Charles E. Bouldin
DMR Division of Materials Research
MPS Directorate for Mathematical & Physical Sciences
Start Date:
September 1, 2006
Expires:
August 31, 2009 (Estimated)
Awarded Amount to Date:
$94502
Investigator(s):
Rafael Tadmor rafael.tadmor@lamar.edu (Principal Investigator)
Sponsor:
Lamar University Beaumont
4400 Port Arthur Road
Beaumont, TX 77705 713/838-7011
NSF Program(s):
MAJOR RESEARCH INSTRUMENTATION
Field Application(s):
0106000 Materials Research
Program Reference Code(s):
AMPP, 9161
Program Element Code(s):
1189
ABSTRACT
Technical Abstract
A first instrument of its kind to measure lateral adhesion forces between drops and surfaces will be build in Lamar University. The instrument will use centrifugal forces to drive drops past contacting surfaces. The centrifugal arm could tilt so that it would be either horizontal or perpendicular with respect to gravity. The horizontal alignment will allow measurements of drop-surface lateral adhesions of any practical force as opposed to the very weak adhesive force limitation of the current tilt stage method. In the vertical alignment, however, the centrifuge will modify the normal force until the drop will slide down due to gravity. With this, a complete decoupling of the normal and lateral components will be possible. Such decoupling will open a way for measurements that are otherwise impossible, leading to breaking ground research that is currently inaccessible. For example, the modified Young equation shows linear proportionality between the line energy per unit length, k, and the radius of the drop. Therefore to keep k independent of line length, the contact angle should change considerably with drop size. As shown by many investigators, experimentally this does not happen, the contact angle changes negligibly, if at all, with drop size. The proposed instrument will address this long standing discrepancy between theory and experiment (just to name one example).
Lay Abstract
Drops contact angle on surfaces serve as one of the most common ways for surface characterization in a wide variety of fields. The vast use of drops as characterization tools is in part due to its relative simplicity, yet, there are many puzzles associated with the physical understanding of this phenomenon, as well as limitations on the systems with which drop can be used as a characterization tool. The instrument that we will build at Lamar University will address these issues. It will address the current limitations by allowing any drop to reach its maximal and minimal contact angles, which correspond to the force required to slide the drop past the surface. Thus it will allow proper drop characterization for systems that could not have been characterized with older techniques. It will also address the physical understanding (in addition to what will emanate from the increase in available systems) by allowing to vary the force required to slide the drop without varying at the same time the force by which the drop presses on the surface (this is the only way currently to vary the sliding force without varying the normal pressing force). This feature of independent manipulation of the force parallel to the surface will revolutionize surface science as it allows addressing long standing puzzles in the field. For example the long standing question: why the contact angle does not change with drop size as expected theoretically.
PUBLICATIONS PRODUCED AS A RESULT OF THIS RESEARCH
(Showing: 1 - 5 of 5).
Tadmor R.
"Line energy, line tension and drop size,"
Surface Science,
2008,
Tadmor, R; Peppert, KG.
"Interfacial tension and spreading coefficient for thin films,"
LANGMUIR,
v.24,
2008,
p. 3185
- 3190.
Tadmor, R; Yadav, PS.
"As-placed contact angles for sessile drops,"
JOURNAL OF COLLOID AND INTERFACE SCIENCE,
v.317,
2008,
p. 241
- 246.
Yadav, PS; Bahadur, P; Tadmor, R; Chaurasia, K; Leh, A.
"Drop retention force as a function of drop size,"
LANGMUIR,
v.24,
2008,
p. 3181
- 3184.
Yadav, PS; Dupre, D; Tadmor, R; Park, JS; Katoshevski, D.
"Effective refractive index and intermolecular forces associated with a phase of functional groups,"
SURFACE SCIENCE,
v.601,
2007,
p. 4582
- 4585.
(Showing: 1 - 5 of 5).
Please report errors in award information by writing to: awardsearch@nsf.gov.
