Effect of surfactant concentration on the evaporation-driven deposition of carbon nanotubes: from coffee-ring effect to strain sensing

Carbon nanotubes (CNTs) as electrically conductive materials are of great importance in the fabrication of flexible electronic devices and wearable sensors. In this regard, the evaporation-driven self-assembly of CNTs has attracted increasing attention. CNT-based applications are mostly concerned with the alignment of CNTs and the density of CNT films. In the present work, we focus on the latter by trying to achieve an optimal evaporation-driven deposition with the densest CNT ring. Although surfactants are used for effective dispersion and colloidal stabilization of CNTs in the aqueous phase, their excessive usage induces Marangoni eddies in the evaporating sessile droplets, leading to poor ring depositions. Thus, there is an optimum surfactant concentration that contributes to CNTs deagglomeration and results in the densest ring-like deposition with relatively high thickness. We report that this optimum concentration for sodium dodecyl sulfate (SDS) as a surfactant can be approximately considered as much as the concentration of multi-walled carbon nanotubes (MWCNTs) as the colloidal nanoparticles. Optimal depositions show the lowest electrical resistances for each CNT concentration, making them suitable for electronic applications. We also propose the multiple depositions method in which a new droplet is printed after the complete evaporation of the previous droplet. This method can lead to denser rings with a higher conductivity using lower concentrations of CNTs. Lastly, we fabricate strain sensors based on the optimal evaporation-driven deposition of CNTs which show higher gauge factors than the commercial strain gauges, corroborating the applicability of our method.

Our discovery reveals the existence of an optimum SDS/CNT concentration ratio to achieve the highest conductivity of ring deposition for strain sensing.     

Fatal outcome following multiple bee stings: A rare case

Anaphylactic shock is an unexpected, life‐threatening, and sometimes fatal occurrence that affects patients in 75% of instances without a prior history of allergies. The severity of the reaction can vary among individuals. We report a case who died suddenly after being stung by bees in various parts of his body.     

Parasellar and optic nerve lesions: the neurosurgeon's perspective

For neuroradiologic evaluation of parasellar lesions, a wide array of examinations may be utilized. CT and MRI are used in the assessment of these lesions to establish the diagnosis and to assist the neurosurgeon in defining the precise location. Careful neuroradiologic assessment and close cooperation between the neurosurgeon and the neuroradiologist have much bearing on the surgical planning and eventual outcome of the patient.     

BOOK REVIEW: Data Book on Mechanical Properties of Living Cells, Tissues and Organs, edited by H. Abe, K. Hayashi, and M. Sato

PAC98: 0130Kj, 8722-q, 8745Bp     

An Implantable Artificial Lung

Self-contained artificial lung prototypes were implanted in 8 dogs and a calf for periods up to eight days. Ventilation and perfusion of the artificial organ are provided by pressures available in the pleural cavity and the pulmonary artery through the use of a silicone rubber ventilating envelope and an efficient, low-pressure manifold system. The three units with the largest membrane area (0.208 to 0.832 sq. m. had flow rates of 65 to 240 ml. per minute and oxygen transfer rates of 1.4 to 13.0 cc. per minute with room air ventilation. Design characteristics and the problems with implantation and long-term function are discussed.     

Port site recurrence after laparoscopic cholecystectomy

BACKGROUND: Gallbladder cancer diagnosis is usually at a later stage. Only 1% of gallbladder cancers are discovered fortuitously at infra-clinic stage when histological exam of cholecystectomy specimen. Laparoscopic cholecystectomy was realised for gallbladder lithiasis or polyps. Port site metastasis after laparoscopy was reported. The aim of our study is to report our series of port site metastasis complicating gallbladder cancer discovered fortuitously after laparoscopic cholecystectomy. METHODS: From 1 January 1994 to 31 December 2004, 2562 laparoscopic cholecystectomy was carried out. Ten gallbladder cancers were diagnosed than the incidence was 0.39%. RESULTS: Gallbladder cancer diagnosis was carried out by histology in 8 cases, and when port site metastasis in two cases whereas histological exam of cholecystectomy specimen was negative. Recurrence of gallbladder cancer was in port site in 4 cases. The mean rate survival of patients with port site metastases was 19 months.     

Antibacterial effect of two mineral trioxide aggregate (MTA) preparations against Enterococcus faecalis and Streptococcus sanguis in vitro

The antibacterial effects of gray-colored MTA (GMTA) and white-colored MTA (WMTA) against Enterococcus faecalis and Streptococcus sanguis were assessed in vitro using the tube dilution test. Broth tubes were prepared and divided into experimental and control groups. Aliquots of each of the tested microorganisms were taken from a stock culture and added to each experimental and positive control group. All groups were incubated at 37 degrees C and evaluated for turbidity at 0, 1, 24, 48, and 72-hour time periods. A direct correlation was found between GMTA and WMTA concentrations and their antibacterial effect. Tubes containing GMTA in concentrations of 50, 25, and 12.5 mg/ml did not show E. faecalis growth at any of the time periods tested whereas tubes containing WMTA showed E. faecalis growth at all concentrations and time periods tested. Statistically significant differences were found between tubes containing GMTA in concentrations of 50, 25 and 12.5 mg/ml and tubes containing similar concentrations of WMTA (p < 0.001). Tubes containing GMTA in concentrations of 50, 25, 12.5, 6.25, and 3.12 mg/ml and tubes containing WMTA in concentrations of 50, 25, and 12.5 mg/ml did not show S. sanguis growth at any of the time periods tested. Statistically significant differences were found between tubes containing GMTA in concentrations 6.25 and 3.12 mg/ml and tubes containing similar concentrations of WMTA (p < 0.001). It appears that the susceptibility of E. faecalis and S. sanguis to MTA differed and that GMTA requires lower concentrations than WMTA to exert the same antibacterial effect against each of the microorganisms tested.