Development of microcantilever biosensing platforms

Microcantilever sensor system as a promising field attracted much attention recently. This system has the potential to be applied for a biosensing technology which is parallel reference, label free, sensitive and real time. In this thesis, polyimide has been selected as a material to fabricate cantilever due to its excellent physical, electrical and mechanical properties, on top of its cost advantage. Importantly, we showed it is feasible to microfabricate large array of microcantilever sensors with high-power UV laser directly. It is low cost and rapid, the parameters for laser direct writing fabrication has been studied. The thesis also shows that it is possible to functionalise the polyimide film first and subsequently cut it to functionalised cantilever sensor array. The unique fabrication and functionalisation process can solve the problem of high-cost microfabrication using silicon and low-efficient functionalisation using capillary tubing all together. In addition, the fabrication process has been further developed to avoid the problem of the cross contamination from receptors on both sides. With this improvement, we developed an internally referenced microcantilever biosensors system for DNA hybridization detection. Different receptors can be coated on each side of the polymer film before fabricating to cantilever biosensors This newly developed capability enables us to coat receptors with similar but slightly different biological properties on each side of the cantilever sensor, a process which is extremely difficult by using conventional capillary tubing methods due to the possibility of thiol exchange on surfaces and hence cross-contamination. A polyimide microcantilever sensor with embedded microfluidic channel has been developed in this thesis. Photoresist material is used to form the precise microfluidic channel within the microcantilever device. The multilayer polymer film device is still soft enough to operate in static mode. The main advantage of the system presented here is that since the device is made entirely of polymer materials, the fabrication process is simple and low-cost. The magnetic beads have been used to amplify the signal of the biosensing processing; the application of polyimide microfluidic microcantilevers to the detection of Cryptosporidium and thrombin is reported in this thesis. Paper based autonomous micocantilever system has also been investigated in this thesis. We build a cantilever system without external pump or force with paper and magnetic field. The limitation of the system is that it takes too much time to pump magnetic beads through the cantilever with capillary. However, we found that it has the potential to develop a long time range timer based on the slowest property. Different methods have been investigated to slow down the speed, when liquid pass through the paper microfluidic. Finally, we demonstrate some timer devices whose ranges are from minutes to month. The devices have the potential to be used as time-based diagnostic assays, food label, etc

An Empirical Study on the Change of Consumption Level of Chinese Residents

With the rapid development of Chinese economy since the reform and opening up, people's living standards have been improved, and people's consumption level has been gradually improved. Consumption plays an important role in stimulating economic growth. At present, China needs to adjust its economic structure and optimize its industrial structure. Therefore, it is very important to analyze the factors that affect the consumption level of Chinese residents and study the main factors for promoting the healthy and sustainable development of Chinese economy. Therefore, based on the statistical data from 1995 to 2018, this paper collects the variable data that affects the consumption level of residents, such as the freight volume of infrastructure railway and highway, the per capita disposable income of national residents, ordinary college students, the consumer  price index of residents, the average real wage index and the gross domestic product. And through the establishment of multiple linear regression model and the stepwise regression, the paper also finds out the main factors influencing the consumption level of residents. Using R language and analyzing the results of the research, we can draw the conclusion that the national per capita disposable income, ordinary college students and consumer price index and GDP are the main factors that affect the consumption level of Chine

An Empirical Study on Patient Queuing after Medical Staff Supporting Disaster Areas in Northwest China

Recently, the new coronavirus has brought great disaster to human beings, so we have to take strong measures to suppress the large-scale outbreak of the disease. In this paper, by looking up the data of medical staff supporting Wuhan area in Northwest China, we build a queuing model of  to analyze the waiting time and staying time of patients. Secondly, due to the increase of patients, the burden of outpatient service is gradually increasing, which leads to the speed of epidemic spread greatly accelerated. Therefore,  model is constructed to analyze the relationship between patients and healers. The experimental results show that: (1) at the beginning of the data of more than 1000 medical staff, the patients were served for too long, which led to low efficiency. When they were supported, the efficiency was increasing with the increase of support, and the time was shortened, which was very helpful to relieve the medical pressure of outpatient. (2) With the increase of patients, at the same time, the number of healers is increasing, of course, there are also healthy people in it. At this time, we should focus on finding a suitable node, reducing the number of patients and increasing the number of healers, so as to effectively control the epidemic

Comparative Research on Air Conditioner with Gas-injected Rotary Compressor through Injection Port on Blade

Rotary compressors are widely utilized in air conditionders and heat pumps. However, when rotary compressors were applied in room air conditioners, VRFs and domestic water heaters, the systems will experience heavily degradation of the heating capacity and COP as the ambient temperature goes low. Aimed at these problems, considerable research has been carried out to raise a series of solutions, such as economizer technology, cascade-type vapor compression heat pump system and two stage coupling heat pump system. At present, economizer technology has become a critical method to improve the performance of air source heat pumps with rotary compressors in low ambient temperature. A novel vapor injection structure on a blade for a rotary compressor has been proposed in previous paper to overcome the drawback of the traditional cylinder injection structure. Based on a verified numerical model, the performance of air source heat pumps with rotary compressors with different economizer technology including a two-stage rotary compressor, a single-stage rotary compressor with traditional injection structure and a single rotary compressor with the novel injection structure has been investigated. The results indicate that: compared to rotary compressors with traditional injection structure, air source heat pump with a rotary compressor with proposed injection structure can enhance the heating capacity and COP by 13%~15% and 4.8%~9.6%, respectively; and compared to the twin-cylinder rotary compressor, the performance of air source heat pump with a rotary compressor with proposed injection structure is almost the same, so the rotary compressor with the novel injection structure could be considered to replace the two-stage rotary compressor

