Human skin is a remarkable organ. It consists of an integrated, stretchable network of sensors that relay information about tactile and thermal stimuli to the brain, allowing us to maneuver within our environment safely and effectively. Interest in large-area networks of electronic devices inspired by human skin is motivated by the promise of creating autonomous intelligent robots and biomimetic prosthetics, among other applications. The development of electronic networks comprised of flexible, stretchable, and robust devices that are compatible with large-area implementation and integrated with multiple functionalities is a testament to the progress in developing an electronic skin (e-skin) akin to human skin. E-skins are already capable of providing augmented performance over their organic counterpart, both in superior spatial resolution and thermal sensitivity. They could be further improved through the incorporation of additional functionalities (e.g., chemical and biological sensing) and desired properties (e.g., biodegradability and self-powering). Continued rapid progress in this area is promising for the development of a fully integrated e-skin in the near future.

25th Anniversary Article: The Evolution of Electronic Skin (E-Skin): A Brief History, Design Considerations, and Recent Progress

Dingcai Wu,*,† Fei Xu,† Bin Sun,† Ruowen Fu,† Hongkun He,‡ and Krzysztof Matyjaszewski*,‡ †Materials Science Institute, Key Laboratory for Polymeric Composite and Functional Materials of Ministry of Education, School of Chemistry and Chemical Engineering, Sun Yat-sen University, Guangzhou 510275, People's Republic of China ‡Department of Chemistry, Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, Pennsylvania 15213, United States

Design and Preparation of Porous Polymers

Recent advances in synthesis, physical properties and applications of conducting polymer nanotubes and nanofibers

Transfer printing represents a set of techniques for deterministic assembly of micro-and nanomaterials into spatially organized, functional arrangements with two and three-dimensional layouts. Such processes provide versatile routes not only to test structures and vehicles for scientific studies but also to high-performance, heterogeneously integrated functional systems, including those in flexible electronics, three-dimensional and/or curvilinear optoelectronics, and bio-integrated sensing and therapeutic devices. This article summarizes recent advances in a variety of transfer printing techniques, ranging from the mechanics and materials aspects that govern their operation to engineering features of their use in systems with varying levels of complexity. A concluding section presents perspectives on opportunities for basic and applied research, and on emerging use of these methods in high throughput, industrial-scale manufacturing.

Transfer Printing Techniques for Materials Assembly and Micro/Nanodevice Fabrication

Polyaniline nanostructures and the role of aniline oligomers in their formation

We report on the formation of ordered arrays of micrometric holes on the surface of polystyrene (PS) films cast from volatile solvents in the presence of humidity at different temperatures. The for...

Self-Organization of Polystyrenes into Ordered Microstructured Films and Their Replication by Soft Lithography

The adhesion of poly(dimethylsiloxane) (PDMS) rubber is largely improved by oxygen plasma surface treatment. The thickness of the silica-like surface layer is characterized by performing transmission electron microscopy imagery on microtome slices of welded plasma treated surfaces. The specific double layer contrast can be considered as equal to twice the thickness of the silica-like layer. The thickness measurements combined with strain-induced elastic buckling instability analysis gives an estimate of the elastic modulus of the silica-like layer equal to 1.5 GPa.

Thickness and Elastic Modulus of Plasma Treated PDMS Silica-like Surface Layer

Currently, there is a growing need for methods that can quantify and map the molecular interactions of biological samples, both with high-force sensitivity and high spatial resolution. Force-volume imaging is a valuable atomic force microscopy (AFM) modality for probing specific sites on biosurfaces. However, the low speed and poor spatial resolution of this method have severely hampered its widespread use in life science research. We use a novel AFM mode (i.e., peak force tapping with chemically functionalized tips) to probe the localization and interactions of chemical and biological sites on living cells at high speed and high resolution (8 min for 1 μm × 1 μm images at 512 pixels × 512 pixels). First, we demonstrate the ability of the method to quantify and image hydrophobic forces on organic surfaces and on microbial pathogens. Next, we detect single sensor proteins on yeast cells, and we unravel their mechanical properties in relation to cellular function. Owing to its key capabilities (quantitative mapping, resolution of a few nanometers, and true correlation with topography), this novel biochemically sensitive imaging technique is a powerful complement to other advanced AFM modes for quantitative, high-resolution bioimaging.

Sami Yunus

Papers

Self-Organization of Polystyrenes into Ordered Microstructured Films and Their Replication by Soft Lithography

Thickness and Elastic Modulus of Plasma Treated PDMS Silica-like Surface Layer

High-resolution imaging of chemical and biological sites on living cells using peak force tapping atomic force microscopy.

Giant stretchability of thin gold films on rough elastomeric substrates

Urea potentiometric enzymatic biosensor based on charged biopolymers and electrodeposited polyaniline