User:Bzercher/sandbox

Article evaluation https://en.wikipedia.org/wiki/Ion-mobility_spectrometry-mass_spectrometry Reflection paragraph: The article is neutral. There is no postulation that IM-MS is the best mass spectrometry technique, nor does it embellish the history of the technique. However, there are some technical errors. The author uses QMS without initially spelling out the abbreviation. The author also does not cite a source for the development of the Synapt mass spectrometer. In the history section, there is a 25 year gap without any mention of technological development. I also found the description of the technique to be a bit vague.

Text I posted on the article’s talk page:

Were there no significant developments of IMS-MS technology from the 1970s to the late 1990s?

Add to an article

Recently, gas-phase ion activation methods have been used to gain new insights into complex structures. Collision induced unfolding (CIU) is a technique in which an ion's internal energy is increased through collisions with a buffer gas prior to IM-MS analysis. Unfolding of the ion is observed through larger CCSs, and the energy at which unfolding occurs corresponds partially to noncovalent interactions within the ion. This technique has been used to differentiate polyubiquitin linkages and intact antibodies.

Initial planning for my article

Droplet manipulation: fusion and reagent addition

-Introductory sentence about importance of control of reagent addition for concentration, volume, and d=0 To best take advantage of droplet-based microfluidics capabilities for synthetic and biochemical applications, reagent addition must be a robust process that controls for contamination and volume changes. --advantages of droplet-based microfluidics is the segmentation and control of individual droplets to manipulate and monitor reactions -keep “test tube” integrity -diferent approaches have been developed each with advantages and disadvantages

-Laminar flow into the same droplet, then subsequently mixed a la Song Due to the properties of laminar flow in small diameter flow paths, reagents can be combined upon droplet formation by co-flowing two reagent streams into the carrier phase, mixing reagents upon droplet formation. http://onlinelibrary.wiley.com/doi/10.1002/anie.200390203/abstract In this setup, the reagent streams are often separated by a reagent-free solvent stream free to limit contamination by diffusion. Co-flow reagent addition is limited by a lack of flexibility in droplet manipulation possibilities prior to reaction start time.

-Droplet Fusion

-T junction https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1766323/

-Picoinjection http://www.pnas.org/content/107/45/19163.short

-K-Channel combinations http://pubs.acs.org/doi/full/10.1021/acs.analchem.6b05041

Article I emailed for peer review

Droplet manipulation: fusion and reagent addition

Reagent addition is an important but challenging step for droplet-based microfluidic systems. To ensure robustness of high throughput synthetic and biochemical assays, the reagent addition process requires reproducibility at high rates. This has been approached in various ways.

Reagent Co-Flow An early approach for reagent addition utilized a “co-flow” geometry which mixed streams of reactants at the point of droplet formation.1 Reagent streams are pumped in separate channels until they join near the continuous phase and are sheared into droplets that contain both reagents. By different the flow rates in reagent channels, reagent ratios can be controlled. Co-flow reagent addition is limited by a lack of flexibility in droplet manipulation possibilities prior to reaction start time.

Droplet Fusion The fusion of droplets can also be exploited for reagent addition. To accomplish this reproducibly in surfactant-stabilized emulsions, one strategy termed electro-coalescence was developed. This technique merges pairs of droplets by applying an electric field to temporary destabilize the droplets.2,3 A difficulty of electro-coalescence is the need for droplets to come in contact with one another, and then overcome surfactant stabilization. By manipulating droplet size in separate streams, differential flow of droplet sizes can bring droplets into contact before merging by electric field destabilization.3

Injection Methods

To separate reagent addition from droplet creation and fusion methods, a T-junction setup can be utilized.4,5 Reagent is flowed through a channel perpendicular to the droplet stream. An injection droplet is then merged with plug as it passed the channel. Reagent volume is controlled by the flow rate of the side channel. Successful merging of reagent droplets is achieved through customization of side-channel materials. A disadvantage of this T-Junction system is that it does not work for stable emulsions.6

-Picoinjection Adapting the use of the actuated electric field, Abate et. al. achieved sub-picoliter control of reagent injection.6 Their approach, termed picoinjection, utilizes a T-junction reagent delivery channel positioned near two electrodes. As droplets passes the T-junction, the combination of pressurized reagent stream and electrode actuation injected reagents into droplets. By controlling reagent stream pressure and droplet velocity, injection volume can be controlled. This approach is limited by pressure fluctuations throughout the duration of system operation.7

The main drawback of picoinjection is contamination as contents of the droplet may flow out into the reagent channel upon injection, potentially contaminating later droplets. To combat this, Doonan et. al. developed a multifunctional K-channel, which flows reagent streams opposite the path of the droplet stream.8 Utilizing an interface between the two channels, injection is achieved similarly to picoinjection, but any bilateral contamination is washed away through continuous reagent flow. Contamination is avoided at the expense of potentially wasting precious reagent.

