Creation of Curved Nanostructures Using Soft-Materials-Derived Lithography.

In this study, curved nanostructures, which are difficult to obtain, were created on an Si substrate through the bonding, swelling, and breaking processes of the polymer and silicone substrate. This method can be utilized to obtain convex nanostructures over large areas. The method is simpler than typical semiconductor processing with photolithography or compared to wet- or vacuum-based dry etching processes. The polymer bonding, swelling (or no swelling), and breaking processes that are performed in this process were theoretically analyzed through a numerical analysis of permeability and modeling. Through this process, we designed a convex nanostructure that can be produced experimentally in an accurate manner.

Thermally assisted nanotransfer printing with sub-20-nm resolution and 8-inch wafer scalability.

Nanotransfer printing (nTP) has attracted considerable attention due to its good pattern resolution, process simplicity, and cost-effectiveness. However, the development of a large-area nTP process has been hampered by critical reliability issues related to the uniform replication and regular transfer printing of functional nanomaterials. Here, we present a very practical thermally assisted nanotransfer printing (T-nTP) process that can easily produce well-ordered nanostructures on an 8-inch wafer via the use of a heat-rolling press system that provides both uniform pressure and heat. We also demonstrate various complex pattern geometries, such as wave, square, nut, zigzag, and elliptical nanostructures, on diverse substrates via T-nTP. Furthermore, we demonstrate how to obtain a high-density crossbar metal-insulator-metal memristive array using a combined method of T-nTP and directed self-assembly. We expect that the state-of-the-art T-nTP process presented here combined with other emerging patterning techniques will be especially useful for the large-area nanofabrication of various devices.

Enhanced bendability of nanostructured metal electrodes: effect of nanoholes and their arrangement.

Metallic thin films often exhibit poor mechanical robustness, which makes them unsuitable for use as electrodes in flexible and stretchable electronic devices. This prompted us to investigate the effect of creating a pattern of nanoholes in a metallic thin film to its mechanical and electrical properties. The adoption of nanonetwork structures is shown to confer significantly improved bendability to the films, with a change in electrical resistance of only 21% after 10 000 bending cycles, under a bending strain of 6.3%. In contrast to the planar silver (Ag) films in which large cracks are formed, structures that contain nanoholes act as barriers that block the growth of cracks; consequently, only short cracks are formed in these films and therefore changes in their resistance are much lower. In this paper, we suggest a novel model based on random grain boundaries to simulate the behavior of various nanopattern arrangements when the film is subjected to mechanical stress. Our modeling studies revealed that nanoholes secure the electrical current pathways by effectively blocking crack propagation, and that optimizing orientation, size, and coverage of these nanoholes can further improve the mechanical properties. Although diamond patterns exhibit superior characteristics to those of rectangular ones, their directional dependence is shown to be reduced by adopting randomly dispersed nanostructures. We additionally verified experimentally that an array of holes (rectangular, diamond-shaped, and randomly patterned) significantly affects crack propagation and resistance change.

High-resolution nanotransfer printing applicable to diverse surfaces via interface-targeted adhesion switching.

Nanotransfer printing technology offers outstanding simplicity and throughput in the fabrication of transistors, metamaterials, epidermal sensors and other emerging devices. Nevertheless, the development of a large-area sub-50 nm nanotransfer printing process has been hindered by fundamental reliability issues in the replication of high-resolution templates and in the release of generated nanostructures. Here we present a solvent-assisted nanotransfer printing technique based on high-fidelity replication of sub-20 nm patterns using a dual-functional bilayer polymer thin film. For uniform and fast release of nanostructures on diverse receiver surfaces, interface-specific adhesion control is realized by employing a polydimethylsiloxane gel pad as a solvent-emitting transfer medium, providing unusual printing capability even on biological surfaces such as human skin and fruit peels. Based on this principle, we also demonstrate reliable printing of high-density metallic nanostructures for non-destructive and rapid surface-enhanced Raman spectroscopy analyses and for hydrogen detection sensors with excellent responsiveness.

The correlation between the treatment efficacy and the sympathetic activity in men with lower urinary tract symptoms.

