Assignment #3

Total : 50 (the individual marks are enumerated in parentheses at the end of every question)

Answer in 1-2 lines

(1)Draw the schematic and explain the functionality of an Ammonia sensor. [3]

(2)Explain how you will sense the following metabolites. Penicilllin, Glucose, Urea,

Creatinine, L-Phenylalanine and Adenosine. Give a few lines indicating the reason why

we should sense these metabolites. [6]

(3)Explain the interfacial double layer phenomena with a schematic.[2]

(4)Derive a mathematical expression for the zeta potential in terms of the electrostatic

double layer, surface charge density and dielectric constant. [3]

(5)Derive a mathematical expression for the electro-osmotic mobility for a charges

surface. [3]

(6)An infinite plate is moved over a second plate on a layer of fluid as shown in figure 1.

For the small gap width, d, we assume a linear velocity profile in the fluid. The fluid

viscosity is 0.65X10-3 kg/ m.s and its specific gravity is 0.88. Calculate:

The Kinematic viscosity of the liquid, in m2/s.

The shear stress on the lower plate in Pa.

Indicate the direction of each shear stress indicated in part(b).

Figure 1 [5]

(7)The velocity distribution for a laminar flow between fixed parallel plates is given by

the following expression.

u/umax = 1- (2y/h)2

Where h is the distance between the plates and the origin is placed half way between

the plates. Consider the flow of water at 15deg. C with a maximum speed of 0.05 m/s

and h=5mm. Calculate the force on a 0.3mm2 section of the lower plate and give its

direction. [6]

(8) Derive a mathematical expression for the streaming potential due to a pressure

head P in terms of the flow rate and streaming current. [3]

(9) Find two sensory applications of streaming potentials online. A brief description with

a schematic should be provided where streaming potential is used as a sensing

mechanism. [3]

U=0.3 m/s

x

y

d= 0.3m

(10) Derive a mathematical expression for electrophoresis. [3]

(11) The electrokinetic pumping network shown below [see fig.2 ] is used for capillary

electrophoresis. Ports 1 and 2 are the inlet and outlet for a sample, respectively. Port 3

is the inlet of the carrier buffer. The longest channel is the separation line. Port 4 is the

waste port. All microchannels are etched in glass and have a diameter of 100 microns.

The channel lengths are depicted in figure 2. Measuring electrical impedance across

ports 1 and 2 results in 400Mohms. The potential at ports 1,2,3 and 4 are 1000V, 1000V,

1500V, and 0V respectively. Do the fluids from 1 &2,contaminate the separation

process? Assume the sample solution and buffer have identical electrokinetic

properties.

Figure 2 [5]

(12) Draw and explain the basic DNA structure. Mention about the difference in

hydrogen bonding between the 4 bases and why this is so important? [2]

(13) What is stringent and reduced stringency hybridization? [1]

(14) Describe with a schematic the polymerase chain reaction process. [1]

(15) What is Real Time PCR? Explain about the various phases of a full PCR cycle with

respect to one cycle and a no. of cycles. [1]