Quick measurement of electroosmotic flow velocity

Motohiko Nohmi and Juan Santiago present a simple way of estimating electroosmotic flow velocities in channel geometries with at least one intersection

Motohiko Nohmi, Fluid Machinery Research Center, EBARA Research Co., Ltd., Japan
Juan G. Santiago, Mechanical Engineering Department, Stanford University, CA, USA

Why is this useful?


We present a simple way of estimating electroosmotic flow velocities in channel geometries with at least one intersection.  The method is useful where a well-defined electrokinetic injection of a discrete plug of a neutral dye (the typical method, [1]) is not easily obtained given available equipment (e.g., when working with a primitive voltage sequencer or an insensitive CCD).

What do I need?


  • Microfluidic device with at least one intersection (Fig. 1)
  • CCD/CMOS camera
  • Epi-fluorescence microscope
  • Voltage control device that can switch potentials at two nodes
  • Neutral dye (e.g., 100 µM Rhodamine B)
  • Chemical buffers

Figure 1. Electrokinetic microchannel device with a simple Y-Channel topology. The end-channel potentials are V1, V2, and V3.

What do I do?


1. We assume here that the channel is expected to have a negative wall charge, but simple observations with a fluorescent solution can confirm this.  We add dyed solution to reservoir 1.  For a symmetric network (e.g., Fig. 1), keeping the sum V1+V2 constant will maintain a uniform electric field in the outlet Channel 3.

2. As a preliminary observation, vary V1 and V2 and test the limits which will initiate reverse flow in channels 1 or 2. Figure 2 shows example limits for a given maximum potential of (a) V1 = 1175 V, V2 = 925 V and (b) V1 = 925 V, V2 = 1175 V.  We’ll refer to these voltage limits as V1,high, V2,low, V1,low and V2,high.  (See [2] for predicting these voltages.)

Figure 2. Given a maximum (convenient) voltage limit V1,high = V2,high, voltages V1 and V2 can be adjusted to find suitable combinations of V1 and V2 which lead to zero back flow. (a) V1,high and V2,low (b) V1,low and V2,high.

3. The voltage controller should alternate V1 and V2 as shown in Fig. 3(a).  Experiment with t1 and t2 so that the flow has a noticeable disturbance propagating into channel 3 as shown in the movie of Fig. 3(b) (download below).  In Fig. 3(b), t1 and t2 are both 1 s, Vhigh = 1100 V, Vlow = 900 V and the image sequence was captured with 50 ms exposure time and 64.6 ms time-between-frames.

Figure 3. (a) One cycle of control voltages V1 and V2.  The duration of each of the two states is t1 and t2, respectively (typically t1 = t2).  Triangular or sinusoidal waves can be used, but require better equipment and a more complex setup.  (b) Visualization of flow showing propagation of disturbances flowing down channel 3 (see video below).

4. Capture an image sequence of modulated flow near the entrance of channel 3 (4-5 periods should be enough).  Extract the values of image intensity along the approximate centerline of the channel.  For better results, average a few pixel rows centered along the channel centerline.  Fig. 4 shows raw data for the dye intensity of the centerline of the 1st, 5th and 9th frame of an image sequence of the movie of Fig.3(b).  For a simple velocity estimate, analyze the second peak into the channel (where the velocity field is approximately parallel and fully developed).  From the two traces in Fig. 4, peak displacement over three frames is about Capital DeltaP1 = 20 pixels or u=k*Capital DeltaP1/Capital Deltatf= 131 µm/s (Eq. (1)).  Here k is the number of imaged microns per pixel, Capital DeltaP1 = 20 pixels , and Capital Deltatf is the time interval of the movie frame. You can also estimate velocity from the wavelength of the disturbance (and the known cycle time, 2 s):  u=k*Capital DeltaP2/(t1+t2)= 138 µm/s (Eq. (2)).  Here, Capital DeltaP2 (= 165 pixels) is the length between two dye peaks in a single image and t1+t2  is the cycle time of voltage modulation. These two approximate velocity measurements typically agree to within about 8%. The latter method is particularly useful when only a single image is available.

