Graphene oxide thin films for flexible nonvolatile memory applications.

There has been strong demand for novel nonvolatile memory technology for low-cost, large-area, and low-power flexible electronics applications. Resistive memories based on metal oxide thin films have been extensively studied for application as next-generation nonvolatile memory devices. However, although the metal oxide based resistive memories have several advantages, such as good scalability, low-power consumption, and fast switching speed, their application to large-area flexible substrates has been limited due to their material characteristics and necessity of a high-temperature fabrication process. As a promising nonvolatile memory technology for large-area flexible applications, we present a graphene oxide based memory that can be easily fabricated using a room temperature spin-casting method on flexible substrates and has reliable memory performance in terms of retention and endurance. The microscopic origin of the bipolar resistive switching behavior was elucidated and is attributed to rupture and formation of conducting filaments at the top amorphous interface layer formed between the graphene oxide film and the top Al metal electrode, via high-resolution transmission electron microscopy and in situ X-ray photoemission spectroscopy. This work provides an important step for developing understanding of the fundamental physics of bipolar resistive switching in graphene oxide films, for the application to future flexible electronics.

Surface-patterned SU-8 cantilever arrays for preliminary screening of cardiac toxicity.

Arrays of a µgrooved SU-8 cantilever were utilized to analyze changes in the contraction force and beating frequency of cardiomyocytes in vitro. The longitudinally patterned µgrooves facilitates alignment of cardiomyocytes on top of the SU-8 cantilever, which increases the contraction force of cardiomyocytes by a factor of about 2.5. The bending displacement of the SU-8 cantilever was precisely measured in nanoscale using a laser-based measurement system combined with a motorized xyz stage. The cantilever displacement due to contraction of the cardiomyocytes showed the maximum on day 8 after their cultivation. Following preliminary experiments, Isoproterenol, Verapamil, and Astemizole were used to investigate the effect of drug toxicity on the physiology of cardiomyocytes. The experimental results indicated that 1 µM of Isoproterenol treatment increased contraction force and beating frequencies of cardiomyocytes by 30% and 200%, respectively, whereas 500 nM of Verapamil treatment decreased contraction force and beating frequencies of cardiomyocytes by 56% and 42%, respectively. A concentration of less than 5 nM of the hERG channel suppression drug Astemizole did not change the contraction forces in the displacement but slightly decreased the beating frequencies. However, irregular or abnormal heartbeats were observed at Astemizole concentrations of 5 nM and higher. We experimentally conformed that the proposed SU-8 cantilever arrays combined with the laser-based measurement systems has the great potential for a high-throughput drug toxicity screening system in future.

Penetration of the oral mucosa by parasite-like sperm bags of squid: a case report in a Korean woman.

We report a case of oral stings by spermatophores of the squid Todarodes pacificus . A 63-yr-old Korean woman experienced severe pain in her oral cavity immediately after eating a portion of parboiled squid along with its internal organs. She did not swallow the portion, but spat it out immediately. She complained of a pricking and foreign-body sensation in the oral cavity. Twelve small, white spindle-shaped, bug-like organisms stuck in the mucous membrane of the tongue, cheek, and gingiva were completely removed, along with the affected mucosa. On the basis of their morphology and the presence of the sperm bag, the foreign bodies were identified as squid spermatophores.