Jeffrey M. Davis

Associate Professor

259B Goessmann Lab
413-545-2916 (Office)
413-545-1647 (FAX)
jmdavis@ecs.umass.edu

Education

S.B., Massachusetts Institute of Technology, 1999
M.A., Princeton University, 2001
Ph.D., Princeton University, 2003

Recognitions

3M Nontenured Faculty Award, 2006
Honorary Teaching Award, UMass Chemical Engineering, 2006
NSF CAREER Award, 2007
Outstanding Teacher Award, University of Massachusetts, College of Engineering, 2007
Lilly Teaching Fellowship, 2007
Camille Dreyfus Teacher-Scholar Award, 2007

Current Focus of Research

*  Microscale Fluid Dynamics
*  Interfacial Flows
*  Hydrodynamic Stability and Pattern Formation

The focus of Professor Davis’ research is the development of mathematical models to provide a fundamental understanding of microscale fluid dynamics on heterogeneous surfaces.This heterogeneity results from chemical patterning, topographical variations, and differential heating of the substrate, all of which lead to significant deviations from fluidic behavior on uniform surfaces. Flows over these non-uniform surfaces are crucial to applications that include microfluidic analytical devices and sensors, micro-electro-mechanical systems, and micro-fabrication processes.  This research has two major thrusts: (1) free-surface flows on heterogeneous surfaces that enable improved performance and fabrication of micro-devices and (2) particle dynamics in flow over nanotextured surfaces that form the basis for biomimetic sensors.

1.  Micro-scale free-surface flows over heterogeneous surfaces
Microfluidic devices, selective deposition processes, and micro-fabrication techniques require a detailed understanding of liquid film dynamics on heterogeneous surfaces.  For example, centrifugal spreading over surfaces with topographical features is crucial to the manufacture of microelectronic products.  The topographical features may be either unwanted (dust, scratch, or defect) or regular features (patterning; previously deposited layer) essential to the coating process.  Similarly, non-uniform heating leads to gradients in surface tension (Marangoni stresses).  These gradients can induce flows that adversely affect the shape of a deposited liquid film or lead to hydrodynamic instabilities that produce regular patterns with nontrivial macroscopic order and break the uniformity of the coating.  Examples of such instabilities are shown in Fig. 1.
In these free-surface lubrication flows (i.e., creeping flows with small height to length ratio), capillary, thermocapillary, Marangoni, and van der Waals interactions can dominate the fluid dynamics and lead to qualitative differences from bulk flows. The combined effects lead to fascinating dynamical behavior because the shape of the liquid-gas interface changes spatially and temporally, and the velocity field is coupled to the shape of the free-surface.  A fundamental understanding of these flows and their stability is required to design more effective transport and containment processes.

2.  Confined microfluidic flow over nano-textured surfaces
The Davis group has developed computational models and is collaborating with the experimental groups of Professors M. Santore and E. Coughlin in Polymer Science and Engineering at UMass to design nanopatterned surfaces that manipulate the adhesion (capture from free solution) and interfacial motion signatures (rolling, sliding, skipping, stick-slipping) of micron- and submicron- scale objects in shear flow.  These systems form the basis for biomimetic sensors that can, for example, mimic the rolling and capture of white blood cells near the site of an injury based on the force-sensitive interactions between cellular receptors and ligands near the injured tissue.  Artificial molecules are used to create chemical heterogeneity on the surfaces at nanometer lengthscales. Flat 5-20 nm patches of controlled chemistry are attached with an average spacing of 1-100 nm to sensor surfaces, creating spatially varying colloidal forces between particles and the surfaces.  These surfaces contain hidden lengthscales capable of selectivity, pattern recognition, motion control, and adhesion of much larger objects, as shown in Fig. 2.

  
Fig. 2. Selectively nano-textured surface interacting with a 1 mm particle.

One key experimental finding is the existence of a threshold eature density below which particle adhesion does not occur, which forms the basis for selectivity.  At different nanotexture lengthscales on the sensor surface, however, particle rolling, slipping, and arrest are observed when micron-scale particles are subject to hydrodynamic forces in a shear flow.  Simulations have been developed to capture the complex dynamics arising from the coupling of hydrodynamic forces and torques to the heterogeneity of the nano-textured surfaces.  These simulations quantitatively uphold the experimental observation of threshold adhesion behavior and provide a detailed understanding of particle motion during dynamic adhesion.  Example particle trajectories are shown in Fig. 3.