Equation (1).

Equation (2).

Figure 4. Dye intensity along the centerline of the 1st, 5th and 9th frames of of an image sequence of the propagating wave near the inlet of channel.

5. The methods described above are susceptible to noise in the image data, among other factors.  A more reliable technique uses multiple measurements and ensemble averages.  One way to accomplish this is using a fitting routine to analyze the waveform of Fig. 4.  We choose the following function:

Equation (3).

The coefficients of Eq. (3) can be estimated for each movie frame as shown in Fig. 5 (download below) by using the Gauss-Newton nonlinear least-squares data fitting routine “nlinfit” in MATLAB. The averaged wavelength Capital DeltaP2ave is calculated as 2Pi/C3ave  = 166.8 pixels and the averaged velocity is calculated as 140 µm/s using Eq. (2).  The velocity is also determined from the phase velocity C4 in Eq.(3) as follows.

Equation (4).

In Eq. (4), dC4/dt is calculated using a linear regression fit of the C4 data vs. time for 200 images. C4 changes linearly in time, and the phase velocity dC4/dt can be calculated by using a linear regression fit of the C4 data vs. time for 200 images. The wave travels one wavelength for the time of 2Pi/(dC4/dt), so the velocity of the fluid is determined as the averaged wavelength divided by 2Pi/(dC4/dt) as described in Eq. (4).

Figure 5. Spatial image intensity variation along channel centerline for a single image as a function of distance along the separation channel (in pixels). Shown with the data is a curve of the form of Eq. (3). (See .avi file below).

References


[1] S. Devasenathipathy and J. G. Santiago, “Electrokinetic Flow Diagnostics” in Micro- and Nano-Scale Diagnostic Techniques, ed. K. Breuer, New York, Springer Verlag, 2004.
[2] K. V. Sharp, R. J. Adrian, J. G. Santiago, and J. I. Molho, “Liquid Flows in Microchannels” in CRC Handbook of MEMS, ed. M Gad-el-Hak, CRC Press, New York, 2001, pp. 6-1 to 6-38.

Related links


Figure 3b .avi file
Visualization of flow showing propagation of disturbances flowing down channel 3.

Figure 5 .avi file
Spatial image intensity variation along channel centerline for a single image as a function of distance along the separation channel (in pixels).

Digg This
Reddit This
Stumble Now!
Share on Facebook
Bookmark this on Delicious
Share on LinkedIn
Bookmark this on Technorati
Post on Twitter
Google Buzz (aka. Google Reader)

27 Responses to “Quick measurement of electroosmotic flow velocity”

  1. Jess says:

    I’m just wondering what was the pH of the buffer that you were using?
    Thanks!

    (Report comment)

  2. Packers and movers assistance organization also take the finish assure of protection of family members item of client.

    Expert 5 Packers and Movers Delhi go to
    http://www.expert5th.in/packers-and-movers-delhi/

    Expert 5 Packers and Movers Gurgaon go to
    http://www.expert5th.in/packers-and-movers-gurgaon/

    Expert 5 Packers and Movers Chennai go to
    http://www.expert5th.in/packers-and-movers-chennai/

    Top 6 Packers and Movers Pune go to
    http://packersmoverspune.top3rd.in/

    Expert 5 Packers and Movers Hyderabad go to
    http://www.expert5th.in/packers-and-movers-hyderabad/

    Expert 5 Packers and Movers Bangalore go to
    http://www.expert5th.in/packers-and-movers-bangalore/

    Expert 5 Packers and Movers Mumbai go to
    http://www.expert5th.in/packers-and-movers-mumbai/

    (Report comment)

