The mechanics of film-on-foil devices is presented in the context of thin-film transistors on steel and plastic foils. Provided the substrates are thin, such transistors function well after the foils are rolled to small radii of curvature. When a substrate with a lower elastic modulus is used, smaller radii of curvature can be achieved. Furthermore, when the transistors are placed in the neutral surface by sandwiching between a substrate and an encapsulation layer, even smaller radii of curvature can be attained. Transistor failure clearly shows when externally forced and thermally induced strains add to, or subtract from, each other

We have applied strain on thin-film transistors (TFTs) made of hydrogenated amorphous silicon on polyimide foil. In tension, the amorphous layers of the TFT fail by periodic cracks at a strain of ∼0.5%. In compression, the TFTs do not fail when strained by up to 2%, which is the highest value we can set controllably. The amorphous transistor materials can support such large strains because they lack a mechanism for dislocation motion. While the tensile driving force is sufficient to overcome the resistance to crack formation, the compressive failure mechanism of delamination is not activated because of the large delamination length required between transistor layers and polymer substrate

Organic electrochemical transistors (OECTs) are promising transducers for biointerfacing due to their high transconductance, biocompatibility, and availability in a variety of form factors. Most OECTs reported to date, however, utilize rather large channels, limiting the transistor performance and resulting in a low transistor density. This is typically a consequence of limitations associated with traditional fabrication methods and with 2D substrates. Here, the fabrication and characterization of OECTs with vertically stacked contacts, which overcome these limitations, is reported. The resulting vertical transistors exhibit a reduced footprint, increased intrinsic transconductance of up to 57 mS, and a geometry-normalized transconductance of 814 S m . The fabrication process is straightforward and compatible with sensitive organic materials, and allows exceptional control over the transistor channel length. This novel 3D fabrication method is particularly suited for applications where high density is needed, such as in implantable devices.

We evaluated amorphous silicon thin-film transistors (TFTs) fabricated on polyimide foil under uniaxial compressive or tensile strain. The strain was induced by bending or stretching. The on- current and hence the electron linear mobility µ depend on strain as µ = µ0(1 + 26E), where tensile strain has a positive sign and the strain is parallel to the TFT source-drain current path. Upon the application of compressive or tensile strain the mobility changes "instantly" and under compression then remains constant for up to 40 h. In tension, the TFTs fail mechanically at a strain of about +0.003 but recover if the strain is released "immediately.

We demonstrate the nonaqueous self-assembly of a low-molecular-mass organic gelator based on an electroactive p-type tetrathiafulvalene (TTF)-dipeptide bioconjugate. We show that a TTF moiety appended with diphenylalanine amide derivative (TTF-FF-NH2) self-assembles into one-dimensional nanofibers that further lead to the formation of self-supporting organogels in chloroform and ethyl acetate. Upon doping of the gels with electron acceptors (TCNQ/iodine vapor), stable two-component charge transfer gels are produced in chloroform and ethyl acetate. These gels are characterized by various spectroscopy (UV-vis-NIR, FTIR, and CD), microscopy (AFM and TEM), rheology, and cyclic voltammetry techniques. Furthermore, conductivity measurements performed on TTF-FF-NH2 xerogel nanofiber networks formed between gold electrodes on a glass surface indicate that these nanofibers show a remarkable enhancement in the conductivity after doping with TCNQ.