Setting Up High-Throughput Low-Volume Sequencing and PCR Reactions Using an Automated System Equipped with Precision Glass Syringes and a Non-Contact Microsolenoid Dispenser

The advantages of using a new automated system, the Hydra-Plus-One System equipped with 96 or 384 precision glass syringes and a non-contact microsolenoid dispenser, in setting up high-throughput low-volume sequencing reactions and PCR are described. Using the syringe-based dispenser, which is the Hydra-PP part of this system, wet dispenses of as small as 100 nL with CVs of less than 10% can be accomplished. The single-channel, non-contact microsolenoid dispenser part of the system can dispense samples as low as 100 nL (with CVs of less than 10%) at a speed of 58s per 96 dispenses into any plate format (SBS footprint). The advantages associated with the use of the Hydra-Plus-One System for setting up PCR and sequencing reactions are high precision at nanoliter-dispense range; speed; and minimal waste of precious and expensive samples. The single-channel dispenser eliminates the dead volume associated with aspirating from reservoirs or troughs and thereby reduces sample waste. In addition, virtually all material can be recovered from the dispenser. Finally, non-contact dispensing enables distribution of sample into wells without any inbetween-dispenses washing requirements.     

Interfacing microfluidics to LDI-MS by automatic robotic spotting

We developed a method of interfacing microfluidics with mass spectrometry (MS) using a robotic spotting system to automate the contact spotting process. We demonstrate that direct and automated spotting of analyte from multichannel microfluidic chips to a custom microstructured MALDI target plate was a simple, robust, and high-throughput method for interfacing parallel microchannels using matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). Using thermoplastic cyclic olefin copolymer (COC) polymer microfluidic chips containing eight parallel 100 μm × 46 μm microchannels connected to a single input port, spotting volume repeatability and MALDI-MS signal uniformity are evaluated for a panel of sample peptides. The COC microfluidic chips were fabricated by hot embossing and solvent bonding techniques followed by chip dicing to create open ends for MS interfacing. Using the automatic robotic spotting approach, microfluidic chip-based reversed-phase liquid chromatography (RPLC) separations were interfaced with electrochemically etched nanofilament silicon (nSi) target substrate, demonstrating the potential of this approach toward chip-based microfluidic separation coupled with matrix-free laser desorption/ionization mass spectrometry.     

Structure quality in deep X-ray lithography applying commercial polyimide-based masks

The structure quality of deep X-ray lithography components strongly depends on the quality of the applied X-ray mask. In this article we compare the results obtained with two different mask types. Sophisticated working masks generated by e-beam lithography, soft X-ray lithography and electroplating of gold absorbers on a titanium mask membrane have been fabricated at the Institute for Microstructure Technology, Research Center, Karlsruhe (FZK/IMT), Germany. Prototype masks generated by e-beam lithography, optical lithography and electroplating of gold absorbers on a polyimide mask membrane have been fabricated by Optnics Precision, Japan, with the aim to offer commercially available low cost masks. Both mask types were applied to pattern PMMA resist layers of 300–750 μm thickness at the 2.5 GeV electron storage ring ANKA, Germany, using comparable process parameters. FZK/IMT masks provide microstructures with significantly better structure quality. The layout area, however, is currently limited to 12 cm², and the Ti mask membrane tends to lead to a slight resist surface attack, such as rounding of the resist edges. Optnics masks provide microstructures with reduced structure quality due to sidewall striations (sidewall roughness up to 2 μm) and thermal distortions (of up to 3–5 μm) which limit the potential scope of applications. They could nevertheless potentially be applied as low quality, low cost X-ray masks. High resolution and high accuracy applications, however, require more sophisticated but also more expensive masks, like the Ti-masks from FZK/IMT.     

A Microcantilever-Based Picoliter Droplet Dispenser With Integrated Force Sensors and Electroassisted Deposition Means

This paper introduces a picoliter droplet dispenser relying on an array of silicon microcantilevers. The microcantilevers bear fluidic channels, and liquid transfer is achieved by a direct contact of the cantilever tip and the surface. A high degree of control over the location and geometry of the fabricated patterns is ensured by incorporating force sensors and electroassisted deposition means, i.e., electrowetting actuation and electrospotting, to the devices. The cantilever array, a PC-controlled stage, and an electronic circuit dedicated to the piezoresistance measurements form a closed-loop system that enables the automatic displacement of the array and the control of the deposition parameters. By using an external loading chip, different liquids are loaded onto the cantilevers, enabling the parallel deposition of several entities in a single spotting run. This paper details the design of the cantilevers assisted by finite-element modeling, the fabrication of the cantilever array, and the closed-loop operation. Moreover, proof-of-concept experiments are presented to demonstrate the versatility of our deposition system in terms of deposited materials and spot sizes. The control of the spotting process, the versatility of the printed materials, and the added electroassisted features prove that this tool has a real potential for research work and industrial applications.     

