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Critique an article
Digital microfluidics
 * 1) Is each fact referenced with an appropriate, reliable reference?  For the entire article only three references are cited, with two of the sources solely for citing "Electrowetting On Dielectric." The other source is only cited twice, once to contrast it with continuous-flow microfluidics, and the other for the first investigation of digital microfluidics by Cytonix. All three references look to be reliable sources, but they are used in such a limited manner that virtually all of the material in the article is not cited.
 * 2) Check a few citations. Do the links work? Is there any close paraphrasing or plagiarism in the article?  Of the three citations two contain links, but both of these cite textbooks. I cannot comment on paraphrasing or plagiarism because of this. In conjunction with the previous comment, much more work needs to be done in regards to the citations.

Add to an article
Digital microfluidics - Separation & Extraction

Digital microfluidics has been used for the extraction of proteins from complex samples.[1] Magnetic particles are used to specifically interact with the protein and the digital microfluidics is used to add, remove, or wash the protein and particle mixture by moving liquid droplets around the surface of the microfluidic device.[1]

1. Seale, B.; Lam, C.; Rackus, D. G.; Chamberlain, M. D.; Liu, C.; Wheeler, A. R. Digital Microfluidics for Immunoprecipitation. Anal. Chem. 2016, 88 (20), 10223–10230.

My Article Before Peer Review
Digital microfluidics can be used for separation and extraction of target analytes by applying other separation techniques on the microfluidic scale. These methods include the use of magnetic particles1–8, liquid-liquid extraction9, optical tweezers10, and hydrodynamic effects11. The use of magnetic particles is well-established and rely on similar principles. A droplet of solution containing the analyte of interest is placed on a DMF electrode array and manipulated by the electrodes. The droplet is moved to an electrode with a magnet on one side of the array with magnetic particles functionalized to bind to the analyte. The droplet is moved over the electrode, the magnetic field is removed and the particles are suspended in the droplet. The droplet is swirled on the electrode array to ensure mixing. The magnet is reintroduced and the particles are immobilized and the droplet is moved away. This process is repeated with wash and elution buffers to extract the analyte.1–8

Seale et al. used magnetic particles coated with antihuman serum albumin antibodies to isolate human serum albumin, as proof of concept work for immunoprecipitation using digital microfluidics.5 DNA extraction from a whole blood sample has also been performed with digital microfluidics, by Hung et al.3 The procedure follows the general methodology described above, but includes pre-treatment on the digital microfluidic platform to lyse the cells prior to DNA extraction.3

Biological separations, which usually involve low concentration, high volume samples, but this can pose an issue for digital microfluidics due to the small sample volume necessary.4 Jebrail et al. have developed a digital microfluidic system that combines with a macrofluidic system designed to decrease sample volume, in turn increasing analyte concentration.4 It follows the same principles as above, but includes pumping of the droplet to cycle a larger volume of fluid around the magnetic particles.4

Wijethunga et al. have used liquid-liquid extraction on a digital microfluidic device by taking advantage of immiscible liquids.9 Two droplets, one containing the analyte in aqueous phase and the other an immiscible ionic liquid. The two droplets are mixed and the ionic liquid extracts the analyte, and the droplets are easily separable.9

Shah et al. have used optical tweezers to separate cells in droplets.10 Two droplets are mixed on an electrode array, one containing the cells and the other with nutrients or drugs. The droplets are mixed and then optical tweezers are used to move the cells to one side of the larger droplet before it is split.10

Particles have been applied for use outside of magnetic separation, Nejad et al. have shown that hydrodynamic forces can be used to separate particles from the bulk of droplet.11 Electrode arrays were designed as a circle with a central electrode (of varying shape) and ‘slices’ of electrodes surrounding it. Droplets are added onto the array and swirled in a circular pattern. The hydrodynamic forces from the swirling cause the particles to aggregate onto the center electrode.11

Extraction of drug analytes from dried urine samples has been shown by Kirby et al.12 A droplet of extraction solvent, in this case methanol, is repeatedly flowed over a sample of dried urine sample then moved to a final electrode where the liquid is extracted through a capillary and then analyzed using mass spectrometry.12

