Chih-Ting Lin

Inkjet-Printed Organic Field-Effect Transistor by Using Composite Semiconductor Material of Carbon Nanoparticles and Poly(3-Hexylthiophene)

Poly(3-hexylthiophene), P3HT, has been widely used in organic electronics as a semiconductor material. It suffers from the low carrier mobility characteristics. This limits P3HT to be employed in applications. Therefore, the blending semiconductor material, carbon nanoparticle (CNP), and P3HT, are developed and examined by inkjet-printing organic field-effect transistor technology in this work. The effective carrier mobility of fabricated OFETs can be enhanced by 8 folds with adding CNP and using O2 plasma treatment. At the same time, the transconductance of fabricated OFETs is also raised by 5 folds. Based on the observations of SEM, XRD, and FTIR, these improvements are contributed to the local field induced by the formation of CNP/P3HT complexes. This observation presents an insight of the development in organic semiconductor materials. Moreover, this work also offers a low-cost and effective semiconductor material for inkjet-printing technology in the development of organic electronics.

A Room-Temperature Operation Formaldehyde Sensing Material Printed Using Blends of Reduced Graphene Oxide and Poly(methyl methacrylate)

This work demonstrates a printable blending material, i.e., reduced graphene oxide (RGO) mixed with poly(methyl methacrylate) (PMMA), for formaldehyde sensing. Based on experimental results, 2% RGO/10% PMMA is an optimal ratio for formaldehyde detection, which produced a 30.5% resistance variation in response to 1000 ppm formaldehyde and high selectivity compared to different volatile organic compounds (VOCs), humidity, CO, and NO. The demonstrated detection limit is 100 ppm with 1.51% resistance variation. Characterization of the developed formaldehyde sensing material was performed by Fourier-transform infrared (FTIR) spectrometry, scanning electron microscopy (SEM), and Raman spectroscopy. Based on Raman spectroscopy, the basic sensing mechanism is the band distortion of RGO due to blending with PMMA and the adsorption of formaldehyde. This work establishes insights into the formaldehyde sensing mechanism and explores a potential printable sensing material for diverse applications.

A Low-Power Integrated Humidity CMOS Sensor by Printing-on-Chip Technology

A low-power, wide-dynamic-range integrated humidity sensing chip is implemented using a printable polymer sensing material with an on-chip pulse-width-modulation interface circuit. By using the inkjet printing technique, poly(3,4-ethylene-dioxythiophene)/polystyrene sulfonate that has humidity sensing features can be printed onto the top metal layer of a 0.35 μm CMOS IC. The developed printing-on-chip humidity sensor achieves a heterogeneous three dimensional sensor system-on-chip architecture. The humidity sensing of the implemented printing-on-chip sensor system is experimentally tested. The sensor shows a sensitivity of 0.98% to humidity in the atmosphere. The maximum dynamic range of the readout circuit is 9.8 MΩ, which can be further tuned by the frequency of input signal to fit the requirement of the resistance of printed sensor. The power consumption keeps only 154 μW. This printing-on-chip sensor provides a practical solution to fulfill an ultra-small integrated sensor for the applications in miniaturized sensing systems.

Wear and Corrosion Investigation on the Electrodeposited Ni-P Coating

The wear and corrosion characteristics of an electrodeposited Ni-P coating were studied using a block-on-ring wear tester. The testing environments included dry wear and immersion wear in a 5 wt% NaCl water solution bath to simulate the corrosive atmosphere. The wear behavior is discussed in terms of the friction coefficient, wear rate, and surface roughness. Under boundary lubrication, the wear mechanism changed from both adhesive and abrasive wear for dry contact to mostly abrasive wear in corrosive salt water. The corrosion pits and corrosion film formed during accelerated corrosion wear testing not only lowered the friction coefficient but decreased the surface roughness. However, due to the accelerated pitting corrosion and removal of the corrosion film, the weight loss was slightly increased. Finally, the X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) analyses confirmed the formation of a porous corrosion film after the wear test in salt water.

Self-Sustain Wireless Sensor Module

A Solar-Powered Sensor Module (SPSM) that uses low-cost capacitors as energy buffers to power wireless sensor motes was investigated. Compared to batteries or super capacitors, SPSM is particularly suitable for light-weight tasks since it buffers limited energy and powers up periodically. With our method, the energy charging time can be shortened to about 100 ms for a maximum power point tracking component, and the current of the output regulator can reach 71% efficiency.

Percolation of Carbon Nanoparticles in Poly(3-Hexylthiophene) Enhancing Carrier Mobility in Organic Thin Film Transistors

To improve the field-effect mobility of all-inkjet-printed organic thin film transistors (OTFTs), a composite material consisted of carbon nanoparticles (CNPs) and poly(3-hexylthiophene) (P3HT) was reported by using homemade inkjet-printing system. These all-inkjet-printed composite OTFTs represented superior characteristics compared to the all-inkjet-printed pristine P3HT OTFTs. To investigate the enhancement mechanism of the blended materials, the percolation model was established and experimentally verified to illustrate the enhancement of the electrical properties with different blending concentrations. In addition, experimental results of OTFT contact resistances showed that both contact resistance and channel resistance were halved. At the same time, X-ray diffraction measurements, Fourier transform infrared spectra, ultraviolet-visible light, and photoluminescence spectra were also accomplished to clarify the material blending effects. Therefore, this study demonstrates the potential and guideline of carbon-based nanocomposite materials in all-inkjet-printed organic electronics.