Client Contact
Dr. Devendra S. Kalonia, Ph.D.
Associate Professor of Pharmaceutics
Department of Pharmaceutical Sciences
University of Connecticut, U-2092
Storrs, CT 06269
(860)-486-3655 (phone)
(860)-486-4998 (fax)
In the pharmaceutical industry a wide range of new technologies are emerging to keep pace with drug development and manufacturing. In order to facilitate this new wave of technology we have sought out improving a piezoelectric device that will determine the rheological properties of liquids/semi-solid mixtures, at low volumes and with a broad frequency range which will help formulate stable protein drugs. This piezoelectric device will measure the impedance frequency formulated by the viscosity of a liquid due to shear stress of the fluid over a crystal plate. This type of acquired information will be significant to drug scientists who anticipate understanding the physical properties of the product. This technology will not only aid in drug research but will also save money due to its ability to measure minute quantities, less than 20 micro liters. Since financial stability is necessary for any research, improvement of the piezoelectric device will follow on this matter.
Currently there are many products on the market that are able to measure fluid viscosity. However, most require samples in the milliliters (Table 1). In the pharmaceutical industry the developing product can be extremely expensive or limited in quantity. Sacrificing milliliters of the product could be costly. Recent research (Saluja and Kalonia, 2004) has taken steps in addressing this problem. With the use of piezoelectric crystals Saluja and Kalonia were able to determine rheological characteristics of various fluids in volumes as small as 8-10 micro liters.
|
Product Type* |
Company* |
Product Name* |
Sample Size* |
Price** |
|
Capillary flow viscometer |
Cannon Instrument (State College, PA) |
Cannon Manning Semi-Micro Viscometer |
0.5 mL |
$105 |
|
Cone and Plate viscometer |
Brookfield Engineering Laboratories (Middleboro, MA) |
Wells-Brookfield Cone/Plate |
0.5 mL |
$1645-2895 |
|
Rotating Cup and Bob |
Brookfield Engineering Laboratories (Middleboro, MA) |
Brookfield Viscometer |
2mL |
$3295-3895 |
|
Rotating Cup and Bob |
Anton Paar (Ashland, VA) |
Automated Falling Sphere Microviscometer |
150uL |
? |
Table 1: Current Rheometric devices on the market (* taken from Saluja and Kalonia, 2004; ** taken from distributors’ websites and catalogs)
However, each piezoelectric crystal can only vibrate at one frequency. In order to accurately determine the fluid’s properties it is necessary to make measurements at varying frequencies.
Basic Limitations
Though this project is seemingly straightforward, there exist a number of problems and limitations that may be encountered throughout the design and construction of the device. The mission statement requests a piezoelectric device which produces shear waves at a variety of frequencies with capabilities of measuring the impedance of liquids/semisolids on a micro liter scale. These specifications lend to an array of limitations. The purpose of a machine which can utilize such small measures of liquid is to not only reduce waste of material, but also to cut costs, as these liquids are very expensive. As such, to produce a piezoelectric device; which relies on a crystal that produces waves at one given frequency, that can function on a plethora of frequencies, this project is limited by the number of crystals that can be used. If, in order to create a range of frequencies, several crystals are used, more liquid would be required for each crystal, thus increasing the costs and defeating the purpose of a low budget device.
This device in question is to be used specifically for very small amounts of a product. Due to this size constraint, evaporation of the liquid will also pose a possible problem for design. Any changes due to evaporation, or contamination, of the liquid on a micro liter scale could result in skewed data, and tainted findings. Thus, the device must either record data fast enough to offset the possible threat of evaporation, or some sort of containment must be assembled so as to prevent any liquid from vaporizing.
Not only will cost and outside elements create limitations on the design, but the actual movement of the fluid as a load on a crystal could also affect the outcome. The crystal is to produce shear waves, as a sort of horizontal movement back and forth. The fluid in question will likely be placed directly on a gold disc, which coats the crystal. The movement of the crystal may shift the fluid on top, spreading the liquid around the gold disk. In theory this would not cause a dilemma, unless the fluid spread onto the actual crystal, possibly damaging it. Thus, the design should limit the movement of the fluid on the coating of the crystal, so as not to damage the device and alter results.
Questions
1. In relation to our design, how do similar products function, and how were they constructed?
2. Is it possible to manipulate a crystal so as to create a wide range of frequencies?
3. What program should be utilized for our data output. How should the data be configured?
4. Are there other devices that create shear waves similar to the ones we will be working with?
5. Are there alternatives to piezoelectric device setups, namely devices that do not produce shear waves/stress?
6. How sensitive to volume can we design the device?
Other Data
This design is being pursued by the request of:
Dr. Devendra S. Kalonia, Ph.D.
Associate Professor of Pharmaceutics
Department of Pharmaceutical Sciences
University of Connecticut, U-2092
Storrs, CT 06269
(860)-486-3655 (phone) (860)-486-4998 (fax)