My Article After Peer Review
Digital microfluidics can be used for separation and extraction of target analytes. These methods include the use of magnetic particles1–8, liquid-liquid extraction9, optical tweezers10, and hydrodynamic effects 11. For magnetic particle separations a droplet of solution containing the analyte of interest is placed on a digital microfluidics electrode array and moved by the changes in the charges of the electrodes. The droplet is moved to an electrode with a magnet on one side of the array with magnetic particles functionalized to bind to the analyte. Then it is moved over the electrode, the magnetic field is removed and the particles are suspended in the droplet. The droplet is swirled on the electrode array to ensure mixing. The magnet is reintroduced and the particles are immobilized and the droplet is moved away. This process is repeated with wash and elution buffers to extract the analyte.1–8

Magnetic particles coated with antihuman serum albumin antibodies have been used to isolate human serum albumin, as proof of concept work for immunoprecipitation using digital microfluidics.5 DNA extraction from a whole blood sample has also been performed with digital microfluidics.3 The procedure follows the general methodology  as the magnetic particles, but includes pre-treatment on the digital microfluidic platform to lyse the cells prior to DNA extraction.3

Biological separations usually involve low concentration high volume samples. This can pose an issue for digital microfluidics due to the small sample volume necessary.4 Digital microfluidic systems can be combined with a macrofluidic system designed to decrease sample volume, in turn increasing analyte concentration.4 It follows the same principles as  the magnetic particles for separation, but includes pumping of the droplet to cycle a larger volume of fluid around the magnetic particles.4

Liquid-liquid extractions can be carried out on digital microfluidic device by taking advantage of immiscible liquids.9 Two droplets, one containing the analyte in aqueous phase, and the other an immiscible ionic liquid. The two droplets are mixed and the ionic liquid extracts the analyte, and the droplets are easily separable.9

Optical tweezers to separate cells in droplets.10 Two droplets are mixed on an electrode array, one containing the cells, and the other with nutrients or drugs. The droplets are mixed and then optical tweezers are used to move the cells to one side of the larger droplet before it is split.10

Particles have been applied for use outside of magnetic separation, with hydrodynamic forces to separate particles from the bulk of a droplet.11 This is performed on electrode arrays with a central electrode and ‘slices’ of electrodes surrounding it. Droplets are added onto the array and swirled in a circular pattern, and the hydrodynamic forces from the swirling cause the particles to aggregate onto the central electrode.11

Extraction of drug analytes from dried urine samples has also been reported.12 A droplet of extraction solvent, in this case methanol, is repeatedly flowed over a sample of dried urine sample then moved to a final electrode where the liquid is extracted through a capillary and then analyzed using mass spectrometry.12

Separation and Extraction
Digital microfluidics can be used for separation and extraction of target analytes. These methods include the use of magnetic particles      , liquid-liquid extraction , optical tweezers , and hydrodynamic effects.

Magnetic Particles
For magnetic particle separations a droplet of solution containing the analyte of interest is placed on a digital microfluidics electrode array and moved by the changes in the charges of the electrodes. The droplet is moved to an electrode with a magnet on one side of the array with magnetic particles functionalized to bind to the analyte. Then it is moved over the electrode, the magnetic field is removed and the particles are suspended in the droplet. The droplet is swirled on the electrode array to ensure mixing. The magnet is reintroduced and the particles are immobilized and the droplet is moved away. This process is repeated with wash and elution buffers to extract the analyte.

Magnetic particles coated with antihuman serum albumin antibodies have been used to isolate human serum albumin, as proof of concept work for immunoprecipitation using digital microfluidics.5 DNA extraction from a whole blood sample has also been performed with digital microfluidics.3 The procedure follows the general methodology  as the magnetic particles, but includes pre-treatment on the digital microfluidic platform to lyse the cells prior to DNA extraction.

Liquid-liquid Extraction
Liquid-liquid extractions can be carried out on digital microfluidic device by taking advantage of immiscible liquids.9 Two droplets, one containing the analyte in aqueous phase, and the other an immiscible ionic liquid are present on the electrode array. The two droplets are mixed and the ionic liquid extracts the analyte, and the droplets are easily separable.

Optical Tweezers
Optical tweezers have also been used to separate cells in droplets.10 Two droplets are mixed on an electrode array, one containing the cells, and the other with nutrients or drugs. The droplets are mixed and then optical tweezers are used to move the cells to one side of the larger droplet before it is split.