Revised article after peer review

Droplet manipulation: fusion and reagent addition Microscale reactions performed in droplet-based applications conserve reagents and reduce reaction time all at very high throughput. Reagent addition to droplet microreactors has been a focus of research due to the difficulty of achieving reproducible additions at kilohertz rates without droplet-to-droplet contamination.

Reagent co-flow and droplet fusion Reagents can be added at the time of droplet formation through a “co-flow” geometry. Reagent streams are pumped in separate channels and join at the interface with a channel containing the continuous phase, which shears and separates droplets containing both reagents. By changing the flow rates in reagent channels, reagent ratios within a droplet can be controlled. The fusion of droplets with different contents can also be exploited for reagent addition. Electro-coalescence merges pairs of droplets by applying an electric field to temporarily destabilize the droplet-droplet interface to achieve reproducibility in surfactant-stabilized emulsions. Electro-coalescence requires droplets (which are normally separated by the continuous phase) to come into contact. By manipulating droplet size in separate streams, differential flow of droplet sizes can bring droplets into contact before merging.

Injection methods Previously described reagent addition methods are tied to droplet formation events which lack downstream flexibility. To decouple reagent addition from droplet creation, a T-junction setup has been utilized. A reagent stream flows through a channel perpendicular to the droplet stream. An injection droplet is then merged with the plug as it passes the channel. Reagent volume is controlled by the flow rate of the perpendicular reagent channel. An early challenge for the T-Junction system is that reagent droplet merging was not reproducible for stable emulsions. By adapting the use of an actuated electric field into a T-junction setup, Abate et. al. achieved sub-picoliter control of reagent injection. This approach, termed picoinjection, controls injection volume through reagent stream pressure and droplet velocity. Further work on this method has aimed to reduce pressure fluctuations that impede reproducible injections. Droplet-to-droplet contamination is a challenge of many injection methods. To combat this, Doonan et. al. developed a multifunctional K-channel, which flows reagent streams opposite the path of the droplet stream. Utilizing an interface between the two channels, injection is achieved similarly to picoinjection, but any bilateral contamination washed away through continuous reagent flow. Contamination is avoided at the expense of potentially wasting precious reagent.

Reflective essay

1. I worked on the section titled "Droplet manipulation: reagent addition and droplet fusion". There were two paragraphs written on the droplet-based microfluidics page previously; however, these short paragraphs were disjointed and improperly cited. I wrote my section independently and since I am a consolidator, I will disperse the sentences worth keeping throughout my reagent addition section in an order that makes sense. 2. I added structure to the reagent addition methods section by grouping reagent addition methods. I provided a description of the function of different injection methods. I highlighted advantages and disadvantages of each method. I illustrated a simple chronology of injection technology development. 3. Peer reviewers helped better organize my thoughts. They highlighted redundant sections, which allowed me to cut down on space and to write in the information-dense style that works well on wikipedia. They also highlighted areas where I went into too much detail and became too technical for the wikipedia audience. Finally, they helped reword certain sentences for clarity and flow. 4. In regards to my own learning, this assignment was not valuable, as I found much of it to be redundant with the design project. While the design project demanded a technical understanding, much of that is not useful for a wikipedia article. While it is always a useful exercise to practice communicating technical subjects to a broader audience, this wikipedia assignment did not enhance my understanding of the topic of microfluidics.

I think my article is an improvement on the current section of reagent addition and droplet fusion. I think that my article and its cited sources provide a good jumping off point for someone beginning to study droplet-based microfluidic systems. In that sense, while I do not feel like my own knowledge of the subject matter was expanded, it is nice that the end goal of my assignment goes beyond just a grade and a document sitting on my computer never to be looked at again.

In the future, I think some more clarity of what our sandboxes/final products are supposed to look like will help. I found myself confused initially by what "article" menat - is this a standalone wikipedia page? Is it a section in a larger article? What does a good final article look like? I wasn't sure if I was on the right track for most of the time - and am still not entirely sure if the length/technicality of my article is adequate.