PURPOSE: In this study, we examined the difference in the treatment efficacy depending on the sympathetic activity in men with lower urinary tract symptoms (LUTS). METHODS: In the current single-center, retrospective study, we evaluated a total of 66 male patients aged 40-70 years of age, presenting with LUTS, whose International Prostate Symptom Score (IPSS) exceeded 8 points. They had a past 3-month history of taking alfuzosin XL, and their heart rate variability (HRV) was measured before and after the treatment. In addition, we also recruited 39 healthy volunteers who visited a health promotion center for a regular medical check-up. They were aged between 40 and 70 years and had an IPSS of <8 points. We divided the patients with LUTS into two groups: the groups A and B, based on a low frequency/high frequency (LF/HF) ratio of 1.7, which was the mean value of the LF/HF ratio in the healthy volunteers. After a 3-month treatment with alfuzosin XL, we compared treatment outcomes, based on the IPSS and peak urine flow rate, between the two groups. RESULTS: A 3-month treatment with alfuzosin XL, comprising the measurement of the HRV, was performed for the 23 patients of the group A (23/38) and 17 of the group B (17/28). After a 3-month treatment with alfuzosin XL, total IPSS and IPSS questionnaire 2 and 5 were significantly lower in the group A as compared with the group B. But this was not seen in the group B. Furthermore, there were no significant differences in other parameters, such as maximal flow rate and IPSS storage subscore, between the two groups. CONCLUSIONS: Our results indicate that the treatment efficacy was lower in patients with sympathetic hyperactivity as compared with those with sympathetic hypoactivity. Thus, our results will provide a basis for further studies to clarify causes of LUTS in a clinical setting.

Comparative analysis of radiologically measured size and true size of renal tumors.

PURPOSE: We evaluated the differences between radiologically measured size and pathologic size of renal tumors. MATERIALS AND METHODS: The data from 171 patients who underwent radical or partial nephrectomy for a renal tumor at Ajou University Hospital were reviewed. Radiologic tumor size, which was defined as the largest diameter on a computed tomographic scan, was compared with pathologic tumor size, which was defined as the largest diameter on gross pathologic examination. RESULTS: Mean radiologic size was significantly larger than mean pathologic size for all tumors (p=0.019). When stratified according to radiologic size range, mean radiologic size was significantly larger than mean pathologic size for tumors <4 cm (p=0.003), but there was no significant difference between the sizes for tumors 4-7 cm and >7 cm. When classified according to histologic subtype, mean radiologic size was significantly larger than mean pathologic size only in clear cell renal cell carcinomas (p=0.002). When classified according to tumor location, mean radiologic size was significantly larger than mean pathologic size in endophytic tumors (p=0.043) but not in exophytic tumors. When endophytic tumors were stratified according to radiologic size range, there was a significant difference between the mean radiologic and pathologic sizes for tumors <4 cm (p=0.001) but not for tumors 4-7 cm (p=0.073) and >7 cm (p=0.603). CONCLUSIONS: Our results suggest that in planning a nephron-sparing surgery for renal tumors, especially for endophytic tumors of less than 4 cm, the tumor size measured on a computed tomography scan should be readjusted to get a more precise estimate of the tumor size.

Hospitalization decreases serum prostate-specific antigen values compared with outpatient values in patients with benign prostatic diseases.

PURPOSE: To investigate whether hospitalization influences serum prostate-specific antigen (PSA) values. MATERIALS AND METHODS: Transrectal ultrasound-guided prostate biopsies were performed for detecting prostate cancer in 2,017 patients between February 2001 and April 2011 at Ajou University Hospital. Of those patients, 416 patients who were hospitalized for prostate biopsies, whose serum PSA values were measured at the outpatient department within 1 month of admission and also just after admission, and who had negative prostate biopsy results were included in the present study. We retrospectively reviewed the data of the 416 patients and compared the serum PSA values measured in the outpatient department with those measured during hospitalization. RESULTS: Among all 416 patients, the interval between the two PSA measurements was 22.2 days (range, 3 to 30 days) and the prostate size measured by transrectal ultrasonography was 53.63 mL (range, 12.8 to 197.9 mL). Among all patients, mean serum PSA levels measured during hospitalization were significantly lower than those measured in the outpatient department (6.69 ng/mL vs. 8.01 ng/mL, p<0.001). When stratified according to age, the presence or absence of chronic prostatitis in the biopsy pathology, serum PSA levels, and prostate size, the serum PSA levels measured during hospitalization were significantly lower than those measured in the outpatient department in all subgroups, except in cases aged 20 to 39 years and those with PSA <4 ng/mL, in whom no significant differences were shown. CONCLUSIONS: Hospitalization decreases serum PSA values compared with those measured on an outpatient basis in patients with benign prostatic diseases. Therefore, serum PSA values should be checked on an outpatient basis for serial monitoring.