This PDF file contains the editorial “Editorial: Mourning the loss of Prof. Franco Cerrina” for JM3 Vol. 9 Issue 03

This PDF file contains the editorial “Special Section Guest Editorial: BioMEMS, Theory and Practice of MEMS/NEMS, and Sensors” for JM3 Vol. 9 Issue 03

We prepare various polymer-based microstructures for gold colloid detection in a Raman system. Several surface treatment techniques as well as chip configurations are discussed with an emphasis on their strengths and limitations. First, the optimum focus space is found for the experiment. Next, surface treatment effects for the Raman signal on the polymer-based substrate are compared. Finally, the Raman intensity of three channel configurations is compared along the cross sectional direction. There results demonstrate that a triangle shape provides the highest intensity for the same microstructure depth. A signal-enhanced mechanism on the difference cross sectional surface is also discussed in this research. Optimal shape designs based on polymer-based configurations are proposed for Raman detection in microchannels. This can give rise to several interesting applications, including trapping viruses from samples, and enzymatic reaction from enzymatic immuno-assay systems for real-time monitoring.

Steady-state and nanosecond time-resolved spectroscopies are performed to investigate the interaction between CdSe quantum dots (QDs) and mesotetraphenylporphyrin (TPP) photosensitizers under two-photon excitation with 800-nm femtosecond laser pulses. The luminescent intensity and lifetime of the QDs decrease intensively in the QD-porphyrin mixture, whereas those of the TPP increase, suggesting occurence of a nonradiative fluorescence resonance energy transfer (FRET) process between the excited states of the donors and acceptors. An energy transfer efficiency of 0.27 is estimated from quenching of the excited-state radiative lifetime of the QDs. A 4-nm red shift in the emission spectrum of the CdSe QDs is observed after mixing with TPP, which is speculated to be caused by the energy transfer from QDs of small size to large. This study could be valuable for developing a QD-based drug system for application in two-photon excitation photodynamic therapy.

We describe the trapping characteristic of hyaluronic acid (HA) molecules using silicon micromachined nanotweezers having two opposed needle tips (3-7 µm gap) that were coated with Al, Au, and Pt thin films. In an aqueous HA solution, ac voltage (20 V_pp, sine wave) was applied between the nanotweezer tips. In the experiments using the Al-coated nanotweezers, HA molecules were successfully trapped as a thin string bridged between the tips of the nanotweezers when the frequency of applied ac voltage was 500 Hz or higher. The diameter of the trapped string tended to decrease when the frequency of the applied ac voltage was increased. A molecular string with a diameter of 30 nm consisting of a bundle of multiple HA molecules was obtained when the frequency of the applied ac voltage was 3 kHz. In addition to the Al-coated nanotweezers, HA molecules were also successfully trapped as a string using the nanotweezers with tips coated with Au and Pt thin films.

A tunable reflecting micro-optoelectromechanical systems (MOEMS) micromirror is designed for measuring the actual temperature and color of an object based on comparison of two wavelength response windows, 3-5 and 8-12 µm. The MOEMS micromirror with switching between two positions by an applied electrostatic voltage provides a response to two wavelength windows by tuning the optical resonant cavity. Three different structural models of the tunable micromirror, which are made up of single Al layer with type I legs, single Al layer with type L legs, and double Al/Si₃N₄ layers with type I legs, are designed and simulated accurately using ANSYS tools on a 35-µm pixel-pitch array. On the basis of the comparsion, the third model, made up of double Al/Si₃N₄ layers with type I legs, is chosen. With different distances between the MOEMS micromirror and the bottom electrode, the total capacitance of the tunable micromirror is gained based on electromagnetic analysis and theoretical equation. The pull-in voltage is calculated as 8.21 V by electrostatic-mechanical coupling analysis, and the maximum stress is 368.744 MPa, which is less than the yield strength of Si3N4 thin film. But if the voltage is increased to ~9.73 V, the micromirror will touch the bottom electrode by pull-in behavior.

The polymerase chain reaction (PCR) chips of different metal film thicknesses were fabricated, and the PCR machine with/without a top heater and the single-side/double-side heater PCR chips were compared. Before fabricating the chips, one simulated the effect of various thin-film thicknesses and the temperature distributions of various powers, and it helped one to find the optimum parameters. The total substrate material was cyclic olefin copolymers, and the gold film was fabricated on the substrate by evaporation. The results after PCR for the deoxyri bonucleic acid (DNA) of an Escherichia coli TG-1 cell were obtained. The results of the DNA amplifying 225 bps were 0.84-0.92 ng/µl, and these were 78-85% of the result of PCR machine with a top heater. There was no PCR product in the PCR machine without a top heater and single-side PCR chip. The thermal deformation temperature, thermal conductivity, and substrate thickness are the important parameters in a polymer substrate PCR chip, and the thermal deformation temperature is the key parameter.

