No abstract

Throughout the course of one day, the human body goes through numerous mechanical activities. These activities, while usually not very powerful individually, produce an ample amount of energy collectively. This mechanical energy can be harvested into electrical energy via piezoelectricity. Recent research into piezoelectric nanocomposites has yielded techniques to foam the materials into softer, porous structures more suitable for human comfort. This study focuses on using a host polymer polydimethylsiloxane (PDMS) and citric acid to create foams. Citric acid, a common industrial chemical blowing agent (CBA), is used in this project due to its capabilities to produce foams with consistent pore sizes and distribution. These foams, coupled with piezoelectric nanoparticles, are fabricated, analyze, and tested. They are mechanically characterized using tensile testing. Electrical characterization is carried out using an integrated mechanical-electrical testing setup. These foams are lighter, softer, and can produce higher electrical output than non-porous counterparts. We believe that these foams have great potential in upcoming piezoelectric technology.

A common method to precisely control the material properties is to evenly distribute functional nanomaterials within the substrate. For example, it is possible to mix a silk solution and nanomaterials together to form one tuned silk sample. However, the nanomaterials are likely to aggregate in the traditional manual mixing processes. Here we report a pilot study of utilizing specific microfluidic mixing designs to achieve a uniform nanomaterial distribution with minimal aggregation. Mixing patterns are created based on classic designs and then validated by experimental results. The devices are fabricated on polydimethylsiloxane (PDMS) using 3D printed molds and soft lithography for rapid replication. The initial mixing performance is validated through the mixing of two solutions with colored dyes. The microfluidic mixer designs are further analyzed by creating silk-based film samples. The cured film is inspected with scanning electron microscopy (SEM) to reveal the distribution uniformity of the dye particles within the silk material matrix. Our preliminary results show that the microfluidic mixing produces uniform distribution of dye particles. Because the microfluidic device can be used as a continuous mixing tool, we believe it will provide a powerful platform for better preparation of silk materials. By using different types of nanomaterials such as graphite (demonstrated in this study), graphene, carbon nanotubes, and magnetic nanoparticles, the resulting silk samples can be fine-tuned with desired electrical, mechanical, and magnetic properties.

The unique physical and structural properties of carbon nanotubes (CNTs) have made them a powerful sensing material. CNTs exhibit excellent adsorption capabilities due to their large surface area and available bonding sites for other molecules. There has been increasing interest in using CNT-based sensors for food safety control based upon accurate detection of foodborne threats. These sensors can replace, or at least serve as a powerful alternative to, the existing sensing systems that often suffer from low sensitivity, poor specificity, low detection limit, long detection time and high costs. Here we provide a critical review on CNT sensors and their applications in food safety and quality analysis. Due to the wide variety of potential substances, the sensors are divided into different groups based upon the materials under detection. The critical information such as the sensor designs, sensing principles, material preparation processes and sensing experiments are summarized and discussed. The increased accuracy and effectiveness have made CNTs a promising sensing material for low-cost, portable and powerful sensors. With the intensive and continuous research in this field, it is anticipated that these sensors will become increasingly more useful in the food industry.