Advanced manufacturing strategies have enabled large-scale, economical, and efficient production of electronic components that are an integral part of various consumer products ranging from simple toys to intricate computing systems; however, the circuitry for these components is (by and large) produced via top-down lithography and is thus limited to planar surfaces. The present work demonstrates the use of reconfigurable soft microreactors for the patterned deposition of conductive copper traces on flat and embossed two-dimensional (2D) substrates as well as nonplanar substrates made from different commodity plastics. Using localized, flow-assisted, low-temperature, electroless copper deposition, conductive metallic traces are fabricated, which, when combined with various off-the-shelf electronic components, enabled the production of simple circuits and antennas with unique form factors. This solution-phase approach to the patterned deposition of functional inorganic materials selectively on different polymeric components will provide relatively simple, inexpensive processing opportunities for the fabrication of 2D/nonplanar devices when compared to complicated manufacturing methods such as laser-directed structuring. Further, this approach to the patterned metallization of different commodity plastics offers unique design opportunities applicable to the fabrication of planar and nonplanar electronic and interconnect devices, and other free-form electronics with less structural "bloat" and weight (by directly coating support elements with circuitry).

Silicone elastomers are used in a variety of “stretchable” technologies (e.g., wearable electronics and soft robotics) that require the elastomeric components to accommodate varying magnitudes of mechanical stress during operation; however, there is limited understanding of how mechanical stress influences the surface chemistry of these elastomeric components despite the potential importance of this property with regards to overall function. In this study, plasma-oxidized silicone (poly­(dimethylsiloxane)) films were systematically subjected to various amounts of tensile stress and the resulting surface chemical changes were monitored using contact angle measurements, X-ray photoelectron spectroscopy, and gas chromatography–mass spectrometry. Understanding the influence of mechanical stress on these materials made possible the development of a facile method for the rapid, on-demand switching of surface wettability and the generation of surface wettability patterns and gradients. The use of mechanical stress to control surface wettability is broadly applicable to the fields of microfluidics, soft robotics, printing, and to the design of adaptable materials and sensors.

The working principle of large-area, open-gate field effect transistors (ogFETs) is attractive for the high-sensitivity detection of chemicals and interfacing with single cells. We describe an ogFET composed of a self-assembled, two-dimensional (2D) random network of 1D chains of 10 nm Au particles spanning over 25 μm. The device has a gating gain of 103-fold at room temperature (RT) compared to <50% for reported nanoparticle arrays at RT. The current, I ∼ (V – V T)ζ, is functionally identical to the Coulomb blockade (CB) effect observed at cryogenic temperatures, and the conductance gap, V T, at room temperature cannot be attributed to local charging for large particles (>5 nm). Surprisingly, unlike the effect observed in CB, the V T remains invariant over a large gating potential 0–25 V, leading to a universal behavior where all the I–V curves collapse into a single master curve. We explain the universality as a classical critical behavior by quantitatively mapping the percolation path in real-space images. The paths evolve as self-similar percolation channels in a fractal dimension of 1.88. The device principle enables a 103-fold gating gain in all-metallic nanoparticle arrays at RT and will potentially lead to ogFET sensors and electrochemical devices with liquid-gate junctions. The critical behavior with bias may serve as a model system to study the electronic transport in these exotic systems.

Microfluidic channels are typically fabricated in polydimethylsiloxane (PDMS) using soft lithography and sealed against a support substrate using various irreversible/reversible techniques-the most widely used method is the irreversible bonding of PDMS to glass using oxygen plasma. These techniques are limited in their ability to seal channels against rough, uneven, and/or three-dimensional substrates. This manuscript describes the design and fabrication of soft microfluidic systems from combinations of silicone elastomers that can be reversibly sealed against an array of materials of various topographies/geometries using compression. These soft systems have channels with cross-sectional dimensions that can be decreased, reversibly, by hundreds of microns using compressive stress, and the ability to interface with virtually any support substrate. These capabilities go beyond that achievable with devices fabricated in PDMS alone and enable the integration of microfluidic functionality directly with rough and/or 3D surfaces, providing new opportunities in solution processing useful to, for example, materials science and the analytical/forensic sciences.