Single-walled carbon nanotube (SWNT) has gained significant interest as a transducer in various electrochemical sensing devices due to their unique structure, compatibility with biomolecules, and excellent electronic properties. As-prepared SWNTs are usually a mixture of semiconducting and metallic ones. Despite of the higher content of semiconducting components in mixed SWNTs, metallic properties are predominantly expressed due to the bundling issue of the SWNT during the fabrication process, limiting the applicability to bio-transistor application. Here, we present a multi-scale semiconducting electronic film of SWNTs as a transducing platform for electrochemical field-effect-transistor (eFET) suitable for the sensitive detection of subtle biological modulation. A genetically engineered filamentous M13 phage showing strong binding affinity toward SWNTs on its body surface was used as a biological material, allowing us to fabricate a large-scale transparent semiconducting nanocomposite. As the relative ratio of SWNT to M13 phage decreases, the on–off ratio of SWNT electronic film increases by 1200%. To show broad applicability, the multi-scale SWNT nanomesh-based eFET is applied for monitoring a variety of biological reactions in association with enzymes, aptamers, and even cyanobacteria. The biomimetic electronic material system with the capability of transducing biological responses at a large scale over a broad dynamic range holds excellent promise for biosensors, biofuel cells, and environment monitoring.

Controlling the stick and slip motions of the contact lines in a confined geometry comprised of a spherical lens with a flat substrate is useful for manufacturing polymer ring patterns. We used a sphere on a flat geometry, by which we could control the interfaces of the solution, vapor and substrate. By this method, hundreds of concentric ring-pattern formations of a linear conjugated polymer, poly [2-methoxy-5-(2-thylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV), were generated with excellent regularity over large areas after complete solvent evaporation. Subsequently, the MEH-PPV ring patterns played a role as a directed template to organize highly regular concentric rings of single-walled carbon nanotubes(SWCNTs); when a droplet of the SWCNT suspension in water was casted onto the prepared substrate, hydrophobic polymer patterns confined the water dispersed SWCNTs in between the hydrophilicized SiO2/Si substrate. As the solvent evaporated, SWCNT-rings were formed in between MEH-PPV rings with controlled density. Finally, we used a lift-off process to produce SWCNT patterns by the removal of a sacrificial polymer template with organic solvent. We also fabricated a field effect transistor using self-assembled SWCNT networks on a SiO2/Si substrate.

The bio-organic thin film transistor (BiOTFT) with the DNA and DNA-surfactant complex as a dielectric layer shows memory function. In order to investigate the effect of surfactant structure on the OTFT memory device performance, different kinds of surfactant were introduced. The octadecyltrimethylammonium chloride (OTMA), ctyltrimethylammonium chloride (CTMA), or lauroylcholine chloride (Lau) as cationic surfactant as mixed with DNA to prepare the DNA complex through the electrostatic interaction. In addition, the different molecular weight DNA also has been studied to analyze the effect of DNA chain length on the performance of the physical property. Many kinds of methods including UV-vis, Circular dichiroism (CD), I-V characteristic and atomic force microscope (AFM) have been applied to analyze the property of DNA complex. In conclusion, all of DNA complex with CTMA, OTMA and Lau revealed to work as the bio-organic thin film transistor memory, and the device fabricated by Lau has the highest ON current and showed better device performance.

Currently, graphene is a topic of very active research in fields from science to potential applications. For various radio-frequency (RF) circuit applications including low-noise amplifiers, the unique ambipolar nature of graphene field-effect transistors can be utilized for high-performance frequency multipliers, mixers and high-speed radiometers. Potential integration of graphene on Silicon substrates with complementary metal-oxide-semiconductor compatibility would also benefit future RF systems. The future success of the RF circuit applications depends on vertical and lateral scaling of graphene metal-oxide-semiconductor field-effect transistors to minimize parasitics and improve gate modulation efficiency in the channel. In this paper, we highlight recent progress in graphene materials, devices, and circuits for RF applications. For passive RF applications, we show its transparent electromagnetic shielding in Ku-band and transparent antenna, where its success depends on quality of materials. We also attempt to discuss future applications and challenges of graphene.

Si Nanowire (NW) field effect transistors (FETs) were fabricated on hard Si and flexible polyimide (PI) substrates, and their electrical characteristics were compared. Si NWs used as channels were synthesized by electroless etching method at low temperature, and these NWs were refined using a centrifugation method to get the NWs to have an optimal diameter and length for FETs. The gate insulator was poly(4-vinylphenol) (PVP), prepared using a spin-coating method on the PI substrate. Gold was used as electrodes whose gap was 8 μm. These gold electrodes were deposited using a thermal evaporator. Current-voltage (I-V) characteristics of the device were measured using a semiconductor analyzer, HP-4145B. The electrical properties of the device were characterized through hole mobility, Ion/Ioff ratio and threshold voltage. The results showed that the electrical properties of the TFTs on PVP were similar to those of TFTs on SiO2. The bending durability of SiNWs TFTs on PI substrate was also studied with increasing bending times. The results showed that the electrical properties were maintained until the sample was folded about 500 times. But, after more than 1000 bending tests, drain current showed a rapid decrease due to the defects caused by the roughness of the surface of the Si NWs and mismatches of the Si NWs with electrodes.