Micro and Nanosystems - Volume 2, Issue 1, 2010

A dedicated printed electronics technology platform has been developed and implemented. The technology is devoted to the manufacturing of all-organic transistor devices with sub-micron feature size as multilayered structures, obtained through a sequential combination of deposition from solution and patterning steps through stamps. The manufacturing process includes fabrication of both rigid and flexible elastomeric stamps that are used in the development of fully printed devices and circuits on glass and plastic substrates. Moreover, to test the performance of printed electronic devices, a new compact simulation model has been developed taking into account the effect of contact resistance. Such a parameter acts as a key engineering parameter to enable access of polymer-based printed electronics to logic circuits running at relatively high speed, eventually associated with design solutions that allow achieving full rail-to-rail speed-up logic circuits and low power dissipation.

Electronics packaging must be designed to meet the increasing requirements of the microelectronics industry. Future packages will have an even higher number of I/O's and pitches down to 20 microns resulting in high dissipation losses and extreme current densities. When using conventional materials, design engineers will face physical barriers and limitations in performance and new material solutions have to be found. Reliable interconnects are a major concern of packaging technologies. The steadily increasing mechanical, thermal and electrical loadings open up new areas of research. One way to solve the problems of future electronics is the use of nanotechnologies and nanomaterials. Among the world's most researched materials are carbon nanotubes (CNTs) [1-5]. CNTs have excellent thermal, electrical and mechanical properties. They can be used in various ways. One researched field of application are CNT-polymer composites which combine common technologies with advanced materials. This paper focuses on the latest results obtained for CNT-filled adhesives for electronics packaging and compares the new materials with conventional, electrical Ag-filled conductive adhesives. Based on previous investigations on CNT-epoxy composites [1-4], a comprehensive study of the mechanical, electrical and thermal properties of selected promising candidates was conducted. Additionally, the performance of the novel composites as conductive adhesives in electronics packages was included in the evaluation.

In this paper, the design and simulation of a dual-mode Aluminum MEMS micromirror device are proposed. The dual-mode micromirror can work in either torsional or piston modes, depending on the voltage scheme applied to the bottom driving electrodes. The working principle and performance of the micromirror are analyzed. Based upon the analysis, a set of optimized micromirror design parameters is suggested, and the corresponding performance of the micromirror design is reported. According to the analysis, the mirror can deflect for a maximum controllable displacement of 1.3μm in its piston mode, and rotate for a maximum controllable angle of ±3.6° in its torsional mode. If the micromirror works in digital operation in its torisional mode, a maximum rotation angle of ±7.8° can be achieved. ANSYS FEM method is used to simulate the first five vibrational modes and the corresponding resonant frequencies of the micromirror. The micromirror is to be fabricated with thick photoresist sacrificial layer technique. The proposed micromirror can be used to modulate the phase as well as the direction of the incident light due to its dual-mode modes.

The characterization of individual nanoscale objects such as carbon nanotubes (CNTs) is one of the main challenges in material science and nanotechnology. In this paper, we present a nanorobotic strategy allowing the nondestructive mechanical characterization of individual CNTs. A nanorobotic setup is developed to perform elastic deformations of multiwalled carbon nanotubes (MWCNTs). Characteristic force/displacement curves are measured and used to calculate the Young's modulus. Transmission electron microscope (TEM) images of the given CNTs show an additional conical layer of amorphous carbon enclosing the real multiwalled structure. Thus, different theoretical models are examined aiming to find the proper mechanical description of the analyzed CNTs. The experimental results show a significant influence of the outer carbon layer on the whole mechanical behavior of the MWCNTs.

The effects of DWCNTs and MWCNTs on primary immune cells in vitro were studied at cell level. The results indicated that DWCNTs (1, 10, 25, and 50μg/mL) promoted the proliferation of the spleen cells. MWCNTs had no significant effect on the proliferation of the spleen cells at concentrations of 1, 10, and 10μg/mL, but promoted the proliferation at concentration of 25μg/mL. DWCNTs (1, 10 25, and 50μg/mL) promoted the proliferation of T lymphoid cells stimulated by ConA, MWCNTs (1 and 10μg/mL) also promoted the proliferation of T lymphoid cells stimulated by ConA, but had no significant effect on the proliferation of T lymphoid cells stimulated by ConA at concentrations of 25 and 50μg/mL. DWCNTs and MWCNTs promoted the proliferation of B lymphoid cells stimulated by LPS at concentrations of 10, 25, and 50μg/mL, but had no significant effect on the proliferation of B lymphoid cells stimulated by LPS at concentration of of 1μg/mL. DWCNTs significantly promoted NK cell activity at concentrations of 1 and 10μg/mL, but turned to inhibit NK cell activity at concentrations of 25 and 50μg/mL. MWCNTs significantly promoted NK cell activity at concentration of 1μg/mL, then had no effect NK cell activity at concentration of 10μg/mL, but turned to inhibit NK cell activity at concentrations of 25 and 50μg/mL. The results suggest that the effects of CNTs on primary immune cells in vitro depend on their species and size, moreover, they are pivotal factors for switching the biological effects of CNTs from toxicity to activity, from damage to protection, or from down-regulation to up-regulation.

A sensitivity deviation probability model is proposed, for the first time, to describe the sensitivity deviation probability of micro-accelerometer brought by the MEMS process error in comb finger gaps. The sensitivity model is set up following the capacitance probability model on the premise that the error is in an interval with equal probability. It's indicated that, by the model, the probabilities for two kinds of deviation, decreasing and increasing, are different with the same process error degree. When the process error is about 25%, the sensitivity will decrease 5-10% with 40-50% probability, and increase 5-10% with 25-30% probability. Meanwhile, when the comb finger's number n is small, the deviation probability is big. When n is less than 20, the sensitivity decreases 10% with about 30% probability, but when n is close to 50∼60, the probability deceases to about 10%. Furthermore, the model is helpful in research and development field of MEMS accelerometers.

The fluoropolymer/silicon sol composites were fabricated via conventional materials by using surface gelation technology; the hydrophobic models in the surfaces of the composite coatings were discussed. The wetting behavior of the composite coating surface exhibited Wenzel model when the surface's roughness was low enough, and Cassie model was available when roughness was high enough. It was assumed that the hierarchical structures of the composite coating agreed with the fractal structures described by Koch curve. Based on the fractal structure equation, the super-hydrophobic fractal structure model of the composite coating was constructed, the simulation agreed with the experimental data well.