Polyimide micro-channel arrays for peripheral nerve regenerative implants

Mechanical guidance is one way in which regenerating axons can be directed towards an appropriate target. In this paper, we present the design and fabrication process of a three-dimensional (3D) device comprising a bundle of parallel micro-channels, which can be used as a 3D regenerative implant for peripheral nerve repair. The skeleton of the device is entirely made of flexible polyimide films. Gold micro-electrodes and micro-channels of photosensitive polyimide are patterned directly on polyimide substrates. After fabrication, the 2D electrode channel array is rolled into a 3D channel bundle fitting the peripheral nerve.The efficiency with which axons enter the 2D channel array was evaluated in vitro as a function of channel width, spacing and pitch. Axon outgrowth is maximised when micro-channels are wide (>30 μm), and when the array transparency (the channel width to pitch ratio) is at least 50%. To ensure the metallic electrodes remain functional in the rolled device, substrate thickness and micro-channel height must also be optimized to position the metal film in the neutral plane of the rolled structure. Electrodes embedded in the implant polyimide structure are robust to rolling. Their impedance at 1 kHz in Ringer solution is of the order of 1 MΩ on flat samples, and changes little when the same samples are rolled and inserted into 1.5 mm inner diameter tube. Such 3D, electrode channel devices on polymer not only provides a novel technological approach to physical guidance of regenerating neurons in vivo but also enables the fabrication of an electrode implant with direct electrical communication with multiple groups of nerve fibres in a regenerating peripheral nerve.     

Selection of high strength encapsulant for MEMS devices undergoing high-pressure packaging

Deflection behavior of several encapsulant materials under uniform pressure was studied to determine the best outer encapsulant for MEMS device. Encapsulation is needed to protect movable parts of MEMS devices during high-pressure transfer molded packaging process. The selected outer encapsulant material has to have surface deflection of less than 5 μm under 100 atm vertical loading. Deflection was simulated using Coventorware ver.2005 software and verified with calculation results obtained using shell bending theory. Screening design was used to construct a systematic approach for selecting the best encapsulant material and thickness under uniform pressure up to 100 atm. Materials considered for this study were SMC polyimide, liquid crystal polymer (LCP) carbon fiber and polyphenylene sulfide (PPS) high modulus carbon fiber. It was observed that PPS high modulus carbon fiber has deflection of less than 5 μm for all thickness and pressure variations. LCP carbon fiber is acceptable and SMC polyimide is unsuitable as high strength encapsulant. PPS high modulus carbon fiber is considered the best encapsulation material for MEMS under high-pressure packaging process due to its high strength. The generalized mathematical model and equations developed for predicting deflection of encapsulation under uniform loading could be used to determine the suitability of any candidate material and encapsulation design with similar domed shaped structure.     

Cognitive load in hypermedia reading comprehension: Influence of text type and linearity

In this paper the assumption of cognitive overhead in hypermedia learning is specified by cognitive load theory. This analysis is based on different types of cognitive load, the dimension of linearity/non-linearity as well as text characteristics. We propose a model stating that extraneous cognitive load in hypermedia learning is basically determined by the interaction of text presentation format (linear/non-linear) with text type (text with and without narrative structures). This assumption was tested by means of a 2 × 2 experimental design. Sixty participants completed a computer-based learning program that contained a narrative text or an encyclopaedia text in either linear or non-linear presentation format. Results confirm the suggested interaction hypothesis postulating that non-linear information presentation of narrative text structure increases cognitive load and decreases knowledge acquisition. However, for encyclopaedia text participants’ knowledge acquisition was not affected by linear or non-linear presentation format. Furthermore, results suggest a cross-validation of cognitive load measures and propositional analysis.     

Surface micromachined polyimide scanning thermocouple probes

This paper describes micromachined scanning thermocouple probes that exploit the low thermal conductivity and the high mechanical flexibility of polyimide as a structural material. They are surface micromachined using a low-temperature six-mask process suitable for appending to a CMOS fabrication sequence. The probes are 200-1000-μm long, 40-120-μm wide, and of varying thickness. They are assembled by a flip-over approach that eliminates the need for dissolving the substrate wafer or removing the probe from it. Temperature sensing is provided by thin-film Ni/W or chromel/alumel thermopiles embedded in the polyimide, which provide Seebeck coefficients of 22.5 and 37.5 μV/K per junction, respectively. Modeling results indicate that the low thermal conductivity of polyimide causes the temperature drop along the probe length to be much higher than with other candidate materials such as Si or SiO₂, which contributes to improved thermal isolation of the sample and higher temperature sensitivity of the probe. However, the response time of the probe is compromised, and the measured -3 dB bandwidth of the probes is ≈500 Hz. A sample scan is presented     

Power saving through state retention in IGZO‐TFT AMOLED displays for wearable applications

We present a qHD (960 × 540 with three sub‐pixels) top‐emitting active‐matrix organic light‐emitting diode display with a 340‐ppi resolution using a self‐aligned IGZO thin‐film transistor backplane on polyimide foil with a humidity barrier. The back plane process flow is based on a seven‐layer photolithography process with a CD = 4 μm. We implement a 2T1C pixel engine and use a commercial source driver IC made for low‐temperature polycrystalline silicon. By using an IGZO thin‐film transistor and leveraging the extremely low off current, we can switch off the power to the source and gate driver while maintaining the image unchanged for several minutes. We demonstrate that, depending on the image content, low‐refresh operation yields reduction in power consumption of up to 50% compared with normal (continuous) operation. We show that with the further increase in resolution, the power saving through state retention will be even more significant.     

Average power handling capability of multilayer microstrip lines

This article describes the average power handling capability (APHC) of multilayer microstrip lines, including the effect of mismatch at the terminations. The data presented herein are validated by considering an example of a 12‐W monolithic microwave integrated circuit power amplifier fabricated using multilayer low‐loss microstrip technology. The calculated value of APHC for a 50‐Ω line of a 75‐μm‐thick GaAs substrate is 1445 W at 10 GHz, whereas the corresponding value for a multilayer microstrip that has 10‐μm‐thick polyimide is only 44 W. At 40 GHz, these values are reduced by a factor of 2. © 2001 John Wiley & Sons, Inc. Int J RF and Microwave CAE 11: 385–395, 2001.