Papers by Keyword: Biochip

Abstract: Prolonged monitoring is more likely to result in an accurate diagnosis of atrial fibrillation patients than intermittent or short-term monitoring. In this study, we present an implantable ECG sensor to monitor atrial fibrillation patients in real time. The developed implantable sensor is composed of a micro controller unit, analog to digital converter, signal transmitter, antenna, and two electrodes. The sensor detects ECG signals from the two electrodes and transmits these signals to the external receiver that is carried by the patient. The sensor continuously transmits signals, so its battery consumption rate is extremely high. To overcome this problem, we consider using a wireless power transmission module in the sensor module. This module helps the sensor charge power wirelessly without holding the battery in the body. The size of the integrated sensor is approximately 0.12 inch x 1.18 inch x 0.19 inch. This sensor size is appropriate enough for cardiologists to insert the sensor into patients without the need for a major surgery. The data sampling rate was 300 samples/sec, and the frequency was 430 Hz for signal and power transmission. To verify the validation of the developed sensor, the small animal experiments were conducted.

Abstract: We present a new design of biochip for application in clinical diagnostics by using a conventional method of pattern transfer process in microelectronic fabrication. Although there are many advanced techniques available to produce nanostructures such as electron beam lithography (EBL), ion-beam lithography (IBL), focused ion beam milling and nanoimprint lithography, these methods often requires high maintenance costs, time consuming and very complicated compared to conventional photolithography. This conventional technique is still a good choice for a feature size more than 1 micron. In this work, microbridge and microgap design from chrome mask are transferred on silicon wafer to fabricate a biochip. The pattern transfer of the first mask of electrode is presented in this paper to test the repeatability of pattern transfer during photolithography process. Therefore, during the process, the resolution and precise alignment factors are taken into account to prevent circuit and device failure. Post-exposure bake time and development limitations are recorded for both designs.

Abstract: In Micro/Nanowire fabrication, the alignment and exposure process are the most critical steps in photolithography process, and indeed for the whole biochip processing. This process determines the success of transferring the Micro/Nanowire design pattern on the mask to the photoresists on the wafer surface. Hence, the resolution requirementsand precise alignment are vital; each mask needs to be precisely aligned with original alignment mark in order to transfer the original pattern from mask onto photoresist layer. Otherwise, itcant successfully transfer the original pattern to the wafer surface causing device and circuit failure. Therefore, the UniMAPs Second Generation Mask Aligner is used for precise alignment and pattern transfer process. Thus, the paper present a preliminary study on fundamentals of resist exposure and development mechanisms for fabrication of Micro/Nanowire, We demonstrated significance of considering process parameters such as mask aligner, quality of resist, soft bake, exposure time and intensity, and development time. There was a very little room for alignment error; we were able to achieved error free design to the criticaldimension.

Abstract: A kind of gene detection biochip model based on biological micro electro mechanical systems (BioMEMS) technology and micro optical electro mechanical systems (MOEMS) technology is designed and simulated. In order to detect whether there are nucleic acid components in the testing samples, the biochip in this study issues horizontal light by laser, then receives and reads the deformation signals of MEMS cantilever by optical detector. The MEMS optical reflecting system can amplify MEMS cantilever deformation signal 22 times by micro reflectors which are set on the side wall of the cantilever free end. In order to improve optical detection sensitivity, gold nanoparticles (GNPs) which are combined with hybridization information is taken to aggravate MEMS cantilever, and employ Au - S chemical bond of GNPs and dithiol HS(CH₂)₆SH to combine and fix DNA probe, and then employ target DNA which is marked with biotin to combine GNPs by Biotin - Streptavidin combining. The simulation results show that this biochip can detect biological samples fast, high throughput, low cost, high sensitivity and reliably.

Abstract: Electroporation through nanochannels has potential as a useful tool for cell transfection. This potential is due to: the low voltage required; the centralized distribution of the potential penetration; the fact that this method causes no harm to the cell membrane, and; the even expression pattern of the target gene after electroporation. Additionally, the stable production process and improved yield rate can reduce the cost of producing the nanochannels and thus make the commercialization of this technique more feasible. This study aims to investigate the relationship between the speed of DNA stretching and the yield rate of nanochannels. We found that when the length of nanochannels is 2 µm, the yield rate can exceed 90% at a stretching speed of 2.3 mm/s . With a similarly high yield rate, longer nanochannels (3 µm) displayed a wider range of stretching speed. We have determined that the stretching speed can influence the adhesion of DNA and the subsequent fabrication of nanochannels. Therefore, this speed must be appropriately controlled.

