Miniaturized biomechanosensors for cardiomechanical studies

Mechanical force has provided invaluable information in the study of cardiomechanics. The force abnormality of single cardiac myocytes often reflects various levels of heart diseases because the contractile performance of the heart pump heavily depends on the cellular forces. The local and precise detection of cellular force is therefore expected to assist in the study of various conditions. In the present work, the design, fabrication and testing of miniaturized biomechanosensors are demonstrated using MEMS technologies. These biomechanosensors have been used to study living cells and demonstrated the ability to measure cellular forces with subcellular spatial resolution.;The cantilever-like structures demonstrate high sensitivities in the lateral plane. The probing ranging and sensitivity of these structures are analyzed using beam theories, and typical limitations in design and fabrication are identified. In order to build microscale polymer biomechanosensors, two types of polymer fabrication technologies are developed: (1) pressure-assisted micromolding and (2) pressure-assisted micropatterning. The first enables fabrication of polymer structures with various aspect ratios from a single master template; while the latter enables patterning of non-photodefinable polymer on top of rigid templates. The cellular force measurement is conducted in isolated cardiac myocytes and demonstrates a subcellular resolution. Moreover, simultaneous cell alignment in vitro and cellular force measurement are performed in cultured cardiac myocytes. The results conform to previous reports and validate the polymer structures as a viable tool for the study of cardiomechanics.;The nanoscale biomechanosensors are also presented for better probing resolution and enhanced spatial resolution. The polymer nanostructures are fabricated using E-beam nanolithography and replica molding. Since direct optical microscopy is no longer appropriate at nanoscale, scanning moire technology is used. The deformation of the polymer nanostructures is induced by thermal expansion and measured using scanning moire technology, validating the utilities of the nanoscale biosensors.;This work also includes development of silicon nanostructures with flexible profiles and metal-capped polymer microstructures. These structures add to the above ones to provide a full set of functional biomechanosensors at small scale.