All-Solution-Processed Electronics with Sub-Microscale Resolution and Nanoscale Fidelity Fabricated Via a Humidity-Controlled, Surface Energy-Directed Assembly Process.

Solution-based processes have received considerable attention in the fabrication of electronics and sensors owing to their merits of being low-cost, vacuum-free, and simple in equipment. However, the current solution-based processes either lack patterning capability or have low resolution (tens of micrometers) and low pattern fidelity in terms of line edge roughness (LER, several micrometers). Here, we present a surface energy-directed assembly (SEDA) process to fabricate metal oxide patterns with up to 2 orders of magnitude improvement in resolution (800 nm) and LER (16 nm).

Fabrication of Flexible and Transparent Metal Mesh Electrodes Using Surface Energy-Directed Assembly Process for Touch Screen Panels and Heaters.

Transparent conductive electrodes (TCEs) are indispensable components of various optoelectronic devices such as displays, touch screen panels, solar cells, and smart windows. To date, the fabrication processes for metal mesh-based TCEs are either costly or having limited resolution and throughput. Here, a two-step surface energy-directed assembly (SEDA) process to efficiently fabricate high resolution silver meshes is introduced.

Directed Assembly of Nanomaterials for Making Nanoscale Devices and Structures: Mechanisms and Applications.

Nanofabrication has been utilized to manufacture one-, two-, and three-dimensional functional nanostructures for applications such as electronics, sensors, and photonic devices. Although conventional silicon-based nanofabrication (top-down approach) has developed into a technique with extremely high precision and integration density, nanofabrication based on directed assembly (bottom-up approach) is attracting more interest recently owing to its low cost and the advantages of additive manufacturing. Directed assembly is a process that utilizes external fields to directly interact with nanoelements (nanoparticles, 2D nanomaterials, nanotubes, nanowires, etc.

High-Rate Printing of Micro/Nanoscale Patterns Using Interfacial Convective Assembly.

Printing of electronics has been receiving increasing attention from academia and industry over the recent years. However, commonly used printing techniques have limited resolution of micro- or sub-microscale. Here, a directed-assembly-based printing technique, interfacial convective assembly, is reported, which utilizes a substrate-heating-induced solutal Marangoni convective flow to drive particles toward patterned substrates and then uses van der Waals interactions as well as geometrical confinement to trap the particles in the pattern areas.

Solution-processed organic field-effect transistors using directed assembled carbon nanotubes and 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT).

Achieving low-cost fabrication of organic field-effect transistors (OFETs) has long been pursued in the semiconductor industry. Solution-based process allows the fabrication of OFETs cost-effective because of its merit of vacuum-free and room temperature operation. Here, we show a facile and scalable fabrication of solution-processed OFETs using carbon nanotube (CNT) as source/drain electrodes and 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT) as semiconducting layer on silicon as well as on flexible and transparent polyethylene terephthalate (PET) substrates.

Assembly of Highly Aligned Carbon Nanotubes Using an Electro-Fluidic Assembly Process.

Carbon nanotubes (CNTs) are promising building blocks for emerging wearable electronics and sensors due to their outstanding electrical and mechanical properties. However, the practical applications of the CNTs face challenges of efficiently and precisely placing them at the desired location with controlled orientation and density. Here, we introduce an electro-fluidic assembly process to assemble highly aligned and densely packed CNTs selectively on a substrate with patterned wetted areas at a high rate.

Measuring Bone Biomarker Alkaline Phosphatase with Wafer-Scale Nanowell Array Electrodes.

Biosensors that can analyze a single drop of biological fluid can overcome limitations such as extraction volume from humans or animals, ethical problems, time, and cost. In this work, we have developed a highly sensitive electrochemical (EC) biosensor based on a nanowell array (NWA) for the detection of alkaline phosphatase (ALP), a serum indicator of bone formation. The size of the electrode is 2 × 1 mm and has over 10 million nanowells (400 nm diameter) arranged uniformly on the electrode surface.

Scalable Directed Assembly of Highly Crystalline 2,7-Dioctyl[1]benzothieno[3,2- b][1]benzothiophene (C8-BTBT) Films.

Assembly of organic semiconductors with ordered crystal structure has been actively pursued for electronics applications such as organic field-effect transistors (OFETs). Among various film deposition methods, solution-based film growth from small molecule semiconductors is preferable because of its low material and energy consumption, low cost, and scalability. Here, we show scalable and controllable directed assembly of highly crystalline 2,7-dioctyl[1]benzothieno[3,2- b][1]benzothiophene (C8-BTBT) films via a dip-coating process.

