ZnO naorods on ZnO-coated seed substrates were fabricated by solution chemical method from Zn(NO3... more ZnO naorods on ZnO-coated seed substrates were fabricated by solution chemical method from Zn(NO3)2/NaOH under assisted electrical field. The working mechanism of electrical field was analyzed and the factors affecting the rod growth such as potential, precursor concentration and growth temperature were elucidated. The structural and optical properties are characterized by SEM, TEM, XRD, HRTEM and UV–vis. The results indicated that the nanorods have wurtzite structure without electrical field and are primarily of zincite structure under electrical field; when the electrical field is 1.1–1.3 V, not only the elevation of ion diffusion and adsorption lower the crystallite/solution interfacial energy and then the crystal nucleation barrier by increasing charge intensity, but also the production of H+ through oxidation of OH− increases properly the degree of solution supersaturation near the substrate, and thus lowers the activation energy. Both the two processes do favor to rod growth. With increasing precursor concentration in this system, the average diameter and length of ZnO nanorods increase, leading to decreasing of optical transmittance. The maximum rod growth rate at given concentration of Zn2+ occurs at a specific temperature.
International Journal of Rock Mechanics and Mining Sciences, 2000
A micromechanics-based model is used to study the mechanical properties of a granite under dynami... more A micromechanics-based model is used to study the mechanical properties of a granite under dynamic uniaxial compressive loads. The model is based on interacting sliding cracks uniformly distributed in the rock material. A dynamic crack growth criterion, which is related to crack growth velocity and dynamic fracture toughness of the rock material, is employed in the analysis. Under dynamic loads at strain rates from 10−4 to 100 s−1, the crack growth velocity is small compared to the critical crack growth velocity and the effect can be ignored. The strengths of the granite obtained by micromechanical modelling agree with the experimental results. A constitutive relation of the granite is derived from the energy equilibrium equation and correlated with the experimental results.
ABSTRACT Flexible and printable electronics are attractive techniques which have potential for br... more ABSTRACT Flexible and printable electronics are attractive techniques which have potential for broad applications not only in flexible but also in large area electronics. An effective and convenient method of fabricating high-resolution copper patterns with high conductivity and strong adhesion on flexible photopaper is demonstrated in this paper. Functional photopaper was prepared with inkjet printing of a palladium salt solution onto its surface, followed by electroless deposition of copper. Parameters of the printing process, such as voltage control waveform, temperature of printhead and substrate, meniscus vacuum level, printing height, etc. were optimized to obtain a robust and high resolution printing with feature dimensions down to 50 μm. Through a unique thermal sintering process, printed copper lines showed excellent conductivity of up to 3.9 × 107 S m−1 (>65% of bulk copper). The developed technique was successfully applied for fabricating paper based functional flexible circuits such as RFID antennae, micro-inductive coils and complex circuit boards.
ABSTRACT This paper describes a standard replication approach for preparing transparent elastomer... more ABSTRACT This paper describes a standard replication approach for preparing transparent elastomeric conductors with single-walled carbon nanotubes (SWCNTs) inlaid just below the surface. The elastic conductors were fabricated by spray coating a SWCNT suspension in chloroform on a fluorinated substrate, followed by the standard replication, casting liquid elastomers like polydimethylsiloxane on the SWCNT film, curing and peeling off the substrate. The replication strategy can produce elastic conductors with a flat or a desirable patterned surface. The resultant elastic conductors had excellent stability under repeated mechanical loading and stretchability up to 300%. It retained conductance even after 10 tape tests. Using the SWCNT-inlaid stretchable conductors as electrodes, elastic capacitors were fabricated using a mask-assisted method. The results showed that these capacitors are good candidates for multi-functional capacitive pressure, strain, and touch sensors.
2010 Symposium on Photonics and Optoelectronics, 2010
AbstractThis paper presents about the design and fabrication of a cost effective and portable sy... more AbstractThis paper presents about the design and fabrication of a cost effective and portable system for real time monitoring and data analysis of cell cultivation applications based on CMOS sensor and microfluidic technology. The digital CMOS sensor has 2-Mpixel resolution and ...