  3. Top packers says:

    useful links:-
    packers and movers in gurgaon @ http://top8th.in/packers-movers-gurgaon/
    packers and movers hyderabad @ http://top8th.in/packers-movers-hyderabad/
    packers and movers delhi @ http://top8th.in/packers-movers-delhi/
    packers and movers pune @ http://top8th.in/packers-movers-pune/
    packers and movers gurgaon @ http://www.list4pm.in/packers-movers-gurgaon/
    packers and movers bangalore @ http://www.list4pm.in/packers-movers-bangalore/

    (Report comment)

  4. They will specialize in generate move fast as well as even because of their top high quality
    Packers and Movers in Hyderabad @ http://www.expert5th.in/packers-and-movers-hyderabad/
    Packers and Movers in Mumbai @ http://www.expert5th.in/packers-and-movers-mumbai/
    Packers and Movers in Pune @ http://packersmoverspune.top3rd.in/

    (Report comment)

  5. You ought to discover assistance from your company that’s not merely very cost-effective but moreover efficient,
    Packers and Movers in Bangalore @ http://www.expert5th.in/packers-and-movers-bangalore/
    Packers and Movers in Delhi @ http://www.expert5th.in/packers-and-movers-delhi/
    Packers and Movers Gurgaon @ http://www.expert5th.in/packers-and-movers-gurgaon/

    (Report comment)

  6. It’s also sensible to talk to past clients regarding going companies to discover more on their particular consistency, abilities and also outstanding such as solutions and items.
    Packers and Movers Chennai @ http://www.expert5th.in/packers-and-movers-chennai/
    Packers and Movers Noida @ http://www.expert5th.in/packers-and-movers-noida/

    (Report comment)

  7. Usually because many going companies motivate not merely the system such as length and also judging by the amount items you should efficiently properly secured up as well as transport for your product new recognize.
    Movers and Packers in Mumbai
    Movers and Packers in Hyderabad

    (Report comment)

  8. Usually because nearly all movers motivate not just the system regarding comprehensive extensive comprehensive extensive variety
    Packers and Movers in Pune
    Packers and Movers in Bangalore

    (Report comment)

  9. Just About Establishing Residence Relocation Quick and Easy

    Ever move to a new location with all your residence belongings? Have you ever transferred from one town to another with your residential belongings? If yes then you might aware with problems, issues and demanding assignments related to the procedure of house relocation.

    About My Keywords:
    packers and movers pune
    packers and movers in pune
    movers and packers pune
    movers and packers in pune
    For More Information Please Visit Here
    http://www.top5quotes.in/packers-and-movers-in-pune.html

    (Report comment)

  10. There are specific issues and complications with relocating home to a new destination primarily packing, loading, moving, unloading, unpacking and rearranging of all your residential assets. But with suitable preparation and determining the best packers and movers services you can transform the process of residential shifting into lenient and easy project.

    About My Keywords:
    packers and movers Bangalore
    packers and movers in Bangalore
    movers and packers Bangalore
    movers and packers in Bangalore
    For More Information Please Visit Here
    http://www.top5quotes.in/packers-and-movers-in-bangalore.html

    (Report comment)

  11. Relevant planning is utmost required for a successful residential home relocation. Suitable planning of dwelling belongings with right packaging materials and sturdy packing containers is utmost mandatory whether you pack your possessions on your own or utilize trained packing solutions of shifting company. Proper packing ensures for safe and damage-free transportation of products from one area to another.

    About My Keywords:
    packers and movers Bangalore
    packers and movers in Bangalore
    movers and packers Bangalore
    movers and packers in Bangalore
    For More Information Please Visit Here
    http://www.top5quotes.in/packers-and-movers-in-bangalore.html

    (Report comment)

  12. If packing of items is carried out properly then there will be less chance of damages of them in transit. Be sure effective packing supplies and sturdy containers are used for packing of your residence possessions.