A Novel Vapor Injection Structure on the Blade for Rotary Compressor

Rotary compressors have been extensively used in room air conditioners and household refrigerators for their advantages, including high efficiency, strong adaptability, and low cost. However, when air source heat pumps with rotary compressors are applied in cold regions, a series of problems appear. The gas injection has been proved an effective technology to enhance both the heating capacity and COP of scroll, screw, and rotary compressors. In the one-cylinder rotary compressor with gas injection, the compressor injection port is often opened on the cylinder wall. In order to extend the injection time for injecting more refrigerant, the injection port is settled as close as possible to the discharge port. However, the limited area of the injection port and the unavoidable back-flowing of the injection refrigerant into the suction tube diminish the merits of gas injection on the one-cylinder rotary compressor. A novel vapor injection structure on the blade for the rotary compressor has been proposed in this paper to overcome the back-flowing drawback of the traditional cylinder injection structure and increase the injection area. Based on a verified numerical model, the performance of a rotary compressor with the blade injection structure has been investigated. The results indicate that: the proposed vapor injection structure can eliminate the back-flowing of the injected refrigerant; compared to the traditional injection structure, the new structure can enhance the volumetric efficiency and mass flow-rate by 1.8~2.7% and 26.6~57.2%, respectively; and compared to the traditional injection structure, the new structure can increase the heating capacity and COP by 23.1~48.9% and 3.2~8.0%, respectively

High photo-excited carrier multiplication by charged InAs dots in AlAs/GaAs/AlAs resonant tunneling diode

We present an approach for the highly sensitive photon detection based on the quantum dots (QDs) operating at temperature of 77K. The detection structure is based on an AlAs/GaAs/AlAs double barrier resonant tunneling diode combined with a layer of self-assembled InAs QDs (QD-RTD). A photon rate of 115 photons per second had induced 10nA photocurrent in this structure, corresponding to the photo-excited carrier multiplication factor of 10^7. This high multiplication factor is achieved by the quantum dot induced memory effect and the resonant tunneling tuning effect of QD-RTD structure.Comment: 10 pages,5 figures. Submitted to Applied Physics Letter

Effects of Economizer Type and Size to the Gas Injected System Using Zeotropic R32/R1234ze(E) Mixture

Refrigerant mixtures are commonly regarded as a potential substitute because rare pure refrigerants can totally meet all the requirements of environmental, thermodynamic and safe properties. Meanwhile as an effective means, vapour injection is widely applied to improve the system performance of heat pump under large pressure ratio. However, the difference of using pure refrigerant and refrigerant mixtures, which configuration of vapour injection is more suitable for refrigerant mixtures are still unclear. In this paper, R32/R1234ze(E) mixtures are chosen as refrigerant pairs for its great potential in the future, and the scroll compressor is chosen as well to carry out the research for its wide application in vapour injected system. The thermodynamic model with different suction and injected concentration is derived, on the basis of this model, a detailed compressor and system performance comparison of different vapour injected configurations with R32/R1234ze(E) mixtures are investigated. The results indicate that the lower concentration of R32 in flash tank (FT) system will result in higher power consumption compared with intermediate heat exchanger (IHX) system. For the system performance, the heating capacity of FT system is 5%~9.1% higher than IHX system, while the COP of latter system is usually higher, the largest improvement is 2.7% when charged with R32/R1234ze(E) (40/60) mixtures

Seasonal Applicability of Refrigerant Release Technology in Room Air Conditioner

The room air conditioner is widely used in residential and office buildings for both cooling and heating. However, the operation condition of the room air conditioner changes largely due to the variations of the cooling/heating load of the room, the indoor temperature and the outdoor one, which always decreases the efficiency of the compressor and eventually the seasonal energy efficiency of the air conditioner. The refrigerant release technology relieves even eliminates the over-compression loss of scroll compressor by bypassing the refrigerant in the compression chamber to the suction pipe under small system pressure ratio conditions, By using it, the efficiency of the air conditioner can be increased. The effect of refrigerant-releasing on the annual energy performance of the room air conditioner is analyzed and the applicability is evaluated in this paper. The typical residential and office building models are built in a building load simulation software, DeST. The annual cooling and heating loads of these buildings located in different climate zones are calculated. The numerical models of the fixed speed and inverter room air conditioners with and without refrigerant-releasing function are built and verified. For the air conditioner with refrigerant-releasing, a control strategy to activate the refrigerant release is determined to keep the efficiency as well as satisfy the indoor load. Based on the calculated cooling/heating load and the models of the air conditioners, the energy consumptions of all four kinds of air conditioner during each hour can be calculated. Finally, the performance of variable and fixed speed air conditioner with and without refrigerant release in the cooling period and heating period is obtained and the contribution of refrigerant-releasing is evaluated. The results show that the variable speed air conditioner with refrigerant-releasing saves 24.2~25.5% and 18.9~25.3% energy compared to the one without refrigerant release for the office and residential buildings, respectively. For the fixed speed air conditioner, the refrigerant-releasing technology decreases 20.2~23.0% and 17.1~23.6% energy consumption for residential and office building, respectively. Variable speed air conditioner with refrigerant release saves more energy than fixed speed one. The refrigerant-releasing technology has good applicability for the room air conditioner and should be considered as an effective method to enhance the seasonal performance for it