A new thermally conductive polyimide composite film has been developed. It is based on a dispersion of different particle sizes of boron nitride (BN) in a polyimide (PI) precursor, polyamic acid (PAA). Subsequently, thermal imidization of PAA at 350 degrees C produced the corresponding polyimide composites. 3-Mercaptopropionic acid was used as the surfactant to modify the BN surface for the dispersion of BN in the polymer. The PI/BN composites showed different thermal conductivities at different proportion of BN particle sizes and contents. The thermal conductivity of the PI/BN composite was up to 1.2 W/m-k, for a mixture containing 30 wt % of micro and nanosized BN fillers in the polyimide matrix. The PI/BN composites had excellent thermal properties. Their glass transition temperatures were above 360 degrees C, and thermal decomposition temperatures were over 536 degrees C.

A segmented rigid-rod polyimide has been synthesized from 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) and 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl (PFMB) in refluxing m-cresol. The polymer is soluble in hot phenolic solvents and can be solution cast into thin films. When the films are highly oriented, the polymer crystallizes in a monoclinic lattice with a = 15.40 A, 6 = 9.918 A, c * 20.21 A, and y = 56.2°. When unoriented films are annealed at 425 and 450 °C, an in-plane orientation process of the crystals and chain molecules takes place, so that the crystals' c axes end up parallel to the films' surfaces. This is followed by further structure development where the apparent crystal size increases with annealing time and temperature. It is postulated that the long-range molecular motion required for orientation is facilitated by residual solvent in the film. Avrami exponents for the structure development support a molecular-motioncontrolled process.

Rapid diagnosis and screening of diseases have become increasingly important in predictive and preventive medicine as they improve patient treatment strategies and reduce cost as well as burden on our healthcare system. In this regard, wearable devices are emerging as effective and reliable point-of-care diagnostics that can allow users to monitor their health at home. These wrist-worn, head-mounted, smart-textile, or smart-patches devices can offer valuable information on the conditions of patients as a non-invasive form of monitoring. However, they are significantly limited in monitoring physiological signals and biomechanics, and, mostly, rely on the physical attributes. Recently, developed wearable devices utilize body fluids, such as sweat, saliva, or skin interstitial fluid, and electrochemical interactions to allow continuous physiological condition and disease monitoring for users. Among them, tear fluid has been widely utilized in the investigation of ocular diseases, diabetes, and even cancers, because of its easy accessibility, lower complexity, and minimal invasiveness. By determining the concentration change of analytes within the tear fluid, it would be possible to identify disease progression and allow patient-oriented therapies. Considering the emerging trend of tear-based biosensing technology, this review article aims to focus on an overview of the tear fluid as a detection medium for certain diseases, such as ocular disorders, diabetes, and cancer. In addition, the rise and application of minimally invasive detection and monitoring via integrated contact lens biosensors will also be addressed, in regards to their practicality and current developmental progress.

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