Nanocomposites membrane technology

In the recent years, we have been actively engaged in research topics involving clean water, sensor technology, alternative energy and biomedical devices.

A wide range of nanoparticles designed for remediation activities, the development of biosensors for chemicals and biological agents, the development of environmental filtration systems, green energy, and green manufacturing are being investigated. There are several target areas of concern when discussing environment. Water, air, soils, energy, weathering, human health are some of the frequently addressed areas. Although scientists and researchers have worked hard to decrease the dependence on highly toxic fossil fuels, there is minimum success in reducing the environmental impact. Nanotechnology is a viable solution for this long-lasting battle.

Nanocomposites (combining nanoparticles and a binding agent, often polymer resins) offer many useful properties for environmental remediation such as high surface area, enhanced interfacial reactivity, easy dispersibility, and facile sorption kinetics. The current research directions such as gas separation, molecular identification, water filtration, and biosensing applications are undertaken. For instance, polymer membranes have shown great salt rejection ability in literatures, however, the water flux performance is inherently poor. As a result, additives are added in an attempt to increase water flux.

Polyethylene Glycol (PEG) and graphene nano-platelet are chosen as the additive due to different degrees of hydrophobicity. Polysulfone (PSF) and polydimethylsiloxane (PDMS) are inherently hydrophilic; by manipulating the hydrophilic and hydrophobic characteristics of nanoparticle and polymer matrix an increase of water flux in membrane is expected.

Prosthetics development

Artificial limbs. According to Physical Medicine and Rehabilitation 2008 (Estimating the Prevalence of Limb Loss in the United States: 2005 to 2050), there are approximately 2 million amputees in the United States nowadays. Among those people, about half of the amputations are resulted from nerve damage and poor blood circulation due to diabetes and the remaining half are resulted from accidents. Due to their lightweight and high strength properties, carbon fiber composites are one of the most popular materials used for those who need artificial limbs. Aside from the lightweight property making it one of the top used prosthetic materials, it also allows the prosthetics to be easily tailored into desired configurations with high durability.

However, the high strength material often demonstrates unyielding stiffness and brittleness. These characteristics have resulted a significant discomfort for patients during walking, running, or bicycling. Many factors must be considered in creating, designing, and manufacturing the prosthetic parts. These include the material properties, geometries, bio-compatibility, etc. The rigidity of carbon fiber makes it less suitable for patients that are athletic.

There have been noticeable cracks that occurred in the most stress concentrated areas in their prosthesis. Therefore, a possible solution to resolve this issue is to reinforce the matrix with a different type of fiber, such as glass fiber, bamboo fiber, or Kevlar fiber. A hybrid material, such as carbon fiber interwoven with Kevlar fiber can be a desirable alternative.

With different demands and requirements for each patient, it is a crucial challenge to meet their needs. Based on our recent research results, the tensile strength of the carbon fiber is about 20% higher than that of hybrid fiber composite. The ductility (percent of elongation) of the carbon fiber is 1% higher than that of hybrid fiber composite under tension. The flexural strength of the carbon fiber composite is about 10% greater than that of hybrid fiber composite. The flexural modulus of elasticity of the hybrid fiber is more than 50% lower than that of carbon fiber. With a 10-20% sacrifice in the tension and flexural strength, the flexibility is significantly improved in the hybrid configuration. This shall be consulted to the orthopedic practitioners to determine such modification is acceptable.

Recent Funding

1. Integrating Sustainability into Lower Division Core Engineering Courses
   National Science Foundation (NSF), 2009-2011.
   Co-PI, $150,000.
2. Nanoscale Materials and Device Characterization Program, Characterization of Variable Platform for Robust Sensor and Separation Nanocomposite Membranes.Defense Microelectronics Activity (DMEA), 2008-2011.Senior Personnel, $1,105,660.
3. Nanoscale Materials and Device Characterization Program, Characterization of Nanoporous Organosilicate Thin Films for Ultra Low Dielectric Constants. DMEA, 2006-2008. Senior Personnel, $914,000.