In this paper, we will discuss our recent approaches for improving the mechanical stability of free-standing bilayer lipid membranes (BLMs) by combining with BLM formation and microfabrication techniques. BLMs were prepared across a microaperture fabricated in a silicon (Si) chip and their mechanical stability and electric properties were investigated. BLMs suspended in a thin Si3N4 septum showed a dramatic improvement of BLM stability. The BLMs were resistant to voltage of ±1 V and the membrane lifetime was 15- ~40 h with and without incorporated channels. The membrane containing gramicidin channel exhibited tolerance to repetitive solution exchanges. At first, electric properties of the BLMs, such as noise level and current transient, were necessary to be improved. However, after coating the chip with insulator layers of Teflon and SiO2, total chip capacitance was reduced, leading to noise reduction (1-2 pA in peak-to-peak after low-pass filtering at 1 kHz) and elimination of current transients (< 0.5 ms). Since the vicinity of the aperture edge was remained uncoated, the BLMs formed in the Si chips still showed high mechanical stability after the insulator coatings. The mechanically stable BLMs having electric properties suitable for recording activities of biological channels will open up a variety of applications including high-throughput analysis of ion-channel proteins.

Capacitive CMOS MEMS sensors are usually defined by anisotropic dry etching processes (RIE and DRIE). These processes can provide clean and vertical sidewall geometry. However, during the dry-etching processes, charges are added to the gate electrodes of the on-chip MOSFET’s through metal pads and micro-structures, and the voltage may be raised to the level of breaking down the gate oxide, which leads to large leakage current and fails the circuit. On another hand, the thin spring beams in capacitive CMOS MEMS accelerometers suffer from in-plane curling and out-of-plane curling caused by stress gradient. Furthermore, the stress in the layers of MEMS structure is a function of temperature. Therefore, the in-plane curling and out-of-plane curling vary with temperature, leading to varying electrode coupling area in the sensing beams. This in turn causes variation in the sensitivity and the DC offset of sensors, meaning that usually the thermal stability of CMOS MEMS capacitive accelerometers is very poor. To cope with these problems, this work develops a new wafer-level post-CMOS process for fabricating thermally stable capacitive accelerometers. The resultant MEMS structures have high aspect ratio (e.g. 2-2.5 μm gaps versus 57 μm depth) and are insensitive to residual stress as well as temperature change. Excellent thermal stability was achieved intrinsically by making the crystalline Si layer in the sensors thick. Moreover, this process totally avoids the charge damage problem during the dry-etching procedure. For demonstration, an accelerometer sensor was fabricated by using the proposed process and was integrated with an on-chip sensing circuit in commercial 0.35 μm 2P4M CMOS process. High detection sensitivity of 595 mV/g and very low thermal variation of 1.68 mg/°C were successfully achieved.

Abrasive blade dicing is the most common technique for die separation. In this work an alternative dry and non-abrasive die separation method, which is known as "Stealth dicing", is assessed for surface-sensitive MEMS (Micro Electro Mechanical Systems) wafers. The dicing performance and capability of the system is investigated on 200mm full thickness wafers with and without MEMS structures. The diced wafers are analyzed with respect to the silicon cutting quality, possible particle contamination, the condition of functional structures and their mechanical and electrical functionality. In addition the performance and limitations of two different Stealth Dicing Engine (SDE) types, SDE01 and SDE03, are compared to each other with respect to their performance on MEMS wafer dicing.

From this work design rules and proper dimensions of the scribe line can be determined. Process integration solutions, describing steps before and after the Stealth dicing process, including the contact-less dicing tape application to the wafer back side and the final die separation method by tape stretching, are presented. It was also found that the SDE03 laser with its outstanding performance in terms of process speed and separation quality can bring a breakthrough for applying this technology for MEMS wafers.

The electrochemiluminescence (ECL) and surface plasmon resonance (SPR) based immunosensors for measuring a trace level of disease markers are shown. It is well known that thiols form a self-assembled monolayer on a metal surface, and this has been widely used to modify metal surfaces. We employed this characteristic for a highly sensitive immunosensors by obtaining a surface pre-concentration of thiol molecules formed by the enzymatic reaction of labeled antibody.

