Stretchable Chemical Patterns for the Assembly and Manipulation of Arrays of Microdroplets with Lensing and Micromixing Functionality

Abstract

The chemical properties of a surface are readily controlled using a layer (or layers) of surface‐functional groups that can be generated with, for example, self‐assembled monolayers (SAMs) or polymer brushes. These methods have enabled rational control over surface chemistry, which directly impacts surface properties, such as wettability, but generally follow a serial approach to building up surface‐functional groups (i.e., separate chemical steps are needed for the initial and each subsequent surface modification). This paper describes systems based on soft materials—stretchable chemical patterns—that have surface properties that are easily and reversibly modified using mechanical deformations. These systems couple surface‐chemical features such as the density and arrangement of functional groups on elastomeric polymers (e.g., polydimethylsiloxane) to mechanically induced surface deformations. This approach enables rapid and reversible control of surface chemistry and thus surface properties and processes. The behavior of these systems is characterized using fluorescent molecules and their utility illustrated through the organization and manipulation of arrays of micrometer‐scale droplets, which have optical and small‐volume mixing functionalities applicable to microlens and microreactor technologies, respectively. The capabilities of these systems may be extended to, for example, the control of heterogeneous nucleation, surface reactivity, and micro/nanoscale assembly.