Research Topics

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• NANO/BIO MECHANICS

  MOLECULAR MOTORS

  POLYMER NANOCOMPOSITES

  BACKGROUND INFORMATION

• NANO/BIO MECHANICS

  Mechanical forces—like biochemical signals—play a vital role in regulating fundamental cellular processes. Fibroblasts—critical for wound healing and tissue construction—proliferate and migrate, powered by their own internal contractile forces. Tumor cells are strong enough to rip-open cell-cell junctions, enabling proliferation, scattering and metastasis due to their oncogenically strengthened contractile elements. Stem cells commit to different lineages as regulated by forces and compliances in their local microenvironments. Growing tissue relies on mechanical forces to help it produce a vascular system vital for supplying nutrients, but excessive intracellular forces suppress vascularization leading to necrosis. Characterizing—towards the ultimate goal of controlling—mechanical forces and dynamics inside non-muscle cells is central to future advances in medicine and bioengineering.

  The actin–activated motor protein, myosin—perhaps best known for its prime role in muscle contraction—plays a principal role in generating these intracellular mechanical forces. Until the late 1960’s, scientists believed that actin filaments and myosin existed only in muscle cells, where they were titin-bound into stable, sarcomeric ultrastructures responsible for muscle contraction.5 That was until a startling discovery was made: non-muscle cells also contain actin filaments and myosin—albeit assembled into labile non-sarcomeric substructures. Within a decade, actin and myosin isoforms had been found in virtually every eukaryotic cell with one particular isoform—myosin II—responsible for contractile motion and force generation. Today, nearly three decades of research later, actomyosin (actin-myosin II) contractility is recognized to be as vital to the functioning of non-muscle cells as it is to muscle cells.

• MOLECULAR MOTORS

Responsible for the proper functioning of virtually every living cell, molecular motors are nanoscale, self-assembled, ultra-efficient, biological machines. These “nanomotors” convert chemical energy—from hydrolysis of ATP (adenosine triphosphate) or acceptance of protons—into mechanical work, powering vital cellular processes. For example, nature’s most powerful and efficient nanomotor is a proton-fueled rotary motor that propel bacteria; it delivers ~20pN pushing a bacterium ~1mm/s, producing ~13.6kW/kg—about 45 times that of modern gasoline engines. Not surprisingly biological nanomotors have captured the imagination of nanotechnologists intent on exploiting their power density and stroke length to synthesize (or selectively pattern) hierarchical, nano-featured materials. Nevertheless their salient roles remain within living organisms producing motion and performing mechanical work.

Motor proteins—a principal class of molecular motors powered by ATP hydrolysis—drive intracellular movement and transport. The most prominent subclass myosin—best known as the prime mover in muscle contraction—is actually a diverse, superfamily of actin-activated motor proteins found in all eukaryotic cells that produce essential intracellular tractions and motion. In the ubiquitous non-muscle cells, myosin powers a labile actin cytoskeleton—an intracellular scaffold of actin filaments (F-actin) and accessory proteins that controls and mediates many primal cellular functions, e.g. motility, differentiation, division, cytokinesis, adhesion, signaling and transport.

• POLYMER NANOCOMPOSITES
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• Nano-modification strategies provide a viable means to create lightweight, comfortable and flame resistant fabrics for military and civilian personnel. To increase escape time and reduce burn injuries from survivable incidents, the Army and Marine Corps desire low–cost flame and thermal protection for individual infantry soldiers to mitigate against a variety of fire hazards, including those that occur in combat (rural and urban warfare), operations other than war, and standard operational duty. Current infantry uniforms are not flame resistant, nor do they self-extinguish flames. A lightweight, comfortable, durable clothing ensemble with flame resistant properties is desired. The integration of durable, nano-scale clays and flame resistant additives to nylon and/or cotton fibers may offer the opportunity to retain the desirable characteristics of a nylon/cotton blend fabric while significantly enhancing its flame protection (as measured by safe exposure times) yet adding negligible additional weight. Equally important, unlike a coating or finish that can be worn or washed away, the nano-modification is permanent as it is perfuse throughout the fabric fibers/yarns. This technology would apply to every person required to wear flame resistant garments; end-users range from Special Operations Forces, dismounted infantry soldier, aircraft carrier deck personnel, Space Shuttle crew, fire fighters, and other Homeland Defense (HD) personnel including police, firefighters and other first responders. In the civilian sector, applications include: refinery and plant operation, steel and metal smelting industry, power supply industry, civilian aircraft seating/upholstery, flame retardant bedding, motor racing suits and pit crew outfits, automotive heat shields, etc.