Design, development, and applications of quartz crystal microbalance are discussed. Two types of crystals are used. One serves as reference and other senses changes in mass. Specific application to study of bacterial spores is described

Godfrey, J. F.

Green, R. H.

Laue, E. G.

Laue, T. M.

Paik, W. W.

Wardle, M. D.

English

NASA Technical Reports Server

August 1972
	 B72-10243 
NASA TECH BRIEF 
NASA Pasadena Office 	 4r 
NASA Tech Briefs announce now technology derived from the U.S. space program. They are issued to encourage 
commercial application. Tech Briefs are available on a subscription basis from the National Technical Information 
Service, Springfield, Virginia 22151. Requests for individual copies or questions relating to the Tech Brief program may 
be directed to the Technology Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
Quartz Crystal Microbalance Used in Biological Studies 
Quartz crystals have been used as sensitive micro-
balances to detect changes in mass of the order of 
10 11 g. For this purpose, the crystals are used as 
oscillators; the fundamental frequency of a crystal 
is changed when a mass of material is deposited on 
its surfaces. The change in frequency that is observed 
with similar crystals (same cut, etc.) for equal mass 
increments is nearly the same, but since the sensi-
tivity to mass changes as a function of temperature 
and is somewhat variable from crystal to crystal, a 
calibration factor must be established under con-
trolled environmental conditions for each crystal. 
Two-crystal microbalances have been used in stu-
dies of the relationship between spore survival and 
mass change when spores are exposed to various 
conditions of temperature, humidity, and vacuum. 
Four two-crystal systems are used in conjunction 
with identical monitoring systems and a vacuum 
chamber which includes nine resistance-heaters and 
four temperature sensors. The chamber can be 
brought to a temperature of 125°C in about two 
minutes, and it has been designed to minimize the 
mass and volume to be heated. Its size is such that 
it can be inserted into an available constant-humidity 
cabinet. 
The crystals may be used individually, in a variety 
of combinations, or in pairs with one crystal as a 
reference and the other as a sensor for changes of 
mass. Two types of crystals have been used, one 
being stable at 25°C and the other at 125°C. Each 
crystal is connected by a triaxial cable to its asso-
ciated oscillator circuitry; the inner shield is fed with 
voltage in phase with the "hot" lead from a low-
impedance source in the oscillating circuit and the 
outer shield is the crystal voltage return. This ar-
rangement minimizes capacitance effects between the 
crystal and the oscillator input; more importantly, 
however, it is possible to separate the crystal from 
the oscillator circuit by distances up to twelve feet 
at a frequency of five megahertz. 
Studies of the effect of vacuum on a mass of bac-
terial spores were performed with the quartz crystal 
microbalance. A quartz crystal was seeded with 10 
microliters of an aqueous suspension of B. svbtili8 
var. niger (109 viable spores per ml); the other was 
operated as the control. The inoculated crystal was 
allowed to dry at 24°C and a relative humidity of 
46 percent. Application of a vacuum produced a 
mass loss of 6.8 micrograms; upon release of the 
vacuum, the regained mass over a period of 8 min-
utes corresponded to 0.5 microgram, but the total 
mass gain rapidly became 6 micrograms after an 
additional equilibration period of 4 minutes. 
In another series of tests, 5.3 X 101 bacterial spores 
were brought to a temperature of 125°C. Typically, 
30-minute heating periods caused losses of 1.2 to 
3.6 micrograms; from 11 to 14 percent of the spores 
survived. On the other hand, for 60-minute periods 
of exposure at 125°C, only 1.4 to 1.5 percent of the 
spores survived; weight losses ranged from 4.2 to 
8.1 micrograms. 
(continued overleaf) 
This document was prepared under the sponsorship of the National	 Government assumes any liability resulting from the use of the 
Aeronautics and Space Administration. Neither the United States	 information contained in this document, or warrants that such use 
Government nor any person acting on behalf of the United States	 will be free from privately owned rights.
S
https://ntrs.nasa.gov/search.jsp?R=19720000243 2020-03-17T03:28:07+00:00Z
Note: 
Requests for further information may be di-
rected to: 
Technology Utilization Officer 
NASA Pasadena Office 
4800 Oak Grove Drive 
Pasadena, California 91103 
Reference: TSP 72-10243
Patent status: 
No patent action is contemplated by NASA. 
Source: Richard H. Green, James F. Godfrey, 
Eric C. Laue, Thomas M. Laue, William W. Paik, 
and Michael D. Wardle of 
Caltech/JPL
under contract to
NASA Pasadena Office 
(NPO-11346) 
B72-10243	 Category 05


Quartz crystal microbalance use in biological studies

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server