Graphene-Based Thermopneumatic Generator for On-Board Pressure Supply of Soft Robots.

Various fields, including medical and human interaction robots, gain advantages from the development of bioinspired soft actuators. Many recently developed grippers are pneumatics that require external pressure supply systems, thereby limiting the autonomy of these robots. This necessitates the development of scalable and efficient on-board pressure generation systems. While conventional air compression systems are hard to miniaturize, thermopneumatic systems that joule heat a transducer material to generate pressure present a promising alternative. However, the transducer materials of previously reported thermopneumatic systems demonstrate high heat capacities and limited surface area resulting in long response times and low operation frequencies. This study presents a thermopneumatic pressure generator using aerographene, a highly porous (>99.99%) network of interconnected graphene microtubes, as lightweight and low heat capacity transducer material. An aerographene pressurizer module (AGPM) can pressurize a reservoir of 4.2 cm3 to ∼14 kPa in 50 ms. Periodic operation of the AGPM for 10 s at 0.66 Hz can further increase the pressure in the reservoir to ∼36 kPa. It is demonstrated that multiple AGPMs can be operated parallelly or in series for improved performance. For example, three parallelly operated AGPMs can generate pressure pulses of ∼21.5 kPa. Connecting AGPMs in series increase the maximum pressure achievable by the system. It is shown that three AGPMs working in series can pressurize the reservoir to ∼200 kPa in about 2.5 min. The AGPM's minimalistic design can be easily adapted to circuit boards, making the concept a promising fit for the on-board pressure supply of soft robots.

Multifunctional Three-in-One Sensor on t-ZnO for Ultraviolet and VOC Sensing for Bioengineering Applications.

Zinc oxide (ZnO) is considered to be one of the most explored and reliable sensing materials for UV detection due to its excellent properties, like a wide band gap and high exciton energy. Our current study on a photodetector based on tetrapodal ZnO (t-ZnO) reported an extremely high UV response of ~9200 for 394 nm UV illumination at 25 °C. The t-ZnO network structure and morphology were investigated using XRD and SEM. The sensor showed a UV/visible ratio of ~12 at 25 °C for 394 nm UV illumination and 443 nm visible illumination. By increasing the temperature, monotonic decreases in response and recovery time were observed. By increasing the bias voltage, the response time was found to decrease while the recovery time was increased. The maximum responsivity shifted to higher wavelengths from 394 nm to 400 nm by increasing the operating temperature from 25 °C to 100 °C. The t-ZnO networks exhibited gas-sensing performances at temperatures above 250 °C, and a maximum response of ~1.35 was recorded at 350 °C with a good repeatability and fast recovery in 16 s for 100 ppm of n-butanol vapor. This study demonstrated that t-ZnO networks are good biosensors that can be used for diverse biomedical applications like the sensing of VOCs (volatile organic compounds) and ultraviolet detection under a wide range of temperatures, and may find new possibilities in biosensing applications.

Gold standard medical therapy for glaucoma: defining the criteria identifying measures for an evidence-based analysis.

BACKGROUND: Over the past decade, several new medical therapies have become available for the treatment of primary open-angle glaucoma (POAG). A systematic evidence-based approach for identifying an optimal therapeutic agent is lacking. OBJECTIVES: The aims of this review were to critically evaluate published treatment recommendations for POAG and, based on a systematic review of the literature, to develop criteria that would define a "gold standard" medical therapy that reflects new treatment advances and established therapeutic goals. METHODS: A MEDLINE search spanning the years 1966 to 2002 and using the search terms gold standard, drug of choice, agent of choice, benchmark, ophthalmology, eye, and glaucoma was conducted and the results reviewed by a panel of 15 experts in the field of glaucoma. Published treatment recommendations for POAG were discussed. Criteria, anchored to medical evidence, for distinguishing a standard of medical therapy for POAG were defined. RESULTS: The terms connoting a gold standard therapy were found in only 258 of approximately 368,000 ophthalmology-related citations and 53 of almost 23,000 glaucoma citations, validating the need to define therapeutic standards. The lack of recommendations for the use of new classes of ocular hypotensive agents was acknowledged. Criteria identified to evaluate intraocular pressure (IOP)-lowering agents as gold standards included the following: efficacy in reducing IOP consistently over a 24-hour period to a level that will preserve the visual field and protect the optic nerve without inducing tachyphylaxis and tolerance, paucity of local and systemic adverse effects, promotion of patient compliance, and applicability in diverse patient populations. CONCLUSIONS: These criteria should be employed as measures for evidence-based analyses to evaluate available and future IOP-lowering medical therapies for POAG. The conceptual framework presented may be applicable to other therapeutic areas.