Blood analyses are the most common clinical diagnostic methods. Lab-on-a-chip technology, stemmed... more Blood analyses are the most common clinical diagnostic methods. Lab-on-a-chip technology, stemmed from concepts of microsystem microfabrication and microfluidics, provides an automatic, rapid, cost-effective and point-of-care solution for a wide variety of blood analyses. In general, blood separation is the first step for subsequent blood tests in clinical diagnosis. In this study, a rapid prototyping of out-of-plane valves using low cost tygon tubing is introduced to centrifugal system. With novel design of the out-of-plane valves, such Lab-in-a-tubing centrifugal systems can easily separate raw blood into blood cells and plasma. The out-of-plane valve has shown excellent capability in preventing backflow or reverse mixing due to diffusion. In addition, using tygon tubing is an easy, robust and inexpensive means to configure 3D microchannel networks, which is a fast proof-of-concept approach for the design of Lab-on-a-chip devices. At the end, this paper also presents a photolithographic microfabrication process for mass production of 3D Lab-on-a-CD microfluidic devices.
Journal of Micromechanics and Microengineering, 2010
The emergence of lab-on-a-CD technology provides a centrifugal and compact platform for high thro... more The emergence of lab-on-a-CD technology provides a centrifugal and compact platform for high throughput blood analysis in point-of-care (POC) diagnostics. Blood separation of the whole blood is the first step for clinical blood diagnosis. This paper describes a novel design of an out-of-plane microvalve that enables high performance of whole blood separation on lab-on-a-CD centrifugal devices. In our lab-on-a-CD design, blood cells and plasma are redistributed into a downstream sedimentation reservoir and an upstream supernatant reservoir, respectively, when the device spins. By tuning the rotational speed, the 'close' or 'open' status of an out-of-plane microvalve embedded in the lab-on-a-CD device is controlled to isolate these two reservoirs. Compared with a similar design but without the out-of-plane microvalve, this novel microvalve structure can effectively prevent blood cells from diffusing back to the supernatant reservoir containing pure plasma, and thus improve the performance of blood separation as well as subsequent blood analysis. We demonstrate that the lab-on-a-CD device with out-of-plane microvalves can achieve 99.9% plasma purity and 96 ± 0.5% plasma yield for the whole blood. Because of its simple structure and easily controlled working mechanism, the out-of-plane microvalve not only leads to high performance of whole blood separation, but also makes the manufacturing of this type of lab-on-a-CD device easy and inexpensive. If integrated into some existing lab-on-a-CD devices, the out-of-plane microvalve may also help improve their performance.
To improve the limit of detection in a nanoplasmonic sensor system, the optical performance of th... more To improve the limit of detection in a nanoplasmonic sensor system, the optical performance of the metal nanostructures should be optimized according to the best spectral window of the measurement instrument. We propose that the spectral window from 1460 to 1610 nm can potentially provide ultrahigh instrumental resolution for biosensing. We optimized gold nanoring arrays such that the extinction peak position is inside the proposed window, the extinction peak is sharp enough to track the peak shift with high resolution and the figure of merit (sensitivity/linewidth) of the array is optimized at the same time. The peak-sharpening effect of the array caused by coherent interaction plays a central role in the optimization. The optimized array has a lattice constant in the range [1000 nm,1060 nm], a bulk index sensitivity of around 450 nm/RIU and a figure of merit larger than 4. It is an enabling sensor element for a near-infrared sensor chip with ultrahigh resolution.