We have designed, fabricated, and tested a novel three-dimensional (3-D) flexible microprobe used for recording the neural signals of lateral giant (LG) on the escape system of American crayfish. We report an electrostatic actuation process to fold the planar probes to be the arbitrary orientations of 3-D probes for neuroscience application. The batch assembly method based on electrostatic force techniques gave more simple fabrication compared to others. A flexible probe could reduce both the chronic inflammation response and material fracture when animal breathes or moves. Furthermore, the cortex corresponds to hypothetical cortical modules with mostly vertically organized layers of neurons. Therefore, the 3-D flexible probe suits to understand how the cooperative activity for different layers of neurons. Advisedly, we present a novel fabrication for the 3-D flexible probe by using Parylene technology. The mechanical strength of the neural probe is strong enough to penetrate into a biogel. At the end, the flexible probe was used to record neural signals of the LG cell from American crayfish.

The fundamental study of particle-particle interactions along their line of center in a viscous liquid is valuable on the measurement of atomic force microscopy in liquid phase and the surface force apparatus, and the determination of bulk properties of the suspension in solutions and granular fluid. An equivalent elastohydrodynamic lubrication (EHL) model is proposed for the fundamental study. The surface roughness on the particle surface is modeled as a sphere covered by a porous layer. The collisions between particles are modeled as pure squeeze EHL motion of circular contacts at impact loading. The Stokes equation and the Darcy law are used to describe the flow in the clear fluid region and porous region, respectively. The derived transient modified Reynolds equation, the elasticity deformation equation, ball motion equation, and lubricant rheology equations are solved simultaneously to obtain the transient pressure profiles, film shapes, normal squeeze velocities, and accelerations. The effects of the porous layer thickness and the proportionality constant on the variations of pressure, film thickness, squeeze velocity, squeeze acceleration, relative impact force, total impact time, and the phase shift of the time are discussed.

A UV sensor composed of a surface acoustic wave (SAW) device and a high-frequency amplifier was constructed using a Colpitts oscillator circuit. Zinc oxide (ZnO) films of SAW devices were prepared on lithium niobate substrates with various deposition temperatures to investigate their effect on the sensitivity of UV sensors. Larger grain sizes and a better chemical composition of the ZnO films were obtained at high-deposition temperatures rather than at low-deposition temperatures. An extreme frequency shift of 264 kHz and sensitivity of 0.21 kHz/(µW/cm2) were obtained for the ZnO-based SAW oscillator at the deposition temperature of 400 °C.

An electronic nose (E-Nose) has been studied as a means to realize artificial olfaction. Electronic nose "instruments" are currently relatively large, since the signal manipulation and classification are still done by a personal computer (PC) or a laptop. For this reason, we have developed a portable electronic nose system based on a handheld machine by using a vapor detection array made of carbon-black polymer composites and a sensor circuit. In an effort to make a portable electronic nose, we used thin-film chemical sensors based on the carbon-black polymer nanocomposite to reliably detect chemical warfare agents. To replace the large volume of PCs, we used a field-programmable gate array to perform system control, signal manipulation, and classification. This E-Nose system was exposed to dimethyl-methyl phosphonate (DMMP) and dichloromethane (DCM) in parts per million concentration levels. DMMP and DCM were considered as simulants of the nerve agent sarin and the incapacitating agent BZ gases, respectively.

We present an improved method for manufacturing microfluidic structures on a polymer-based substrate, and the design of experiment (DOE) is used to extract the optimum injection parameters. The long cycle time of the injection molding causes high costs in manufacturing, and this prevents conventional techniques from being widely used for mass production. Therefore, this study adopts a new optical disk process to reduce the cycle time. The cycle time of the new method can be reduced by more than ten-fold compared with that of traditional ones. Also, this new method can prevent damage on the mirror plate of the mold. The mold system is composed of a mold insert (stamper) holder and a vacuum system to join the mold insert with the mold. In this way, the time needed to change the stamper is drastically decreased. Our proposed method has the ability to reduce the time required to insert the mold from several hours to a few minutes, to prevent damage on the mirror plate of the mold, and to decrease the cycle time of molding from several minutes to 4 sec. The DOE is applied to study the effects of molding parameters on replication rate of depth, width deviation, birefringence, tilt and surface roughness of the microfluidic substrates. The experimental results show that the proposed method is suitable for mass production.