With the aid of negative dielectrophoresis (nDEP) force in conjunction with shear force and at an optimal sodium hydroxide (NaOH) concentration we demonstrated a switch-like functionality to elute immuno-bound beads from the surface. At an optimal flow rate and NaOH concentration, nDEP turned on results in bead detachment, whereas when nDEP is off, the beads remain attached. This platform offers the potential for performing a bead-based multiplexed immunoassay where in a single channel various regions are immobilized with a different antibody, each targeting a different antigen. As a proof of concept we demonstrated the ability of nDEP to provide this switching behavior in a singleplex assay for the interactions that were in the same order of magnitude in strength as typical antibody-antigen interactions.

Gallium nitride (GaN) is a robust piezoelectric semiconductor with excellent thermal and chemical stability, making it an attractive material for surface acoustic wave (SAW) sensors operating in high temperature and harsh environments. The sensitivity of SAW devices is proportional to the square of the operating frequency. Therefore, high operating frequencies into the GHz regime are desirable for SAW sensors. For GaN, this requires sub-micron interdigital transducers (IDTs) when devices are designed to operate at the fundamental Rayleigh mode frequency. The necessity for sub-micron IDTs can increase fabrication costs and complexity. By designing SAW devices to operate at harmonic frequencies, GHz operation can be realized with relatively large IDTs, resulting in simpler and more cost effective solutions for GaN based SAW sensors. Devices have previously been designed to operate at the 5th and higher harmonics on lithium niobate, but there are no reports of using this technique on GaN in the literature. In this study, GaN thin films have been grown via metal organic vapor phase epitaxy on sapphire substrates. SAW devices designed to operate at the fundamental frequency and higher harmonics have been fabricated and measured. Operating frequencies greater than 2 GHz have been achieved using IDTs with 5 μm fingers. In addition, reduction of electromagnetic feedthrough around the 5th and 7th harmonic is demonstrated through varying ground electrode geometries.

Engineering and manufacturing of thick and bio-functional tissue products is one of the big issues in tissue engineering. To produce such tissues, we need some innovative technologies, which enable us to build up thick, three-dimensional structures and to arrange multiple types of cells to make complicated tissue structures. Based on such considerations, we have developed a custom-made inkjet 3D bioprinter, which realized both of direct cell printing and 3D laminating printing with cells and hydrogel. Recently, it has been improved, and here we report recent progresses and our achievements with new version 3D bioprinter.

Image based printing mode and active Z-axis control system were added. As a useful structure, an image of multi-honeycomb pattern was designed in computer and next it was copied and finally in total 100 image data were prepared. Using those digital data, 3D image of thick multi-honeycomb structure was reconstructed in computer, and then, laminating printing was carried out using our new version 3D bioprinter with alginate hydrogel. The new version printer showed good performance of 3D laminating printing and finally complicated 3D multi-honeycomb hydrogel structures could be successfully fabricated. It is indicated that fabrication of cell containing 3D structures based on the computer aided designs is feasible and that such biofabrication technologies must contribute to further innovative advancement of tissue engineering.

We have investigated the criterion of interfacial crack initiation in nanometer-scale components (nano-components) by means of a loading facility built in a transmission electron microscope (TEM). Three types of experiments are conducted in this project. (1) In order to clarify the applicability of conventional continuum mechanics to the nano-components, we prepare cantilever specimens with different size, which introduce different stress fields, containing an interface between a 20 nm-thick copper (Cu) thin film and a silicon (Si) substrate. These demonstrate the validity of the “stress” criterion even for the nano-scale fracture. (2) In order to examine the effect of microscopic structure on the mechanical property, we fabricate a bending specimen in the nano-scale with thin Cu bi-crystal (the thickness of about 100 nm) formed on Si substrate, of which understructure can be observed in situ by means of a TEM during the mechanical experiment. The initial plastic deformation takes place near the interface edge in a grain with a high critical resolved shear stress and expands preferentially in the grain. Then, the plasticity appears near the between Cu grain boundary and Cu/Si interface, and this development brings about the interfacial cracking from the junction. These indicate the governing influence of understructure on the mechanical property in the nano-components. (3) In order to investigate the fatigue behavior of metal in a nano-component, a cyclic bending experiment is carried out using nano-cantilever specimens with a 20 nm-thick Cu constrained by highly rigid materials (Si and SiN). The high strain region is in the size of 20-40 nm near the interface edge. The specimen breaks along the Cu/Si interface before the maximum load under the fatigue loading. The load-displacement curve shows nonlinear behavior and a distinct hysteresis loop, indicating plasticity in the Cu film. Reverse yielding appearing after the 2nd cycle suggests the development of a cyclic substructure in the Cu film. These indicate that the crack is caused by characteristic understructure owing to fatigue cycles.

