Subramaniyan Ramasundaram

An All-Elastomeric Transparent and Stretchable Temperature Sensor for Body-Attachable Wearable Electronics.

A transparent stretchable (TS) gated sensor array with high optical transparency, conformality, and high stretchability of up to 70% is demonstrated. The TS-gated sensor array has high responsivity to temperature changes in objects and human skin. This unprecedented TS-gated sensor array, as well as the integrated platform of the TS-gated sensor with a transparent and stretchable strain sensor, show great potential for application to wearable skin electronics for recognition of human activity.

N,N,N-Trimethyl chitosan nanoparticles for controlled intranasal delivery of HBV surface antigen

Hepatitis B virus surface antigen (HBsAg) loaded N,N,N-trimethyl chitosan nanoparticles (N-TMC NPs) were formulated and studied for controlled intranasal delivery. The size and surface properties of the NPs can be tuned by modifying the concentration of N-TMC and found to be 66±13, 76±9 nm for 0.25 and 0.5 wt.% respectively. Loading of 380 and 760 μl of HBsAg yielded 143±33, 259±47 nm sized spherical N-TMC NPs with highest loading efficiency and capacity of 90-93%, and 96-97% respectively. In vitro drug release analysis ensured 93% cumulative release of HBsAg antigen over prolonged period (43 days). In vivo immunological study was performed using 6-8 weeks old female BALB mice and reveals adjuvants efficiency of NPs for antigen is highly stable and better than standard. Obtained results show that N-TMC NPs can be extensively used in controlled intra nasal delivery to treat various diseases including hepatitis B and allergic rhinitis.

Titanium dioxide nanofibers integrated stainless steel filter for photocatalytic degradation of pharmaceutical compounds

A photocatalytically active stainless steel filter (P-SSF) was prepared by integrating electrospun TiO2 nanofibers on SSF surface through a hot-press process where a poly(vinylidene fluoride) (PVDF) nanofibers interlayer acted as a binder. By quantifying the photocatalytic oxidation of cimetidine under ultraviolet radiation and assessing the stability of TiO2 nanofibers integrated on the P-SSF against sonication, the optimum thickness of the TiO2 and PVDF layer was found to be 29 and 42 μm, respectively. At 10L/m(2)h flux, 40-90% of cimetidine was oxidized when the thickness of TiO2 layer increased from 10 to 29 μm; however, no further increase of cimetidine oxidation was observed as its thickness increased to 84 μm, maybe due to limited light penetration. At flux conditions of 10, 20, and 50 L/m(2) h, the oxidation efficiencies for cimetidine were found to be 89, 64, and 47%, respectively. This was attributed to reduced contact time of cimetidine within the TiO2 layer. Further, the degradation efficacy of cimetidine was stably maintained for 72 h at a flux of 10 L/m(2) h and a trans-filter pressure of 0.1-0.2 kPa. Overall, our results showed that it can potentially be employed in the treatment of effluents containing organic micropollutants.

Preparation, characterization, and application of TiO2-patterned polyimide film as a photocatalyst for oxidation of organic contaminants

Photocatalytically active TiO2-patterned polyimide (PI) films (PI-TiO2) were fabricated using thermal transfer patterning (TTP). When subjected to hot pressing, the TiO2 nanoparticles electrosprayed on steel mesh templates were successfully transferred and formed checker plate patterns on PI film. FE-SEM studies confirmed that pressing at 350°C and 100MPa was optimum for obtaining patterns with uniform TiO2 coverage. When the quantity of TiO2 on the template increased, the amount of it immobilized on PI film also increased from 0.3245 to 1.2378mg per 25cm2. XPS studies confirmed the presence TiO2 on the patterns, and indicated the formation of carboxylic acid and amide groups on the PI surface during TTP. When tested under UVA irradiation, PI-TiO2 with 1.2378mg/25cm2 TiO2 loading exhibited the highest photocatalytic performance for methylene blue (10μM) degradation, with a rate constant of 0.0225min-1 and stable photocatalytic efficacy for 25 cycles of reuse. The PI-TiO2 was also successfully used to degrade amoxicillin, atrazine, and 4-chlorophenol. During photocatalysis, the toxicity of 4-chlorophenol against Vibrio fischeri and the antibiotic activity of amoxicillin against Escherichia coli were decreased. Overall, TTP was found to be a potentially scalable method for fabricating robust immobilized TiO2 photocatalyst.

Binder-free immobilization of TiO2 photocatalyst on steel mesh via electrospraying and hot-pressing and its application for organic micropollutant removal and disinfection

An immobilized photocatalyst was prepared by thermally treating TiO2-coated steel mesh (TiO2-IS) in a laboratory hot-press with no binder. TiO2 coating was performed by electrospraying a 1 mg/mL methanol dispersion of Evonik P25 powder. The thermal treatment conditions at 350 °C, 100 Mpa, and 1 h were found to be the optimum conditions. Scanning electron microscopic images displayed a robust and adherent TiO2 layer on steel mesh. X-ray photoelectron spectroscopy and elemental mapping studies confirmed that the Fe3O4 interface formed during thermal treatment strongly bound the TiO2 on steel mesh. The XRD patterns of TiO2-IS indicated the preservation of crystalline structure of Evonik P25 (anatase and rutile mixture) and the existence of iron oxide interface. Under UVA irradiation, 10 μM of methylene blue was completely decolorized within 40 min using an immobilized photocatalyst with 2.120 mg of TiO2 per 2.5 × 5.0 cm2 and showed stable efficacy in 25 consecutive photocatalytic runs. Furthermore, this sample degraded the organic micropollutants (e.g., pharmaceuticals) such as carbamazepine, ranitidine, acetaminophen, and trimethoprim at the rates of 0.041, 0.165, 0.089, and 0.079 min-1, respectively. Under UVA irradiation, it exhibited high photocatalytic disinfection activity for Escherichia coli and MS2 coliphage.

Sensors: An All-Elastomeric Transparent and Stretchable Temperature Sensor for Body-Attachable Wearable Electronics (Adv. Mater. 3/2016)

On page 502, N.-E. Lee and co-workers demonstrate an integrated platform of transparent and stretchable temperature and strain sensors that are attachable to the human body, in order to simultaneously monitor subtle changes in skin temperature and strain during human activity. The transparent and stretchable integrated sensor platform has a great potential in a variety of applications including biomedical monitoring, human-activity monitoring, and human-machine interfaces.