Fig. 3.  Simulation results for (a) particle capture on 3 surfaces with
different patch densities (Q).  (b) Particle rolling, skipping, & slipping.

Selected Publications

Ranojoy D. Duffadar and Jeffrey M. Davis, "Interaction of micrometer-scale particles with nanotextured surfaces in shear flow," J. Colloid Interface Sci. 308, 20 (2007).

Ranojoy D. Duffadar and Jeffrey M. Davis, "Dynamics of micron-scale objects in low Reynolds number shear flow over nanotextured sensor surfaces," submitted (2006).

Naveen Tiwari and Jeffrey M. Daivs, "Selective dip-coating of a power-law fluid onto uniform and chemically heterogeneous surfaces," submitted (2006).

Naveen Tiwari and Jeffrey M. Davis, "Theoretical analysis of the effect of insoluble surfactant on the dip coating of chemically micropatterned surfaces," Phys. Fluids 18, 022102 (2006).

Jeffrey M. Davis, Dawn E. Kataoka, and Sandra M. Troian, "Transient dynamics and structure of optimal excitations in thermocapillary driven spreading: Precursor film model," Phys. Fluids 18, 092101 (2006).

Jeffrey M. Davis, "Asymptotic analysis of liquid films dip-coated onto chemically micropatterned surfaces," Phys. Fluids 17, 038101 (2005).

Jeffrey M. Davis and Sandra M. Troian, "Generalized linear stability of noninertial coating flows over topographical features," Phys. Fluids 17, 072103 (2005).

Anton A. Darhuber, Jian-Zhang Chen, Jeffrey M. Davis, and Sandra M. Troian, "A Study of Mixing in Thermocapillary Flows on Micropatterned Surfaces," Phil. Trans. R. Soc. Lond. A 362, 1037 (2004).

Jeffrey M. Davis and Sandra M. Troian, "Influence of boundary slip on the optimal excitations in thermocapillary-driven spreading," Phys. Rev. E 70, 046309 (2004). – also selected for Nov. 15, 2004 issue of Virtual Journal of Nanoscale Science & Technology.

Jeffrey M. Davis and Sandra M. Troian, "On a generalized approach to the linear stability of driven thin films," Phys. Fluids 15, 1344 (2003).

Jeffrey M. Davis and Sandra M. Troian, "Influence of attractive van der Waals interactions on the optimal excitations in thermocapillary-driven spreading," Phys. Rev. E 67, 016308 (2003).

Jeffrey M. Davis, Benjamin J. Fischer, and Sandra M. Troian, A General Approach to the Linear Stability of Thin Spreading Films, in "Interfacial Fluid Dynamics in Physico-Chemical Phenomena," Lecture Notes in Physics, edited by R. Narayanan, p. 79-105, Springer-Verlag (2003).

Anton A. Darhuber, Joseph P. Valentino, Jeffrey M. Davis, Sandra M. Troian, and Sigurd Wagner, "Fluidic actuation with addressable microheater arrays," Appl. Phys. Lett. 82, 657 (2003).

Anton A. Darhuber, Jeffrey M. Davis, Sandra M. Troian, and Walter W. Reisner, "Thermocapillary actuation of liquid flow on chemically patterned surfaces," Phys. Fluids 15, 1295 (2003).

Anton A. Darhuber, Jeffrey M. Davis, Walter. W. Reisner and Sandra. M. Troian, "Thermocapillary migration of liquids on patterned surfaces: Design concept for microfluidic delivery," in Micro Total Analysis Systems 2001, Kluwer Academic, J. M. Ramsey and A. van den Berg, editors, p 244 (2001).

Anton A. Darhuber, Sandra M. Troian, Jeffrey M. Davis, Scott M. Miller, and Sigurd Wagner, "Selective dip-coating of chemically micropatterned surfaces," J. Appl. Phys. 88, 5119 (2000).

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