Lab-on-a-CD, as a main branch of Lab-on-a-chip technology, has led to several very successful com... more Lab-on-a-CD, as a main branch of Lab-on-a-chip technology, has led to several very successful commercial products. Most of these existing Lab-on-a-CD systems present complex system designs and thus are relatively expensive. In this work, we have developed a simple but robust Lab-on-a-CD system for parallel whole blood analyses. This Lab-on-a-CD system incorporates electrochemical bioanalysis and a simple blood sample separation mechanism into the centrifugal platform, and thus reduces the system's complexity. To demonstrate the applicability, the system was applied to perform basic metabolic panel tests, for example, the concentrations of glucose, lactate and uric acids of whole blood samples. Using only 16 μL of whole blood, within a few minutes, the Lab-on-a-CD system could produce results that agreed in general with the data by a conventional system. Therefore, this proof-of-concept Lab-on-a-CD system has demonstrated the potential to become a robust and simple-to-use device for parallel blood analyses.
This paper presents about the design and fabrication of a cost effective and portable system for ... more This paper presents about the design and fabrication of a cost effective and portable system for real time monitoring and data analysis of cell cultivation applications based on CMOS sensor and microfluidic technology. The digital CMOS sensor has 2-Mpixel resolution and output digital data that is designed and fabricated on the 0.18um CMOS image process. The Chip has integrated with low noise 2 shared 2.25T pinned photodiode active pixel, noise reduction circuit, analog to digital converter and timing control circuits. The module based on the 2-Mpixel CMOS sensor has two focuses that can capture the image of the business card so that the monitoring system is so compact and low power. In this paper, one microfluidic product has been fabricated based on the MEMS process that applies for cell cultivation. The online monitoring and analytical system uses CMOS image sensor to capture the image of the microfluidic applications and a field programmable gate array (FPGA) chip to process the captured image. The final image can be displayed in the monitor or be sent to computer to be stored. This technique can be utilized in monitoring the cell size lying on the pixel size of CMOS sensor. In this paper, the monitoring cell size is large than 2.8um for the pixel size of CMOS sensor is 2.8um. The advantages of this system not only provide miniaturization and minimum cost, but also offer many advantages over conventional laboratory experiments, such as low energy LED light, parallel and fast microfluidic chip, high resolution CMOS sensor, fast and accurate test, low cost and consumption, etc.
ZnO naorods on ZnO-coated seed substrates were fabricated by solution chemical method from Zn(NO3... more ZnO naorods on ZnO-coated seed substrates were fabricated by solution chemical method from Zn(NO3)2/NaOH under assisted electrical field. The working mechanism of electrical field was analyzed and the factors affecting the rod growth such as potential, precursor concentration and growth temperature were elucidated. The structural and optical properties are characterized by SEM, TEM, XRD, HRTEM and UV–vis. The results indicated that the nanorods have wurtzite structure without electrical field and are primarily of zincite structure under electrical field; when the electrical field is 1.1–1.3 V, not only the elevation of ion diffusion and adsorption lower the crystallite/solution interfacial energy and then the crystal nucleation barrier by increasing charge intensity, but also the production of H+ through oxidation of OH− increases properly the degree of solution supersaturation near the substrate, and thus lowers the activation energy. Both the two processes do favor to rod growth. With increasing precursor concentration in this system, the average diameter and length of ZnO nanorods increase, leading to decreasing of optical transmittance. The maximum rod growth rate at given concentration of Zn2+ occurs at a specific temperature.
International Journal of Rock Mechanics and Mining Sciences, 2000
A micromechanics-based model is used to study the mechanical properties of a granite under dynami... more A micromechanics-based model is used to study the mechanical properties of a granite under dynamic uniaxial compressive loads. The model is based on interacting sliding cracks uniformly distributed in the rock material. A dynamic crack growth criterion, which is related to crack growth velocity and dynamic fracture toughness of the rock material, is employed in the analysis. Under dynamic loads at strain rates from 10−4 to 100 s−1, the crack growth velocity is small compared to the critical crack growth velocity and the effect can be ignored. The strengths of the granite obtained by micromechanical modelling agree with the experimental results. A constitutive relation of the granite is derived from the energy equilibrium equation and correlated with the experimental results.