Abstract: An electronic detection method for DNA molecules based on an extended gate field effect transistor (EGFET) sensing chip has been presented in this paper, which consists of one gold plate electrode for molecule recognition and FET part for signal transduction. The DNA probe was prepared by first immobilization of a thiolated single-stranded oligonucleotide (T1) and then an alkanethiol such as 6-hydroxy-1-hexanethiol (6-HHT) on the gold plate. A fast cyclic voltammetry (FCV) was applied to quantification of DNA molecules by using a cathodic peak around -1.3 V at a electrode reaction, corresponding to reductive desorption in strong alkali solution. By using a 70.7 mV DC voltage onto a Ag/AgCl reference electrode, the electronic signals of EGFET were applied to detection of DNA molecules and its hybridization, and the corresponding hybridization efficient was estimated to be about 37.5%. About 1 ~ 4 DNA molecules per 100 nm² on the Au substrate of EGFET could be counted, showing a promising sensing technique for bio-molecule.

Abstract: A kind of array micro-electromechanical systems (MEMS) cantilever of biochip is designed, which integrated capacitive pressure sensor. Before and after hybridization reaction, by the change of capacitance value, it can measure the capacitance values through integrated circuit (IC) to judge whether the solution containing the cantilever probe genes. In order to improve the detection sensitivity, it aggravate cantilever by gold nanoparticles combining hybridization information, applying Au-S chemical bond of gold nanoparticles and dithiol HS(CH2)6SH to combine and fix DNA probes and applying target DNA marked with biotin to combine gold nanoparticles by Biotin - Streptavidin combining. The results shows that this biochip can detect biological samples fast, high throughput, low cost, high sensitivity and reliably.

Abstract: A kind of array micro-electromechanical systems (MEMS) cantilever of biochip is designed, which piezoelectric devices drive MEMS cantilever resonance. Before and after hybridization reaction, by the change of the resonant frequency of the cantilever, it can detect the cantilever amplitude through optical detector to judge whether the solution containing the cantilever probe genes. In order to improve detection sensitivity, it aggravate cantilever by gold nanoparticles combining hybridization information, applying Au-S chemical bond of gold nanoparticles and dithiol HS(CH2)6SH to combine and fix DNA probe and applying target DNA marked with biotin to combine gold nanoparticles by Biotin - Streptavidin combining. The results shows that this biochip can detect biological samples fast, high throughput, low cost, high sensitivity and reliably.

Abstract: An extended gate field effect transistor (EGFET) sensing chip has been constructed by using one gold plate electrode for molecule recognition and FET part for signal transduction. By using a 70.7mV DC voltage onto a Ag/AgCl reference electrode, the electrical characteristics of immobilization of the oligonucleotide probe of P1 and hybridization with the target single strand DNA of P2 on the EGFET sensing chip were examined in detail. The electrical signals on the change of a threshold voltage (VT) shift at a constant ID (3000μA) in VG-ID characteristic were obtained, and the VT shift value due to hybridization was calculated to be 12 mV, which may be attributed to the decreased negative charges after hybridization occurred at the gate surface. The surface density of hybridized dsDNA on gold surface of the FET was evaluated to be about 1 × 1012 molecules/cm2, indicating that the EGFET was a promising sensing element for biochip.

Abstract: Biochip is an emerging technology and has evoked great research interests in recent years. In this paper, a novel air-driven loop-type microfluidic biochip was investigated. Differing from conventional micro channels, this chip has a micro loop-channel and 3 sets of driving conduits with valveless design in their intersections so that the microfluid can be driven smoothly in unidirectional circular movements. The driving efficiency reaches the highest if the entry angle of driving conduits is in the tangent direction of the loop-channel. However, the smaller the included angle, the impact area the larger, leading to comparatively serious reflow phenomenon. Furthermore, the microfluid can be controlled to stop almost instantaneously in the loop segment. Therefore, this loop-type biochip is suitable for biochemical reactions under repeated multiple temperature operations such as polymerase chain reaction. A full circular movement completes a cycle of PCR amplification. Besides, this biochip has its merits including simpler chip design, shorter channel length, and flexible controllability for biochemical reactions.