The objective of this work is to determine a guideline for defining practical overlay metrology requirements for a given design rule. Total measurement uncertainty (TMU) of overlay metrology is defined as the square root of square sum of the following items: the mean of the tool-induced shift (TIS), TIS 3-sigma, dynamic precision, and tool-to-tool matching. The TMU is dependent upon process conditions, so TMU is different by process layer. In this study, the impact of TMU on overlay error correction, which includes process and measurement noise, is investigated in terms of the stability of high-order overlay correction parameters. By evaluating the variation range of correctable parameters as a figure of merit, the corresponding TMU is determined for a given design rule. Utilizing this methodology, we determined that 2 nm of TMU value is the allowable limit for 45 nm of dynamic random access memory (DRAM) half pitch based upon simulation results. Similarly, we recommend 1 nm of TMU for 36 nm of DRAM half pitch. Our methodology is described and our simulation results are discussed.

Computation lithography relies on algorithms. However, these algorithms exhibit variability that can be as much as 5% (one standard deviation) of the critical dimension for the 65-nm technology. Using hotspot analysis and fixing as an example, we argue that such variability can be addressed on the algorithm level via controlling and eliminating its root causes, and on the application level by setting specifications that are commensurate with both the limitations of the algorithms and the goals of the application.

Step-and-flash imprint lithography (S-FIL^®) is a promising lithography strategy for semiconductor manufacturing at device nodes below 32 nm. The S-FIL 1:1 pattern transfer technology utilizes a field-by-field ink jet dispense of a low-viscosity liquid resist to fill the relief pattern of the device layer etched into the glass mask. Compared to other sub-40-nm critical dimension (CD) lithography methods, the resulting high resolution, high throughput through clustering, 3-D patterning capability, low process complexity, and low cost of ownership of S-FIL makes it a widely accepted technology for patterned media as well as a promising mainstream option for future CMOS applications. Preservation of mask cleanliness is essential to avoid the risk of repeated printing of defects. The development of mask cleaning processes capable of removing particles adhered to the mask surface without damaging the mask is critical to meet high-volume manufacturing requirements. We present various methods of residual (cross-linked) resist removal and final imprint mask cleaning. Conventional and nonconventional (acid-free) methods of particle removal are compared and the effect of mask cleaning on pattern damage and CD integrity is also studied.

The finite-difference time-domain (FDTD) method is used as rigorous electromagnetic analysis model to calculate the field for a diffractive microlens (DML). The FDTD is used for the entire solution rather than using a near- to far-field propagation method to obtain the far-field energy distribution; thus, all the results are vector based. We derived a formula to calculate the magnitude of electric field, which is time dependent and can be used to graphically show the light wave propagation and focusing process through a DML. Both the comparison and the integral methods are presented to obtain wave amplitude in full solution space, and the distribution of light energy behind a DML is illustrated based on the wave amplitude. The formula of diffractive efficiency of the DML is derived from a time-averaged Ponyting vector, which can indicate the propagation direction of light energy. Application of these formulations in the analysis of a DML example demonstrates the high accuracy and efficiency of our method.

Focused ion beam (FIB) was employed to fabricate nanoimprint lithography stamps. Complex micro/nanopatterns were fabricated in the stamp, including curved nanograting structures. These micro/nanostructures were then replicated to SU-8 2000.1 resist, with an imprint temperature of 95 °C, which is lower than for conventional imprint polymers. Atomic force microscopy was used to characterize the surface profiles of stamp and replica's and the replication fidelity as well. The results show that nanoimprint with the FIB fabricated stamp can successfully replicate complex micro/nanostructures under low temperature in SU-8.

Plant-based resist materials with liquid trehalose derivatives are investigated to achieve low volumetric shrinkage in ultraviolet curing nanoimprint lithography. This procedure is proven to be suitable for resist material design in the process conditions of ultraviolet curing nanoimprint lithography. The developed plant-based resist material using liquid trehalose derivatives with epoxy groups produces high-quality imprint images of 65-nm line and space. The distinctive bulky glucose structure in trehalose derivatives is considered to be effective for minimizing volumetric shrinkage of resist film during ultraviolet polymerization.

A novel fabrication method for corrugated long-period fiber gratings (CLPFG) is presented in this study. The patterned SU-8 photoresist is used as a double-side stopper layer for a wet-etching process to fabricate the CLPFG. Presented in this research are four types of CLPFG with periods of 660, 670, 680, and 690 µm and resonant wavelengths of 1531, 1539, 1550, and 1558 nm, respectively. The maximum resonance loss of the CLPFG with a 680-µm period is 23 dB. The CLPFG fabricated in this study is demonstrated for temperature sensing, and the results illustrate that the fabricated CLPFG with a 680-µm period has a temperature sensitivity of 58.4 pm/°C, a wavelength-shifting linearity of R²=0.994, and a 0.856 °C resolution.