ABSTRACT Flexible and printable electronics are attractive techniques which have potential for br... more ABSTRACT Flexible and printable electronics are attractive techniques which have potential for broad applications not only in flexible but also in large area electronics. An effective and convenient method of fabricating high-resolution copper patterns with high conductivity and strong adhesion on flexible photopaper is demonstrated in this paper. Functional photopaper was prepared with inkjet printing of a palladium salt solution onto its surface, followed by electroless deposition of copper. Parameters of the printing process, such as voltage control waveform, temperature of printhead and substrate, meniscus vacuum level, printing height, etc. were optimized to obtain a robust and high resolution printing with feature dimensions down to 50 μm. Through a unique thermal sintering process, printed copper lines showed excellent conductivity of up to 3.9 × 107 S m−1 (>65% of bulk copper). The developed technique was successfully applied for fabricating paper based functional flexible circuits such as RFID antennae, micro-inductive coils and complex circuit boards.
ABSTRACT This paper describes a standard replication approach for preparing transparent elastomer... more ABSTRACT This paper describes a standard replication approach for preparing transparent elastomeric conductors with single-walled carbon nanotubes (SWCNTs) inlaid just below the surface. The elastic conductors were fabricated by spray coating a SWCNT suspension in chloroform on a fluorinated substrate, followed by the standard replication, casting liquid elastomers like polydimethylsiloxane on the SWCNT film, curing and peeling off the substrate. The replication strategy can produce elastic conductors with a flat or a desirable patterned surface. The resultant elastic conductors had excellent stability under repeated mechanical loading and stretchability up to 300%. It retained conductance even after 10 tape tests. Using the SWCNT-inlaid stretchable conductors as electrodes, elastic capacitors were fabricated using a mask-assisted method. The results showed that these capacitors are good candidates for multi-functional capacitive pressure, strain, and touch sensors.
2010 Symposium on Photonics and Optoelectronics, 2010
AbstractThis paper presents about the design and fabrication of a cost effective and portable sy... more AbstractThis paper presents about the design and fabrication of a cost effective and portable system for real time monitoring and data analysis of cell cultivation applications based on CMOS sensor and microfluidic technology. The digital CMOS sensor has 2-Mpixel resolution and ...
Blood analyses are the most common clinical diagnostic methods. Lab-on-a-chip technology, stemmed... more Blood analyses are the most common clinical diagnostic methods. Lab-on-a-chip technology, stemmed from concepts of microsystem microfabrication and microfluidics, provides an automatic, rapid, cost-effective and point-of-care solution for a wide variety of blood analyses. In general, blood separation is the first step for subsequent blood tests in clinical diagnosis. In this study, a rapid prototyping of out-of-plane valves using low cost tygon tubing is introduced to centrifugal system. With novel design of the out-of-plane valves, such Lab-in-a-tubing centrifugal systems can easily separate raw blood into blood cells and plasma. The out-of-plane valve has shown excellent capability in preventing backflow or reverse mixing due to diffusion. In addition, using tygon tubing is an easy, robust and inexpensive means to configure 3D microchannel networks, which is a fast proof-of-concept approach for the design of Lab-on-a-chip devices. At the end, this paper also presents a photolithographic microfabrication process for mass production of 3D Lab-on-a-CD microfluidic devices.
Journal of Micromechanics and Microengineering, 2010
The emergence of lab-on-a-CD technology provides a centrifugal and compact platform for high thro... more The emergence of lab-on-a-CD technology provides a centrifugal and compact platform for high throughput blood analysis in point-of-care (POC) diagnostics. Blood separation of the whole blood is the first step for clinical blood diagnosis. This paper describes a novel design of an out-of-plane microvalve that enables high performance of whole blood separation on lab-on-a-CD centrifugal devices. In our lab-on-a-CD design, blood cells and plasma are redistributed into a downstream sedimentation reservoir and an upstream supernatant reservoir, respectively, when the device spins. By tuning the rotational speed, the 'close' or 'open' status of an out-of-plane microvalve embedded in the lab-on-a-CD device is controlled to isolate these two reservoirs. Compared with a similar design but without the out-of-plane microvalve, this novel microvalve structure can effectively prevent blood cells from diffusing back to the supernatant reservoir containing pure plasma, and thus improve the performance of blood separation as well as subsequent blood analysis. We demonstrate that the lab-on-a-CD device with out-of-plane microvalves can achieve 99.9% plasma purity and 96 ± 0.5% plasma yield for the whole blood. Because of its simple structure and easily controlled working mechanism, the out-of-plane microvalve not only leads to high performance of whole blood separation, but also makes the manufacturing of this type of lab-on-a-CD device easy and inexpensive. If integrated into some existing lab-on-a-CD devices, the out-of-plane microvalve may also help improve their performance.
