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Flashcards in QE11 Deck (11):

Name two chemicals used for anisotropic etching of silicon.



Stiction is a common problem encountered in releasing surface micromachined structures, name two methods to prevent stiction.

1. Coating of surface with hydrophobic self-assembled monolayer (SAM)
2. Supercritical fluid drying method


What is SU8 and where is used the most?

SU8 is a negative photoresist mask and it is used for high-aspect ratio etching in thick photosensitive polymers.


Name two reasons why PDMS is a good substrate for microfluidics.

1. Porous
2. Simple processing


Name two advantages of capacitive sensing over piezoresistive sensing.

1. No doping requirements
2. Low noise


What is Reynold # and why is it important in microfluidics? What is the equation?

The Reynold's number quantifies flow and thermal transfer characteristics. Re=V*L/v where V is the velocity, L is the length scale and v is the kinematic viscosity.


What is electric double layer capacitance?

Electric double layer capacitance is when an ionic solution is placed over a substrate and positive ions flow over negative ions that are attracted to the substrate


Why do you need to remove silicon from underneath thermal sensors?

Having silicon underneath thermal sensors increases the effective resistance (silicon acts as a heat sink) and reduces the sensitivity


Can you measure a physiological signal having a close to DC frequency response with a piezoelectric sensor?

It is difficult because there is a degraded response at low frequencies.


Commercial glucose sensors are electrochemical ampiometric sensors. What is meant by electrochemical ampiometric?

A change in the chemical concentration of glucose changes the amount of current flowing in the device. This is detected electrically.


How is the kinematic viscosity related to the dynamic viscosity?

kinematic = v = mu / rho (mu is the dynamic)