    About My Keywords:
    packers and movers gurgaon
    packers and movers in gurgaon
    movers and packers gurgaon
    movers and packers in gurgaon
    For More Information Please Visit Here
    http://www.top5quotes.in/packers-and-movers-in-gurgaon.html

    (Report comment)

  13. Thanks for sharing your info. I really appreciate your efforts and I will be waiting for your further write
    Packers and Movers in Hyderabad
    Packers and Movers in Bangalore
    Packers and Movers in Mumbai

    (Report comment)

  14. INSTAGRAM says:

    People discover <a href=" http://quickfansandlikes.comhow to get instagram followers without following anyone firmly obsessive as they quite simply like to expect photographs and see the numerous capabilities delivered by this social websites web site.

    (Report comment)

  15. SEO EXPERT says:

    There are dozens of online social media or social marketing and sharing portals out there, but one of the most important ones is how to get instagram followers 2015 . The portal is considered the best “visual marketing tool” of the moment, and if you upload a picture and you get enough likes you are already highly popular.

    (Report comment)

  16. visit page says:

    Great article Lot’s of information to Read…Great Man Keep Posting and update to People..Thanks

    (Report comment)

  17. This is such a great resource that you are providing and you give it away for free. keep up the good work.

    (Report comment)

  18. webpage says:

    great way of telling, and pleasant post to obtain facts on the topic of my presentation subject matter, which i am going to convey in institution of higher education.

    (Report comment)

  19. alan jack says:

    here
    [url=http://site.com/]anchor[/url]
    [url="http://site.com/"]anchor[/url]

    untuk Guest Book
    here

    ======

    http://www.produktabitaskincare.blogspot.com
    tabita skin care
    tabita skin care

    =============

    “Link to Wikipedia”:http://www.wikipedia.org

    ==============

    [WikiSyntax#Wiki-style_markup]

    And it will render as: WikiSyntax#Wiki-style_markup

    =============

    You can also provide some descriptive text. For example, the following
    link points to the

    [http://www.google.com Google home page].

    ========

    Markdown syntax
    [link title][http://foo.bar]

    (Report comment)

  20. anisa says:

    Catering Jakarta Konsultan Pajak Jasa Pemasaran Rental Mobil Video Editing Jasa Konsultan Pajak Sewa Mobil Jakarta http://birojasa.xyz Jasa Pemasaran Online Snack Box http://jasatraining.xyz Jasa Akuntansi Promosi Bisnis Online http://kursusonline.xyz Rental Mobil Jakarta Jasa Konsultasi Pemasaran Paket Pernikahan Jasa Video Shooting
    Catering Jakarta Konsultan Pajak Jasa Pemasaran Rental Mobil Video Editing Jasa Konsultan Pajak Sewa Mobil Jakarta http://birojasa.xyz Jasa Pemasaran Online Snack Box http://jasatraining.xyz Jasa Akuntansi Promosi Bisnis Online http://kursusonline.xyz Rental Mobil Jakarta Jasa Konsultasi Pemasaran Paket Pernikahan Jasa Video Shooting
    Rent Catering Info Konten Information Travel Marketing Jual Rumah Informasi Training Jasa Jual Beli Marketing Rumah Jasa Catering jasa training Jasa Akuntansi Little Forum Kursus Online Rental Mobil di Jakarta Lomba SEO Rumah Tangerang Jasa Company Profile
    canhr.info theregenerationroadmap.info youthalive.info
    produk kecantikan khasiat cream alami krim pemutih prdouk wajah unggulan krim pemutih ketiak produk kecantikan kosmetik wajah aman produk kecantikan wajah krim pemutih wajah herbal pemutih kulit badan krim pemutih jual baju wanita jual baju import grosir pakaian wanita grosi baju korea tas import branded butik tas online tas branded Jual Rumah Rumah Alam Sutera Rumah Dijual Alam Sutera Rumah Bintaro Rumah Dijual Bintaro Rumah BSD Rumah Dijual BSD Rumah Gading Serpong Rumah Dijual Gading Serpong Jual Apartemen jual apartemen aceh langsa jual apartemen bali badung jual apartemen bali denpasar jual apartemen kota cilegon jual apartemen banten serang jual apartemen tangerang jual apartemen alam sutera jual apartemen bsd tangerang jual rumah jual rumah banten jual rumah kota cilegon jual rumah serang jual rumah tangerang
    jual rumah tangerang alam sutera jual rumah tangerang bsd jual rumah tangerang gading serpong Jasa Bangun Rumah jasa bangun rumah jasa desain jasa desain arsitektur jasa desain furniture agen properti jual beli rumah jasa konsultasi properti jasa kontraktor jasa kontraktor contblock jasa kontraktor cor hotmix jasa kontraktor drainase jasa kontraktor instalasi listrik jual seragam kaos konveksi baju jual kostum bola sablon polyflex jual baju online
    Video Jasa Rumah Bangunan Jasa Arsitek Jasa Desain Interior Jual Paving Block Jual Pasir Jual Bata
    Biro Jasa Jasa Pemasaran pelatihan karyawan jasa akuntansi biro jasa perijinan Rental Mobil Jakarta Jasa Catering Jasa Video Shooting

