Radio Frequency Micro/Nano-Fluidic Devices for Microwave Dielectric Property Characterizations

In this dissertation, a number of different topics in microwave dielectric property measurements have been covered by a systematic approach to the goals of development of dielectric spectroscopy and study of its high electric field effects with integrated on-chip microwave microfluidic / nanofluidic devices. A method of parasitic effects cancellation for dielectric property measurement is proposed, analyzed, and experimentally evaluated for microwave characterization of small devices and materials that yield low intensity signals. The method dramatically reduces parasitic effects to uncover the otherwise buried signals. A high-sensitive radio frequency (RF) device is then developed and fabricated to detect small dielectric property changes in microfluidic channel. Sensitivity improvement via on-chip transmission line loss compensation is then analyzed and experimentally demonstrated. Different samples are measured and high sensitivity is achieved compared to conventional transmission-line-based methods. High DC electric field effects on dielectric properties of water are investigated with microwave microfluidic devices. Gold microstrip-line-based devices and highly-doped silicon microstrip-line-based devices are exploited. Initiation process of water breakdown in a small gap is discussed. Electrode surface roughness is examined and its effect on observed water breakdown is investigated. It is believed that electrode surface roughness is one of critical factors for the initiation process of water breakdown in small gap system. Finally, water dielectric property subjected to uniform DC electric field in 260 nm planar microfluidic channels is experimentally studied via silicon microstrip-line-based devices. When applied DC field is as high as up to ~ 1 MV/cm, the water is sustained and no breakdown is occurred. Strong water dielectric saturation effects are observed from measured water dielectric spectroscopy. An on-chip, broadband microwave dielectric spectrometer with integrated transmission line and nanofluidic channels is designed, fabricated and characterized through microwave S-parameter measurements. Heavily-doped Si material is used to build the microstrip line to provide broadband characterization capability. 10 nm deep planar Si nanofluidic channels are fabricated through native oxide etch and wafer bonding process. It is the first effort to build the microstrip line with periodically loaded individual sub-10 nm nanofluidic channels to conduct the broadband high frequency characterization of materials within confined space. The functionality of the device is demonstrated by the measurement of DI water. It behaves well and has great potentials on the study of confinement effects of fluids and molecules. Further work includes development of parasitic signal de-embedding procedures for accurate measurements

Dielectric Spectrometers with Planar Nanofluidic Channels

Disclosed is a method for fabricating nanofluidic channels having a height of from about 1 nm to about 10 nm. Generally, the method includes formation of doped silicon parallel strips in a silicon substrate, formation of a native oxide layer on the substrate, and etching of the native oxide layer at one of the strips to form a channel of a depth of between about 1 nm and about 10 nm. The method also includes bonding a second wafer to the surface, the second wafer including through etched windows to provide probe contacts to two of the parallel strips during use. These parallel strips provide high-frequency transmission lines in the device that can provide broadband dielectric spectroscopy measurement within the nanochannels

Microwave Dielectric Properties of On-Chip Liquid Films

A microwave characterization method for on-chip liquid film dielectric property measurement is developed. Microstrip-line based on-chip test structures are fabricated to characterize the microwave dielectric properties of various on-chip liquid films: DI water and binary mixtures of DI water with glucose and ethanol. The obtained microwave dielectric properties are presented in Cole-Cole diagrams, which show general frequency dependence similar to that of bulk liquids. Different concentration levels of glucose and ethanol show different microwave dielectric responses. Therefore, on-chip microwave dielectric spectroscopy provides a promising and inexpensive on-chip sensing mechanism for biomedical and chemical applications

The Effectiveness of Pay-It-Forward in Addressing HPV Vaccine Delay and Increasing Uptake Among 15–18-Year-Old Adolescent Girls Compared to User-Paid Vaccination: A Study Protocol for a Two-Arm Randomized Controlled Trial in China