Directed assembly-based printing of homogeneous and hybrid nanorods using dielectrophoresis.

Printing nano and microscale three-dimensional (3D) structures using directed assembly of nanoparticles has many potential applications in electronics, photonics and biotechnology. This paper presents a reproducible and scalable 3D dielectrophoresis assembly process for printing homogeneous silica and hybrid silica/gold nanorods from silica and gold nanoparticles. The nanoparticles are assembled into patterned vias under a dielectrophoretic force generated by an alternating current (AC) field, and then completely fused in situ to form nanorods.

Polypyrrole Films with Micro/Nanosphere Shapes for Electrodes of High-Performance Supercapacitors.

We demonstrate a simple and efficient one-step procedure for synthesizing a solid state polypyrrole (PPy) thin film for supercapacitor applications using alternating current impedance spectroscopy. By controlling the frequency and amplitude we were able to create unique PPy nano/microstructures with a particular morphology of the loop. Our PPy micro/nanosphere shows extremely high capacitance of 568 F/g, which is close to the theoretical value of 620 F/g and 20-100% higher than that of other reported PPy electrodes.

High-Rate Assembly of Nanomaterials on Insulating Surfaces Using Electro-Fluidic Directed Assembly.

Conductive or semiconducting nanomaterials-based applications such as electronics and sensors often require direct placement of such nanomaterials on insulating surfaces. Most fluidic-based directed assembly techniques on insulating surfaces utilize capillary force and evaporation but are diffusion limited and slow. Electrophoretic-based assembly, on the other hand, is fast but can only be utilized for assembly on a conductive surface.

Novel Nanoprinting for Oral Delivery of Poorly Soluble Drugs.

Many of the newly developed drugs for cancer, and some of those for cardiovascular disease, are poorly soluble in water and cannot be taken orally. This can be overcome by employing a new and effective delivery system utilizing nanotechnology. We present a new method for oral preparation of poorly soluble drugs that entails assembling (printing) drug-loaded polymeric micelles into sub-100 nm orally acceptable nanorods (NRs).

High-rate nanoscale offset printing process using directed assembly and transfer of nanomaterials.

High-rate nanoscale offset printing using a newly developed reusable template enables the assembly of nanomaterials into nanostructures followed by their transfer onto a flexible substrate in a few minutes. The developed template can potentially be reused more than 100 times in the offset printing process without any additional functionalization. This approach provides a new way for the printing of flexible devices with nanoscale patterns.

Life cycle impacts and benefits of a carbon nanotube-enabled chemical gas sensor.

As for any emerging technology, it is critical to assess potential life cycle impacts prior to widespread adoption to prevent future unintended consequences. The subject of this life cycle study is a carbon nanotube-enabled chemical gas sensor, which is a highly complex, low nanomaterial-concentration application with the potential to impart significant human health benefits upon implementation. Thus, the net lifecycle trade-offs are quantified using an impact-benefit ratio (IBR) approach proposed herein, where an IBR < 1 indicates that the downstream benefits outweigh the upstream impacts.

Three-dimensional crystalline and homogeneous metallic nanostructures using directed assembly of nanoparticles.

Directed assembly of nano building blocks offers a versatile route to the creation of complex nanostructures with unique properties. Bottom-up directed assembly of nanoparticles have been considered as one of the best approaches to fabricate such functional and novel nanostructures. However, there is a dearth of studies on making crystalline, solid, and homogeneous nanostructures.

3-D perpendicular assembly of single walled carbon nanotubes for complimentary metal oxide semiconductor interconnects.

Due to their superior electrical properties such as high current density and ballistic transport, carbon nanotubes (CNT) are considered as a potential candidate for future Very Large Scale Integration (VLSI) interconnects. However, direct incorporation of CNTs into Complimentary Metal Oxide Semiconductor (CMOS) architecture by conventional chemical vapor deposition (CVD) growth method is problematic since it requires high temperatures that might damage insulators and doped semiconductors in the underlying CMOS circuits. In this paper, we present a directed assembly method to assemble aligned CNTs into pre-patterned vias and perpendicular to the substrate.

Acceleration of poly(L-lactide) degradation by TiO2 nanoparticles in sunlight.

Poly(L-lactide) (PLA) is known to eventually be degraded into water and carbon dioxide by the microorganisms of the natural world. Titanium dioxide (TiO2) has been used in the biomedical and bioengineering fields as a photocatalyst. The purpose of this research project is to evaluate the influence of TiO2 added to PLA films both before and after irradiation of the films with sunlight.

