Novel Nanomaterials and Performance Industrial Products, 2019

 

You-Lo Hsieh, distinguished professor, Dept. of Biological and Agricultural Engineering, UC Davis

The goal of this research is to develop efficient processes to isolate rice straw components and to convert them into new nanomaterials and advanced functional products. In 2019, work focused on expanding high-performance product development and technology transfer of existing rice straw nanotechnologies.

The most diverse array of nanocelluloses, including rod-like cellulose nanocrystals and super-thin and long cellulose nanofibrils with tunable surface chemistries and charges have been fabricated from rice straw cellulose. These are the most diverse assortment of nanocelluloses from a single source among agricultural biomass. They have potential applications as oil dispersants, antimicrobial agents, microbial coagulants, synthesis templates for nanoparticles, aqueous exfoliating agents for graphene, and nano-building blocks for a range of fibers, films, coatings, hydrogels, and aerogels.

Proof of concept has been demonstrated in applications of these advanced materials for oil-water separation, water purification, organic solvent/hydrocarbon removal or oil cleanup, films and coating technologies, conducting aerogels, strain sensor, CO2 capturing, thermal insulation, and moisture responsive nanopaper to name a few.

Technology transfer

One U.S. patent was filed in March 2019, one international patent application was filed in October 2019, and one new record of invention for provisional patent was filed in August 2019. Altogether, five total provisional patents, two each in 2017 and 2018, as well as one in 2019, have been filed in connection with this research.

To exploit potential products and applications from provisional patents, timely effort is critical to target more specific applications of the strong, wet resilient, and tunable aerogels. Three global companies and two startups have entered into confidential disclosure agreements and begun discussions on developing rice straw nanocellulose and nanosilica-based products. Four other inquiries of potential applications have led to discussions of technology development and transfer, including one on rice straw nanosilica gas absorbents and three on nanocellulose aerogels for health, automobile, and insulation applications.

Aerogel product development

Rice straw nanocellulose aerogels represent the most developed, advanced materials from rice straw, and have already reached a high level of technical readiness. Nanocellulose aerogels are super-absorbent of aqueous, as well as organic liquids. This amphiphilic attribute is so unique that it distinguishes rice straw nanocellulose aerogels from both the hydrophobic carbon and the hydrophilic silica aerogels--or those based on dissolved cellulose.

These nanocellulose aerogels have many unique attributes that differentiate them from commercially available aerogels. Shaping nanocellulose aerogels into desired forms and dimensions has targeted the most challenging engineered forms, such as fibers that can be fabricated into flexible mats and knitted, woven, and nonwoven wearable materials for thermal protective applications.

Highly porous and strong, cellulose-rich coaxial fibers have been successfully engineered as novel thermal insulation materials. A sheath containing multiscale pores on both inner and outer surfaces provided a protective surface layer for the cellulose nanofibril aerogel core.

These porous coaxial fibers have many desirable qualities, including low density, high porosity, high specific tensile strength, wide working temperature range, large-scale producibility, as well as biodegradability. The unique combination of multiscale porous sheath and ultralow density aerogel core synergistically restrains air circulation to limit convective heat transfer, while the poor conducting cellulose permitted little conductive heat transfer. The highly crystalline aerogel cellular walls prohibit infrared radiation, effectively suppressing heat transfer under extreme temperatures.