Background Human papillomavirus (HPV) vaccination could prevent cervical and other HPV-associated cancers attributable to vaccine-associated HPV types. However, HPV vaccination coverage among women aged 9–18 years old is low in China. Common barriers include poor financial affordability, minimal public engagement, and low confidence in domestically produced HPV vaccines. Pay-it-forward offers an individual a free or subsidized service then an opportunity to voluntarily donate and/or create a postcard message to support future people. This study aims to assess the effectiveness of pay-it-forward as compared to standard-of-care self-paid vaccination to improve HPV vaccine uptake among adolescent girls aged 15–18 years, who are left out in the current pilot free HPV vaccination task force in some parts of China. Methods This is a two-arm randomized controlled trial in Chengdu, China. Eligible adolescent girls (via caregivers) will be randomly selected and recruited through four community health centers (one in the most developed urban areas, one in higher middle-income and one in lower middle-income suburban areas, and one in the least developed rural areas) using the resident registration list. A total of 320 participants will be randomized into two study arms (user-paid versus pay-it-forward vaccination) in a 1:1 ratio. The intervention assignment will be blinded to recruiters and participants using envelop concealment until the research assistants open the envelop to determine which treatment to deliver to each individual. The primary outcome of the study will be HPV vaccine uptake by administrative data. Secondary outcomes include costs, vaccine hesitancy, and the completion rates of the 3-dose HPV vaccination series. Discussion This study will investigate an innovative pay-it-forward strategy’s effectiveness and economic costs to improve HPV vaccination among 15–18-year-old adolescent girls. Study findings will have implications for increasing HPV vaccine uptake in places where HPV vaccines are provided for a fee

The Effect of Iron Oxide Magnetic Nanoparticles on Smooth Muscle Cells

Recently, magnetic nanoparticles of iron oxide (Fe3O4, γ-Fe2O3) have shown an increasing number of applications in the field of biomedicine, but some questions have been raised about the potential impact of these nanoparticles on the environment and human health. In this work, the three types of magnetic nanoparticles (DMSA-Fe2O3, APTS-Fe2O3, and GLU-Fe2O3) with the same crystal structure, magnetic properties, and size distribution was designed, prepared, and characterized by transmission electronic microscopy, powder X-ray diffraction, zeta potential analyzer, vibrating sample magnetometer, and Fourier transform Infrared spectroscopy. Then, we have investigated the effect of the three types of magnetic nanoparticles (DMSA-Fe2O3, APTS-Fe2O3, and GLU-Fe2O3) on smooth muscle cells (SMCs). Cellular uptake of nanoparticles by SMC displays the dose, the incubation time and surface property dependent patterns. Through the thin section TEM images, we observe that DMSA-Fe2O3is incorporated into the lysosome of SMCs. The magnetic nanoparticles have no inflammation impact, but decrease the viability of SMCs. The other questions about metabolism and other impacts will be the next subject of further studies

The effectiveness of pay-it-forward in addressing HPV vaccine delay and increasing uptake among 15-18-year-old adolescent girls compared to user-paid vaccination: a study protocol for a two-arm randomized controlled trial in China

BACKGROUND: Human papillomavirus (HPV) vaccination could prevent cervical and other HPV-associated cancers attributable to vaccine-associated HPV types. However, HPV vaccination coverage among women aged 9-18 years old is low in China. Common barriers include poor financial affordability, minimal public engagement, and low confidence in domestically produced HPV vaccines. Pay-it-forward offers an individual a free or subsidized service then an opportunity to voluntarily donate and/or create a postcard message to support future people. This study aims to assess the effectiveness of pay-it-forward as compared to standard-of-care self-paid vaccination to improve HPV vaccine uptake among adolescent girls aged 15-18 years, who are left out in the current pilot free HPV vaccination task force in some parts of China. METHODS: This is a two-arm randomized controlled trial in Chengdu, China. Eligible adolescent girls (via caregivers) will be randomly selected and recruited through four community health centers (one in the most developed urban areas, one in higher middle-income and one in lower middle-income suburban areas, and one in the least developed rural areas) using the resident registration list. A total of 320 participants will be randomized into two study arms (user-paid versus pay-it-forward vaccination) in a 1:1 ratio. The intervention assignment will be blinded to recruiters and participants using envelop concealment until the research assistants open the envelop to determine which treatment to deliver to each individual. The primary outcome of the study will be HPV vaccine uptake by administrative data. Secondary outcomes include costs, vaccine hesitancy, and the completion rates of the 3-dose HPV vaccination series. DISCUSSION: This study will investigate an innovative pay-it-forward strategy's effectiveness and economic costs to improve HPV vaccination among 15-18-year-old adolescent girls. Study findings will have implications for increasing HPV vaccine uptake in places where HPV vaccines are provided for a fee. TRIAL REGISTRATION: Chinese Clinical Trial Registry (ChiCTR), ChiCTR2200055542. Registered on 11 January 2022