    (Report comment)

  21. reda says:

    شركة تنظيف بالرياض
    شركة تنظيف فلل بالرياض
    شركة تنظيف بابها
    شركة تنظيف خزانات بالرياض
    شركة تنظيف منازل بالرياض
    شركة تنظيف مجالس بالرياض
    شركة تنظيف مسابح بالرياض
    شركة تنظيف قصور بالرياض
    شركة تنظيف واجهات بالرياض
    شركة تنظيف بالخرج
    شركة نقل اثاث بالرياض
    شركة نقل عفش بالرياض
    شركة تخزين عفش بالرياض
    شركة تخزين اثاث بالرياض
    شركة نقل اثاث بالدمام
    شركة نقل اثاث بجدة
    شركة نقل اثاث بمكة
    شركة نقل اثاث بالمدينة
    شركة مكافحة النمل الابيض بالرياض
    شركة مكافحة حشرات بالرياض

    شركة رش مبيدات بالرياض
    شركة مكافحة حشرات بجدة
    شركة رش مبيدات بجدة
    شركة مكافحة الحشرات بمكة
    شركة مكافحة حشرات بالدمام
    شركة رش مبيدات بالدمام
    شركة كشف تسربات بالرياض
    شركة كشف تسربات المياه بالرياض
    كشف تسربات
    شركة كشف تسربات المياه بجدة
    شركة تسربات المياه بالدمام
    شركة عزل خزانات بالرياض
    شركة عزل اسطح بالرياض
    شركة تسليك مجاري بالرياض
    شركة شفط بيارات بالرياض
    شركة تنظيف بجدة
    شركة تنظيف فلل بجدة
    شركة تنظيف شقق بجدة
    شركة تنظيف خزانات بجدة
    شركة تنظيف منازل بجدة

    شركة تنظيف بالدمام
    شركة تنظيف شقق بالدمام
    شركة تنظيف فلل بالدمام
    شركة تنظيف بالطائف
    شركة تنظيف بخميس مشيط
    شركة تنظيف مجالس بالبخار بجدة
    شركة تسليك مجاري بالدمام
    شركة تنظيف ببيشة
    شركة تنظيف بنجران
    شركة تنظيف بجازان
    شركة تنظيف وعزل خزانات بمكة
    شركة تنظيف بمكة
    شركة تنظيف وعزل خزانات بالمدينة المنورة
    شركة تنظيف فلل بمكة
    شركة تنظيف مجالس بالبخار بمكة
    شركة تنظيف بالمدينة المنورة
    شركة تنظيف بتبوك
    شركة رش مبيدات بتبوك
    شركة مكافحة حشرات بتبوك

    شركة تنظيف بالرياض
    شركة تنظيف خزانات بالرياض
    شركة تنظيف فلل بالرياض
    شركة تنظيف شقق بالرياض
    شركة نقل اثاث بالرياض
    شركة مكافحة حشرات بالرياض
    شركة رش مبيدات بالرياض

    (Report comment)

Leave a Reply