To improve the limit of detection in a nanoplasmonic sensor system, the optical performance of th... more To improve the limit of detection in a nanoplasmonic sensor system, the optical performance of the metal nanostructures should be optimized according to the best spectral window of the measurement instrument. We propose that the spectral window from 1460 to 1610 nm can potentially provide ultrahigh instrumental resolution for biosensing. We optimized gold nanoring arrays such that the extinction peak position is inside the proposed window, the extinction peak is sharp enough to track the peak shift with high resolution and the figure of merit (sensitivity/linewidth) of the array is optimized at the same time. The peak-sharpening effect of the array caused by coherent interaction plays a central role in the optimization. The optimized array has a lattice constant in the range [1000 nm,1060 nm], a bulk index sensitivity of around 450 nm/RIU and a figure of merit larger than 4. It is an enabling sensor element for a near-infrared sensor chip with ultrahigh resolution.
Lab-on-a-CD, as a main branch of Lab-on-a-chip technology, has led to several very successful com... more Lab-on-a-CD, as a main branch of Lab-on-a-chip technology, has led to several very successful commercial products. Most of these existing Lab-on-a-CD systems present complex system designs and thus are relatively expensive. In this work, we have developed a simple but robust Lab-on-a-CD system for parallel whole blood analyses. This Lab-on-a-CD system incorporates electrochemical bioanalysis and a simple blood sample separation mechanism into the centrifugal platform, and thus reduces the system's complexity. To demonstrate the applicability, the system was applied to perform basic metabolic panel tests, for example, the concentrations of glucose, lactate and uric acids of whole blood samples. Using only 16 μL of whole blood, within a few minutes, the Lab-on-a-CD system could produce results that agreed in general with the data by a conventional system. Therefore, this proof-of-concept Lab-on-a-CD system has demonstrated the potential to become a robust and simple-to-use device for parallel blood analyses.
This paper presents about the design and fabrication of a cost effective and portable system for ... more This paper presents about the design and fabrication of a cost effective and portable system for real time monitoring and data analysis of cell cultivation applications based on CMOS sensor and microfluidic technology. The digital CMOS sensor has 2-Mpixel resolution and output digital data that is designed and fabricated on the 0.18um CMOS image process. The Chip has integrated with low noise 2 shared 2.25T pinned photodiode active pixel, noise reduction circuit, analog to digital converter and timing control circuits. The module based on the 2-Mpixel CMOS sensor has two focuses that can capture the image of the business card so that the monitoring system is so compact and low power. In this paper, one microfluidic product has been fabricated based on the MEMS process that applies for cell cultivation. The online monitoring and analytical system uses CMOS image sensor to capture the image of the microfluidic applications and a field programmable gate array (FPGA) chip to process the captured image. The final image can be displayed in the monitor or be sent to computer to be stored. This technique can be utilized in monitoring the cell size lying on the pixel size of CMOS sensor. In this paper, the monitoring cell size is large than 2.8um for the pixel size of CMOS sensor is 2.8um. The advantages of this system not only provide miniaturization and minimum cost, but also offer many advantages over conventional laboratory experiments, such as low energy LED light, parallel and fast microfluidic chip, high resolution CMOS sensor, fast and accurate test, low cost and consumption, etc.
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