount of liquid within the volume.

4 citations


Cited by
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Journal ArticleDOI
TL;DR: This review provides easy-to-understand examples and targets the microtechnology/engineering community as well as researchers in the life sciences, and discusses both research and commercial activities.

375 citations

Journal ArticleDOI
TL;DR: The most recent advances in the DMF platforms are discussed, and the feasibility of developing multifunctional packages for performing complete sets of processes of biochemical assays, particularly for point-of-care applications is evaluated.
Abstract: Following the development of microfluidic systems, there has been a high tendency towards developing lab-on-a-chip devices for biochemical applications. A great deal of effort has been devoted to improve and advance these devices with the goal of performing complete sets of biochemical assays on the device and possibly developing portable platforms for point of care applications. Among the different microfluidic systems used for such a purpose, digital microfluidics (DMF) shows high flexibility and capability of performing multiplex and parallel biochemical operations, and hence, has been considered as a suitable candidate for lab-on-a-chip applications. In this review, we discuss the most recent advances in the DMF platforms, and evaluate the feasibility of developing multifunctional packages for performing complete sets of processes of biochemical assays, particularly for point-of-care applications. The progress in the development of DMF systems is reviewed from eight different aspects, including device fabrication, basic fluidic operations, automation, manipulation of biological samples, advanced operations, detection, biological applications, and finally, packaging and portability of the DMF devices. Success in developing the lab-on-a-chip DMF devices will be concluded based on the advances achieved in each of these aspects.

337 citations

Journal ArticleDOI
TL;DR: The basic concepts and recent histories of electrochemistry, biosensors, and microfluidics are introduced, and how they are combining to form new application-areas, including so-called "point-of-care" systems in which measurements traditionally performed in a laboratory are moved into the field.
Abstract: Electrochemistry, biosensors and microfluidics are popular research topics that have attracted widespread attention from chemists, biologists, physicists, and engineers. Here, we introduce the basic concepts and recent histories of electrochemistry, biosensors, and microfluidics, and describe how they are combining to form new application-areas, including so-called “point-of-care” systems in which measurements traditionally performed in a laboratory are moved into the field. We propose that this review can serve both as a useful starting-point for researchers who are new to these topics, as well as being a compendium of the current state-of-the art for experts in these evolving areas.

274 citations

Journal ArticleDOI
TL;DR: Nonsusceptibility to first-line antibiotics is associated with decreased survival in GNBSIs and DTR is a simple bedside prognostic measure of treatment-limiting coresistance.
Abstract: Background Resistance to all first-line antibiotics necessitates the use of less effective or more toxic “reserve” agents Gram-negative bloodstream infections (GNBSIs) harboring such difficult-to-treat resistance (DTR) may have higher mortality than phenotypes that allow for ≥1 active first-line antibiotic

269 citations

Journal ArticleDOI
TL;DR: The UWED is simple, small in size, assembled from inexpensive components, and completely wireless, it offers new opportunities for the development of affordable diagnostics, sensors, and wearable devices.
Abstract: This paper describes the design and characterization of an open-source “universal wireless electrochemical detector” (UWED). This detector interfaces with a smartphone (or a tablet) using “Bluetooth Low Energy” protocol; the smartphone provides (i) a user interface for receiving the experimental parameters from the user and visualizing the result in real time, and (ii) a proxy for storing, processing, and transmitting the data and experimental protocols. This approach simplifies the design, and decreases both the size and the cost of the hardware; it also makes the UWED adaptable to different types of analyses by simple modification of the software. The UWED can perform the most common electroanalytical techniques of potentiometry, chronoamperometry, cyclic voltammetry, and square wave voltammetry, with results closely comparable to benchtop commercial potentiostats. Although the operating ranges of electrical current and voltage of the UWED (±1.5 V, ±180 μA) are more limited than most benchtop commercial...

238 citations