A complementary metal-oxide semiconductor (CMOS)-compatible, capacitive, shunt-type radio frequency MEMS switch design is demonstrated. The switch is actuated by an electrothermal actuator and an electrostatic actuator at the same time, and the switching status is latched by electrostatic force only. Since thermal actuators require a lower voltage than electrostatic actuators, and since an electrostatic force can maintain switching status with virtually no power, the benefits of the mechanism are a very low actuation voltage and low power consumption. The switch is fabricated by a standard 0.35-µm 2P4M CMOS process. The movable membrane can be released by either wet or dry postprocessing etching technologies. The design's CMOS-process compatibility is important because radio frequency (RF) characteristics are determined not just by the device itself. The design can minimize parasitic capacitance when a packaged RF switch and a packaged IC are wired together. The switch contains a set of coplanar waveguide transmission lines and a suspended membrane. The CPW lines and the membrane are contained in the metal layers of the CMOS process. The electrothermal actuators are contained in the polysilicon layer. Only standard CMOS process layers are needed for both the electrothermal and electrostatic actuations in the RF switch. The measurement results show that the electrothermal or electrostatic actuation requires less than 7 V.

Nongyro inertial measurement units (NGIMUs) use only microelectromechanical system or microaccelerometers replacing gyroscopes to compute the motion of a moving body. The angular information of NGIMU can be acquired from linear acceleration information. In this work, a new nine-accelerometer configuration of NGIMU is presented with a built experiment system. To improve the precision of the estimated angular rate, a compensation algorithm is used to get the correct accelerometer output. It is provided under the existence of the accelerometer mounting error, which seriously affects NGIMU performance. The simulation study of the proposed methods for estimating the angular rate is investigated based on the present NGIMU configuration. Additionally, the experiment verification using the two-axis turntable to measure the angular rate is also performed. The simulation and experiment results show the feasibility of the configuration and methods. In the experiment, the relative error of this nine-accelerometer configuration is around 1% when the measured angular rate ranges from 0 to 200 deg/s.

Numerical calculations are performed to investigate the effect of the component of a single transducer pulse on the ejection of a drop for a drop-on-demand ink-jet printhead with a piezoelectric actuator. The flow field is governed by continuity and Navier-Stokes equations. A volume-of-fluid method with a piecewise-linear interface construction is used to track the complicated topological variation of the liquid-gas interface. The computer code is validated with experimental results present in the literature. The volume of the primary drop is closely related to the maximum displacement D_f of chamber wall induced by the piezoelectric actuator in the forward stoke; the velocity of the primary drop depends on the ratio of D_f to the time period of the forward stoke Δτf. Moreover, the fact that the formation of the primary drop depends weakly on the conditions of the backward stroke is considered. A decreased interval between forward and backward strokes might serve to suppress the formation of satellite drops owing to reducing the liquid thread length ∫_b at pinching off to a value less than the upper limit ∫^*_b. The breaking up of the freely flying liquid thread from nozzle outlet has two modes-multiple breaking up and end pinching-and depends on the thread length at pinching off.

Nanopore-based single-molecule analysis is a subject of strong scientific and technological interest. Recently, solid state nanopores have been demonstrated to possess advantages over biological (e.g., protein) pores due to the relative ease of tuning the pore dimensions, pore geometry, and surface chemistry. Previously demonstrated methods have been confined to the production of single nanopore devices for fundamental studies. Most of these techniques (e.g., electron microscope beams and focused ion beams) are limited in scalability, automation, and reproducibility. We demostrate a wafer-scale method for reproducibly fabricating large arrays of solid state nanopores. The method couples high-resolution electron-beam lithography and atomic layer deposition (ALD). Arrays of nanopores (825 per wafer) are successfully fabricated across 4-in. wafers with tunable pore sizes. The nanopores are fabricated in 16- to 50-nm thin silicon nitride. ALD of aluminum oxide is used to tune the nanopore size. By careful optimization of the processing steps, a device survival rate of up to 96% is achieved on a wafer with 50-nm thin silicon nitride films. Our results facilitate an important step in the development of large-scale nanopore arrays for practical applications such as biosensing.

The light-emitting diode (LED) has been extensively applied to lighting systems. In this work, a novel optical structure design of a microlens based on reflection/refraction properties can achieve a specific light-focusing effect, and can be applied to LED packaging. The optical microlens structure from basic specifications of conventional LED packaging are modified and redesigned. The light-focusing performance of this novel focused microlens is greatly enhanced, and the energy of the LED light within a range ±15 deg from the center line of the light source can be greatly improved as well. Maximum illuminance is enhanced 99.3% in comparison with conventional LED packaging, and the luminous flux rayed out within a range ±15 deg from the center line of the light source is enhanced 34%. The achievements of this research can be applied to various kinds of working environments to meet specific focusing requirements with energy savings.