Characterization of a reversible thermally-actuated polymer-valve: A potential dynamic treatment for congenital diaphragmatic hernia.

BACKGROUND: Congenital diaphragmatic hernia (CDH) is a fetal defect comprising an incomplete diaphragm and the herniation of abdominal organs into the chest cavity that interfere with fetal pulmonary development. Though the most promising treatment for CDH is via interventional fetoscopic tracheal occlusion (TO) surgery in-utero, it has produced mixed results due to the static nature of the inserted occlusion. We hypothesize that a suitable noninvasively-actuatable, cyclic-release tracheal occlusion device can be developed to enable dynamic tracheal occlusion (dTO) implementation. OBJECTIVE: To conduct an in-vitro proof-of-concept investigation of the construction of thermo-responsive polymer valves designed for targeted activation within a physiologically realizable temperature range as a first step towards potential development of a noninvasively-actuatable implantable device to facilitate dynamic tracheal occlusion (dTO) therapy. METHODS: Six thermo-responsive polymer valves, with a critical solution temperature slightly higher than normal physiological body temperature of 37°C, were fabricated using a copolymer of n-isopropylacrylamide (NIPAM) and dimethylacrylamide (DMAA). Three of the valves underwent ethylene oxide (EtO) sterilization while the other three served as controls for EtO-processing compatibility testing. Thermal response actuation of the valves and their steady-state flow performances were evaluated using water and caprine amniotic fluid. RESULTS: All six valves consisting of 0.3-mole fraction of DMAA were tested for thermal actuation of caprine amniotic fluid flow at temperatures ranging from 30-44°C. They all exhibited initiation of valve actuation opening at ~40°C with full completion at ~44°C. The overall average coefficient of variation (CV) for the day-to-day flow performance of the valves tested was less than 12%. Based on a Student t-test, there was no significant difference in the operational characteristics for the EtO processed versus the non-EtO processed valves tested. CONCLUSIONS: We successfully fabricated and demonstrated physiological realizable temperature range operation of thermo-responsive polymer valves in-vitro and their suitability for standard EtO sterilization processing, a prerequisite for future in-vivo surgical implantation testing.

Large discrete resistance jump at grain boundary in copper nanowire.

Copper is the current interconnect metal of choice in integrated circuits. As interconnect dimensions decrease, the resistivity of copper increases dramatically because of electron scattering from surfaces, impurities, and grain boundaries (GBs) and threatens to stymie continued device scaling. Lacking direct measurements of individual scattering sources, understanding of the relative importance of these scattering mechanisms has largely relied on semiempirical modeling. Here we present the first ever attempt to measure and calculate individual GB resistances in copper nanowires with a one-to-one correspondence to the GB structure. Large resistance jumps are directly measured at the random GBs with a value far greater than at coincidence GBs and first-principles calculations. The high resistivity of the random GB appears to be intrinsic, arising from the scaling of electron mean free path with the size of the lattice relaxation region. The striking impact of random GB scattering adds vital information for understanding nanoscale conductors.

Biocompatible MEMS electrode array for determination of three-dimensional strain.

Sensor arrays for the measurement of the load condition of polyethylene spacers in the total knee arthroplasty (TKA) prosthesis have been developed. Arrays of capacitive sensors are used to determine the three-dimensional strain within the polyethylene prosthesis component. Data from these sensors can be used to give researchers better understanding of component motion, loading, and wear phenomena for a large range of activities. These sensors implemented on a large scale will give clinicians feedback for individual patient biomechanics without the requirement for patient exposure to X-ray radiation. Patients will benefit from smart prosthetic components which allow clinicians monitor biomechanics and loading by applying noninvasive remedies such as orthotics or physical therapy for patients exhibiting poor biomechanics before wear or component failure become issues. In this paper, we present research regarding the design of a biocompatible strain sensor and the fabrication of microelectrode arrays on biocompatible polymer materials.