Nanoporous gold (np-Au) is a promising nanostructured material with many desirable properties, including large surface area-to-volume ratio, corrosion resistance, high conductivity, and well-studied thiol-based surface chemistry. While np-Au has been used in a variety of applications, from fuel cells to electrochemical sensors, its interface with biology, where many of its exciting applications lie, is surprisingly non-existent. This paper reports on drug delivery from np-Au thin films for modifying cell proliferation in situ. We expect that establishing np-Au as a biomaterial with drug delivery capabilities will create new opportunities for engineering advanced BioMEMS devices that can monitor and modulate biological processes in both in vitro and in vivo settings.

Convenient preparation of nano/micro scale topography is crucial for the fabrication of low-cost biodevices, which could be useful tools for understanding cell biology mechanisms and for the development of scaffolds for tissue engineering. Such intelligent surfaces have been conventionally fabricated through photolithography, micro-contact printing, and nano/micro imprinting. However, considering the process integration, these approaches are not always adequate in order to produce large dimensional patterns in a convenient and rapid way. In this study, we focused on the convenient fabrication of nano-wrinkles based on the elastic instability between a shape memory polymer sheet and a conductive polymeric film, on which the behavior of murine skeletal muscle cells (C2C12) was evaluated. A tens-of-nm-thick layer of poly(3,4-ethylenedioxythiophene) with poly(styrenesulfonate) (PEDOT:PSS) was spincoated on a thermo-retractable polymer sheet. Then, thermal treatment produced different periodicity of the unidirectional nano-wrinkles on the polymer sheet covered with different thickness of PEDOT:PSS layer. Finally, adhesion and proliferation of C2C12 were evaluated, comparing different samples. The cells preferentially adhered and anisotropically aligned on low and narrow ridges (1.5 μm height) rather than on high and wide ones (2.5 μm height). Furthermore, we observed that these trends were confirmed in the differentiation stage of C2C12 into myotubes. The combination of living cells and tunable nano-wrinkles made of conductive polymeric materials will represent a unique tool for the development of innovative biomedical devices.

This paper describes the implementation of a custom-made bio-microelectromechanical system for determining mechanical properties of biological cells, which is used for the measurement of mechanical properties of fibroblasts. Our system consists of several subcomponents: (a) actuator which deforms the cell in pre-determined, step-wise fashion, (b) force sensor that measures force applied onto the cell, (c) set of dielectrophoretic (DEP) electrodes for positioning cells in the desired position, (d) temperature sensors and (e) heater. Preliminary results of the mechanical properties of NIH3T3 cells have been determined using this tool and our cell compression techniques.

This work presents the successful production, via a simple oxidation process, of Ti-TiOx-Pt Metal-Oxide-Metal diodes with excellent electrical asymmetry. TEM analysis has been used to verify the oxide thickness. A thicker layer produces better diodes, although they are of a less uniform nature. The conduction mechanism in these diodes is still under investigation.

Nanostructured carbons have been widely used for fabricating enzyme-modified electrodes due to their large specific surface area. However, because they are random aggregates of particular or tubular nanocarbons, the post-modification of enzymes to their intra-nanospace is generally hard to control. Here, we describe a free-standing film of carbon nanotube forest (CNTF) that can form a hybrid ensemble with enzymes through liquid-induced shrinkage. This provides in-situ regulation of itsintra-nanospace (inter CNT pitch) to the size of enzymes, and eventually serves as a highly active electrode. The CNTF ensemble with fructose dehydrogenase (FDH) showed the oxidation current density of 16 mA cm-2in stirred 200 mM fructose solution. The power density of a biofuel cell using the FDH-CNTF anode and the Laccase-CNTF cathode reached 1.8 mW cm-2(at 0.45 V) in the stirred oxygenic fructose solution, more than 80 % of which could be maintained after continuous operation for 24 h. Application of the free-standing, flexible character of the enzyme-CNTF ensemble electrodes is demonstrated via their use in the patch or wound form.

