ECE5320 Mechatronics Assignment#01: Literature Survey on Sensore and Actuators Topic: Quartz Crystal Microbalances Prepared by: Jack J Stepan Dept. of Electrical and Computer Engineering Utah State University E: T: (435) F: (435) (ECE Dept.) W: 3/11/2005

Outline Reference list To probe further Major applications Basic working principle illustrated A typical sample configuration in application (application notes) Major specifications Limitations And many more relevant issues in application (such as, how to choose, cost information, where to buy etc.)

Reference List oup/contents/instrumentation/QCM/QCM.htmhttp:// oup/contents/instrumentation/QCM/QCM.htm QCM-Z500_Article.pdfhttp:// QCM-Z500_Article.pdf

To Explore Further (survival pointers of web references etc) This is a specific sensor, so websites are fairly straightforward. Some websites have glossaries that are informative Also try searches for nanotechnology and quartz crystals Some of the reference list websites contain references for further reading

Major Applications Thin film thickness monitoring Biotechnology Functionalized surfaces Thin film formation Surfactant research Drug research Liquid plating and etching Particle detection

What is a QCM ? (quartz crystal microbalance ) The QCM is a piezoelectric device capable of extremely sensitive mass measurement with nanogram sensitivity.

How does it work? 3 easy steps 1.The quartz crystal is oscillated by an alternating, high frequency electric field applied by the electrodes 2.If any mass sticks to the surface, the resonant frequency of the crystal changes 3.The change in frequency is measured and the change in mass can be calculated by the Sauerbrey equation

Sauerbrey Equation:

You will also need… An oscillator –A circuit that produces the signal to oscillate the crystal A holder –To aid in handling the crystal which you can’t touch Frequency counter –To measure the change in frequency Temperature monitor –Keeps the temperature in the operating range

Accessories Most manufacturers provide all the necessary electronics and equipment here are a few things that come in handy: PC –Often a data interface is available Flow chamber –So only the desired fluids are in contact Cleaning supplies –Deionized water, cleaning basket, and other chemicals as necessary

Typical setup This is an electrochemical setup from scratch; most suppliers have the entire setup already available

Major Specifications Frequency Range –The frequencies at which the QCM is operable Frequency Tolerance –The amount of frequency deviation from a specified center frequency at ambient temperature Frequency Stability –The amount of frequency deviation from the ambient temperature frequency over the operating temperature range

Major specs. cont’d Temperature Range (operating and storage) –The minimum and maximum temperature for which the deviation from the nominal frequency will not vary by a given amount Shunt Capacitance –The capacitance derived from the dielectric of the quartz, the area of the electrodes and the holder Load Capacitance –The value of capacitance used in conjunction with the crystal unit (user specified)

Major specs cont’d Drive Level –The amount of power dissipation in the crystal. Maximum power is the most power the device can dissipate while still maintaining operation with all electrical parameters guaranteed Aging –A systematic change in frequency and or resistance with the passage of time due to internal changes in the crystal

Sample specs

Features Nanogram resolution! Real time capability- frequency and therefore mass, can be monitored as a function of time Non-corrosive, it can handle wide range of chemicals High signal to noise ratio Now has measurement ability in liquids

Limitations Nanogram resolution, but can’t measure larger masses Molecules or particulates must stick to the surface. Extensive preparation is usually required to accomplish this Aging -it just wears out Temperature sensitivity -measurements limited to relatively small temperature range

What is available? Gold, silver, platinum and other metal electrodes Varying temperature ranges and range sizes Varying frequency ranges and range sizes Specialized for gas or liquid measurement

Where to buy This is an expensive sensor, a total unit package from SRS costs $1000 Ten crystals are about $300 BIE department setup worth over $3000

Closed Loop Control With a QCM This sensor is usually not used in control systems, but… Bio-engineers are working on coatings that could allow QCM’s to repeatedly sense viruses or other pathogens in the air. This could be useful in an automated system that filters disease from the air in buildings. Or as an automatic warning for biological weapons QCM’s could also be part of automatic manufacturing of membranes or monolayers in nanotechnology There are many possibilities….