The Interfacial Physics Group

Carnegie Mellon University, Department of Physics



Marangoni Driven Spreading on Entangled Polymer Solutions WithApplications to Pulmonary Drug Delivery

Inhaled aerosol drugs can deliver substantial doses of medication directly to the lungs while minimizing the exposure of the rest of the body to the medication, greatly reducing the possibility ofside effects.Antibiotics are often administered this way for treatment of the pulmonary infections associated with cystic fibrosis. Aerosols (fine droplets of liquid suspended in air) are mainly transported through the lung in the air stream duringinhalation. However, obstructions in the airways and otherconsequences of cystic fibrosis lung disease may cause inhaled droplets containing drugs to be deposited non-uniformly so that some lung regions receive very high local doses of medication, while other regions go untreated. We are exploring how to incorporate surfactants into the aerosol formulations so when the aerosol drops land, surface tension gradients are created and drug in driven along the surface of the airways. To investigate this and other potential lung therapies using surfactants, we have assembled a multidisciplinary team of scientists, engineers and clinicians from various departments at Carnegie Mellon and the University of Pittsburgh.


wetting imageWetting and spreading are ubiquitous in nature and technology. Static wetting, often characterized by the contact angle, is controlled by the balance of at the contact line. Dynamic wetting is more complex since the fluid flow near the contact line causes viscous forces on the interfaces in addition to the capillary forces. These viscous forces become dominant as the contact line is approached. Thus, wetting phenomena we observe and attempt to control on the macroscopic scale are controlled by the physics and chemistry in the microscopic region near the contact line, a region where the static and dynamic behavior of the fluid may be different than in the bulk phase. We study a number of aspects of static and dynamic wetting.

Colloidal Forces and Movement in Electric Fields

colloid imageColloidal dispersions contain small, typically micron scale, solid particles suspended in a fluid. The stability and rheology of these dispersions depend on the forces between the colloidal particles. The particles can often be moved by fields applied to the suspension. In recent years we have investigated two aspects of colloidal forces and the manipulation of particles in electric fields.

Origins of Friction-Driven Vibrations

friction imageCurrent knowledge is insufficient to reliably predict when a vehicle braking system will squeal. This problem, in common with many others involving friction-induced vibration, remains intractable because of significant shortcomings in the modeling of friction at interfaces. Our ultimate goal is to produce an experimentally verified model that identifies the key variables relevant to producing friction induced vibrations and to determine the sensitivity of the threshold for this vibration to those variables. We ask why in some systems, the friction induced vibration produces the harsh squeal of a brake while on a violin (in the hands of a skilled player) it produces a rich tone.

Applied Projects

applied imageOur groups seeks projects where we can apply the fundamental knowledge about interfacial physics and chemistry to technological problems. We have undertaken a number of such projects in the past and welcome opportunities to participate in more such projects in the future. Recent projects include:


  • Development of Instrumentation for In-situ Quality Control Measurements of Wettability
  • Coatings on Windshields
  • Mechanics of Fiber Glass Chopping
  • Role of Wetting in Processing of High Volume Fraction Polymer/Particle Composites
  • Role of RF Fields In Wettting
  • Polymer Coating During Fiber Glass Forming Processes
  • Complex Fluid Engineering for Pharmaceutical Unit Operations
  • Origins in Wetting Enhancement and Colloidal Stability by Surfynol Surfactants for Semiconductor Processing
  • Wetting Issues in Liquid Immersion Lithography