Hydrodynamic Separation
Particles have been applied for use outside of magnetic separation, with hydrodynamic forces to separate particles from the bulk of a droplet. This is performed on electrode arrays with a central electrode and ‘slices’ of electrodes surrounding it. Droplets are added onto the array and swirled in a circular pattern, and the hydrodynamic forces from the swirling cause the particles to aggregate onto the central electrode.

Biological Extraction
Biological separations usually involve low concentration high volume samples. This can pose an issue for digital microfluidics due to the small sample volume necessary. Digital microfluidic systems can be combined with a macrofluidic system designed to decrease sample volume, in turn increasing analyte concentration. It follows the same principles as  the magnetic particles for separation, but includes pumping of the droplet to cycle a larger volume of fluid around the magnetic particles. Extraction of drug analytes from dried urine samples has also been reported. A droplet of extraction solvent, in this case methanol, is repeatedly flowed over a sample of dried urine sample then moved to a final electrode where the liquid is extracted through a capillary and then analyzed using mass spectrometry.

Reflective Essay
1.     I wrote the article “Digital Microfluidics – Extraction and Separation.” This is not an entirely new article because digital microfluidics existed already, but the section on extraction and separation is new to Wikipedia.

2.     Main Contributions

·       The use magnetic nanoparticles is a major focus of the article due to the large number of publications that use this extraction technique. Different groups across the world have used magnetic nanoparticles in a variety of ways to extract different analytes from solutions.

·       Included in the article are other, less common methods of extraction that take advantage of optical tweezers to isolate analytes in one section of a droplet, hydrodynamic forces to trap analytes on a central electrode using a swirling motion, and liquid-liquid extraction with immiscible aqueous and ionic liquid solutions.

·       Application focused work is also discussed. Extraction of analytes from dried urine samples and a method to increase the concentration of target analytes (by reducing solution volume) are both included in the article.

3.     Response to Reviewers

·       Initially I had cited the authors in text with the format of “Smith et al.” Both reviewers noted that this is not commonplace on Wikipedia, so they were removed and only numeric in text citations were used.

·       Edits to sentence flow and word choice to make the article more readable. For example, changing “Biological separations, which usually involve low concentration, high volume samples, but this can pose an issue for digital microfluidics due to the small sample volume necessary,” to “Biological separations, which usually involve low concentration, high volume samples. This can pose an issue for digital microfluidics due to the small sample volume necessary.”

·       Removal of redundant wordage. For example, removing the underlined portion from the sentence, “Digital microfluidics (DMF) can be used for separation and extraction of target analytes by applying other separation techniques on the microfluidic scale,” and adding more specific information in a following sentence.

·       I did not use the Wikipedia content expert, but feedback was received from an individual outside of the course.

4.     Overall I found the Wikipedia assignment to be a useful twist on the standard end of term paper for two reasons, expansion of Wikipedia and writing for a lay audience. When I come across a new topic when reading publications (or anything else) the first place I go for information is Wikipedia, but for many topics in the sciences (especially relatively new ones) the Wikipedia articles are short or do not exist. This assignment is beneficial to Wikipedia because we are expanding the number of scientific articles present. Now Wikipedia readers will have more direct access to accurate information about microfluidics, and I believe they will be read even more frequently as the field of microfluidics grows.

Since the articles are on Wikipedia it was also important to write them for a lay audience. This is generally a difficult task for science majors, so I think forcing students to alter their audience is an invaluable experience, especially for students who may not be staying in academia. But I do think the assignment could be improved to make it more relevant to other aspects of a term paper. Wikipedia articles are generally short, which I think is detrimental to this assignment. Term papers are usually significantly longer and allow for students to fully explore a topic, and I think this was not present for the Wikipedia assignment. This prevented me from having to really dig into current publications because each one is only relevant for at most a few sentences on the Wikipedia article. Also the peer review process was not that helpful for the article or me as a writer, but this could have been an individual issue. My suggestion to fix these issues would be to assign the Wikipedia assignment in addition to a longer term paper. It would require students to explore their topics more in-depth, while also resulting in publishable Wikipedia articles at the end. With the rest workload of the course I would not consider this to be too much for graduate or undergraduate students.