T-sensors

A.E. Kamholz, B.H. Weigl, B.A. Finlayson, and P. Yager, Quantitative analysis of molecular interaction in a micro fluidic channel the T-sensor. Anal. Chem. 71, 5340—5347 (1999). 

Munson MS, Hasenbank MS, Fu E, Yager P (2004) Suppression of non-specific adsorption using sheath flow. Lab Chip 4 438 145 Munson MS, Hawkins KR, Hasenbank MS, Yager P (2005) Diffusion-based analysis in a sheath flow microchannel the sheath flow T-sensor. Lab Chip 5 856-862... 

Aiba, H. Nagaya, M. Mizuno, T Sensor and regulator proteins from the cyanobacterium Synechococcus species PCC7942 that belong to the bacterial signal-transduction protein families implication in the adaptive response to phosphate hmitation. Mol. Microbiol., 8, 81-91 (1993)... 

Mobius, H., Ehrfeld, W., Hessel, V., Richter, T., Sensor controlled processes in chemical microreactors, in Proceedings of the 8th Int. Conf on Solid- State Sensors and Actuators, Transducers 95 -Eurosensors IX (25-29 June 1995), Stockholm, 1995, 775-778. 

FIGURE 10.6 Schematic diagram of flow and diffusion within the T-sensor at a 1 1 1 flow ratio. A reference solution enters the device from the left, a detection solution from the middle, and a particle-laden sample stream enters from the right. The inset shows (1) original flow boundaries, (2) reference stream, (3) particle-laden sample stream, (4) diffusion of detector substance into reference stream, (5) diffusion of reference substance into detector stream, (6) detection stream, (7) diffusion of sample analyte into detection stream, (8) diffusion of detector substance into sample stream, and (9) detector window [443]. Reprinted with permission from the American Association for the Advancement of Science. 

FIGURE 10.7 Competitive diffusion immunoassay analysis for phenytoin using a T-sensor as shown in Figure 10.6. Plots of fluorescence intensity versus channel width dimension, as the concentration of unlabeled phenytoin increased from Oto 573 nM [1015]. Reprinted with permission from Nature Publishing Group. 

FIGURE 10.17 Schematic of microfluidic device consisting of an H-filter for cell lysis/fractionation coupled to a T-sensor for detection of an intracellular enzyme (( -galactosidase). Pump rates are controlled at all inlets and one outlet. In the H-filter (left), lytic agent diffuses into the cell suspension, and lyses the cells. Intracellular components (enzyme) then diffuse away from the cell stream and some are brought around the corner into the detection channel. In the T-sensor (right), the presence of (1-Gal is detected fluorescently [1051]. Reprinted with permission from the American Chemical Society. 

Describe what are employed in the three streams in a T-sensor for immunoassay. (3 marks)... 

Weigl, B.H., Kriebel, J., Mayes, K., Yager, P., Wu, C.C., Holl, M., Kenny, M., Zebert, D., Simultaneous self-referencing analyte determination in complex sample solutions using microfabricated flow structure (T-sensors). Micro Total Analysis Systems 98, Proceedings pTAS 98 Workshop, Banff, Canada, 13-16 Oct. 1998, 81-84. 

Figure 3 Functional scheme of recording block (microcontroller) 1- GPU, 2-ROM, 3-RAM, 4- timer, 5 - power supply, C - bus, 7-11 - PIA, 12 - serial interface, 13- key-board/display, 14-17 - voltmeter, 18 - P-sensor, 19- T-sensor, 20- V-sensor, 21- sample, 22 - port RS-232S (communication with computer).

Hatch A, Kamholz AE, Hawkins KR, Munson MS, Schilling EA, Weigl BH, et al. A rapid diffusion immunoassay in a T-sensor. Nat Biotechnol 2001 19 461-465. 

Hauptman, P. Pownall, T. Sensors principles and applications Prentice-Hall New York, NY, 1993... 

This chapter focuses on fluid flow, leaving the combination of fluid flow, heat transfer, and diffusion to Chapter 11. Examples of fluid flow include entry flow into a pipe, flow in a microfluidic T-sensor, turbulent flow in a pipe, time-dependent start-up of pipe flow, flow in an orifice, and flow in a serpentine mixer. The examples demonstrate many of the techniques that are useful in the program FEMLAB. 

Next consider flow in what is called a T-sensor. Two flows come together, join, and traverse down one channel, as illustrated in Figure 10,9, This device is used in microfluidic medical devices, which are discussed further in Chapter 11, Here you will consider only the flow (which has no special utility until the convective diffusion equation is added in Chapter 11),... 

Figure 10.12. Streamlines in a T-sensor when the inlet velocity is paiaholic.

Solve the example of a microfluidic T-sensor, except have the average velocity coming in the bottom twice as high as in the example. Compare the flow rates in both streams and out to ensure that the total flow in equals the total flow out. 

The T-sensor was described in Chapter 10, but its key use is to transfer a chemical from one flowing stream to the other. Thus, the convective diffusion equation must be solved, too. A fluid (such as water) comes in the top and bottom, but the top stream contains a dissolved chemical that needs to be transferred. The bottom stream may contain a different chemical that will react and fluoresce, thus permitting a visual detection. Your goal is to predict how fast the transfer will take place. See Hatch et al. (2001) and Wiegl et al. (1999). 

Step 1 It is easy to add the convective diffusion equation by starting with the fluid flow model of the T-sensor. Choose Multiphysics/Model Navigator. A window appears with a hst of possible equations. Scroll down and select Chemical Engineering Module/Mass Balance/Convection and Diffusion/Steady-state Analysis. Click Add. Now FEMLAB will solve both equations. 

Figure 11.4. Solution to T-sensor diffusion/convection problem with D = 1-...

Then the viscosity of the material coming into the top of the T-sensor is 2 whereas the viscosity coming into the bottom is 1. This model was solved by Marlina Lukman when she was a senior chemical engineering student at the University of Washington. To modify the model, perform the following steps. 

This chapter illustrated the use of FEMLAB for problems of heat conduction, heat conduction and convection, and mass diffusion and convection. Problems included heat conduction in a 2D plane, several microfluidic devices (T-sensor and serpentine mixer), and heat effects in orifice flow. Specific methods demonstrated in FEMLAB include ... 

Solve the flow and diffusion problem for the T-sensor, as illustrated in the example. Then consider a similar flow problem with water coming in both inlets. However, one inlet contains one chemical, identified as A, and the other inlet contains another chemical, identified as B. The two react with the reaction rate... 

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