High-performance H(2)S detection by redox reactions in semiconducting carbon nanotube-based devices.

Here we report the highly effective detection of hydrogen sulfide (H2S) gas by redox reactions based on single-walled carbon nanotubes (SWCNTs) functionalized with 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) as a catalyst and we also discuss the important role of water vapor in the electrical conductivity of SWCNTs during the sensing of H2S molecules. To explore the H2S sensing mechanism, we investigate the adsorption properties of H2S on carbon nanotubes (CNTs) and the effects of the TEMPO functionalization using first-principles density functional theory (DFT) and we summarize current changes of devices resulting from the redox reactions in the presence of H2S. The semiconducting-SWCNT (s-SWCNT) device functionalized with TEMPO shows a very high sensitivity of 420% at 60% humidity, which is 17 times higher than a bare s-SWCNT device under dry conditions.

Wafer-scale nanowell array patterning based electrochemical impedimetric immunosensor.

We have reported that nanowell array (NWA) can enhance electrochemical detection of molecular binding events by controlling the binding sites of the captured molecules. Using NWA biosensor based amperometric analysis, we have detected biological macromolecules such as DNA, protein or aptamers at low concentrations. In this research, we developed an impedimetric immunosensor based on wafer-scale NWA for electrochemical detection of stress-induced-phosphoprotein-1 (STIP-1).

Phospholipase-catalyzed hydrolysis in an artificial cell membrane in the presence of melittin.

Biomimicry involves the use of the structure and function of biological systems as models for the design and engineering of materials and machines. An artificial cell membrane was developed using biomembrane components, and the membrane, formed by a lipid bilayer, was analyzed using surface plasmon resonance (SPR) to monitor hydrolysis by phospholipase (PL). The simultaneous atomic force microscope (AFM) images show that PL catalyzed the nanometer-scale hydrolysis of the artificial lipid biomembranes through enzymatic hydrolysis.

Detection of single nucleotide polymorphisms using a biosensor-containing titanium-well array.

The rapid identification and verification of single nucleotide polymorphisms (SNPs) were demonstrated using a well array sensor containing anti-biofouling titanium (Ti). Probe single-stranded DNA (ssDNA) was immobilized inside a titanium-well array on amine-modified glass surfaces with anti-biofouling behavior via a streptavidin-biotin interaction. Fluorescence intensity changes originating from the hybridization of nucleic acids to protein-bound nucleic acids linked to Alexa Fluor (FL) 647 were observed.

Highly sensitive microscale in vivo sensor enabled by electrophoretic assembly of nanoparticles for multiple biomarker detection.

This paper describes a microscale in vivo sensor platform device for the simultaneous detection of multiple biomarkers. We designed the polymer-based biosensors incorporating multiple active isolated areas, as small as 70 μm × 70 μm, for antigen detection. The fabrication approach involved conventional micro- and nano-fabrication processes followed by site-specific electrophoretic directed assembly of antibody-functionalized nanoparticles.

A molybdenum disulfide/carbon nanotube heterogeneous complementary inverter.

We report a simple, bottom-up/top-down approach for integrating drastically different nanoscale building blocks to form a heterogeneous complementary inverter circuit based on layered molybdenum disulfide and carbon nanotube (CNT) bundles. The fabricated CNT/MoS(2) inverter is composed of n-type molybdenum disulfide (MOS(2)) and p-type CNT transistors, with a high voltage gain of 1.3.

Modulating the performance of carbon nanotube field-effect transistors via Rose Bengal molecular doping.

A simple, reliable, and large scale ambient environment doping method for carbon nanotubes is a highly desirable approach for modulating the performance of nanotube based electronics. One of the major challenges is doping carbon nanotubes to simultaneously offer a large shift in threshold voltage and an improved subthreshold swing. In this paper, we report on modulating the performance of carbon nanotube field-effect transistors (CNTFETs) by rationally selecting doping molecules.

Size-selective template-assisted electrophoretic assembly of nanoparticles for biosensing applications.

The precise, size-selective assembly of nanoparticles gives rise to many applications where the assembly of nano building blocks with different biological or chemical functionalizations is necessary. We introduce a simple, fast, reproducible-directed assembly technique that enables a complete sorting of nanoparticles with single-particle resolution. Nanoparticles are size-selectively assembled into prefabricated via arrays using a sequential template-directed electrophoretic assembly method.