Biofilms are a common cause of persistent infections on medical devices as they are easy to form and hard to treat. Selenium and its compounds are considered to be a novel material for a wide range of applications including anticancer applications and antibacterial applications. The objective of this study was to coat selenium nanoparticles on the surface of polycarbonate medical devices and examine their effectiveness at preventing biofilm formation. The results of this in vitro study showed that the selenium coating significantly inhibited Staphylococcus aureus growth on the surface of polycarbonate after 24 hours. Thus, this study suggests that coating polymers with nanostructured selenium is a fast and effective way to reduce bacteria functions leading to medical device infections.

We have developed a microfluidic sensor to measure the electrical coupling through gap junctions across a 2D sheet of cultured Normal Rat Kidney cells. The chip is based on a tri-stream laminar flow with conductive solutions on either end and a nonconductive solution in the middle stream. When an electrical voltage is applied, the current can only pass through the cell sheet, thereby enabling us to measure the electrical coupling of gap junctions between cells. Using this sensor we have measured the effect of 2-aminoethoxydiphenyl borate (2-APB) on Cx43 channels. We show that 2-APB reversibly inhibits electrical coupling of Cx43 in NRK cells. Moreover, we screened other potential candidates to block Cx43, 1-Heptanol and GsMTx-4, and examined their effects on Cx43 gap junctions.

The use of non-standard materials (e.g. specific substrates shapes and dimensions or polymer materials) for MEMS applications imposed a requirement for the development of new techniques for even well-established processes. Acoustic energy in the MHz frequency range has been used in the semiconductor industry for various processes such as photoresist development, substrate cleaning and electro-plating enhancement. The work presented here is focusing on single wafer cleaning and on photoresist development.

The cleaning process developed addresses mainly wafer cleaning prior to wafer bonding processes, in which particle contamination is of crucial importance.

The photoresist development process was developed mainly for thick resist layers development (few hundreds of μm) in order to improve definition of high aspect ratio features but was used as well as a significant process time reduction factor for development of regular thickness resists (few μm).

A unique simulation method of epoxy-based chemically-amplified resist by coarse-grained molecular dynamics was proposed. The mechanical properties of an epoxy-based chemically-amplified resists with various cross-linking ratios were simulated using a newly developed coarse-grained molecular dynamics simulation that employs a bead-spring model. Models with the different cross-linking ratios were created in the molecular dynamics calculation step and uniaxial elongation simulations were performed. The results reveal that the simulated elastic modulus of the resist modeled by the bead-spring model with an extended angle bending potential depends on the cross-linking ratio; its dependency exhibits good agreement with that determined by nanoindentation tests.

We present a rapid and sensitive surface acoustic wave (SAW) immunosensor that utilizes gold staining as a signal enhancement method. A sandwich immunoassay was performed on sensing area of the SAW sensor, which could specifically capture and detect cardiac markers (cardiac troponin I (cTnI), creatine kinase (CK)-MB, and myoglobin). The analytes in human serum were captured on gold nanoparticles (AuNPs) that were conjugated in advance with detection antibodies. Introduction of these complexes to the capture antibody-immobilized sensor surface resulted in a classic AuNP-based sandwich immunoassay format that has been used for signal amplification. In order to achieve further signal enhancement, a gold staining method was performed, which demonstrated that it is possible to obtain gold staining-mediated signal augmentation on a mass-sensitive device. The sensor response due to gold staining varied as a function of cardiac marker concentration.

Next-generation bioanalytical approaches for protein-level measurements are advanced by the integration capacity of microfluidic design strategies, as well as the fine fluid and material control possible. Photopatterning of polymers within fluidic volumes is a key tool in the suite of technologies available for seamless integration of assay measurement modalities, as well as rapid target detection. Here, we overview recent advances in heterogeneous and homogeneous immunoassays using functional polymers, electrophoretic transport, and microdevices.

Our previous studies proved the occurrence of the shape memory effect (SME) in a biocompatible porous nitinol (inter-metallic phase NiTi), obtained by the selective laser sintering (SLS) method. In this report we propose to use the SME peculiar to the nitinol, for a functional design of the drug delivery system and to discuss the process flow pattern. In living tissues (flesh) the elevated temperature at the disease origination leads to the nitinol pores size reduction caused by the austenite phase transformation, and to the pharmaceutical composition extrusion from the pores. And vice versa, during the cooling stage when the tissue temperature reverts to normal level, the drug intake will stop. Depending on the type of the three dimensional structure of a porous matrix (scaffold) identified at the stage of a computer-aid-design, the velocity of penetration can be controllable.