ABSTRACT
Caiusa Surcouf (Diptera: Calliphoridae) is an Old World genus of blow flies, the larvae of which feed on egg masses in the foam nests of various species of rhacophorid tree frogs. Here, we provide the first records for India (West Bengal, Eastern India) of Caiusa coomani Séguy, 1948 and C. karrakerae Rognes, 2015, together with new information on the behaviour and morphology of their larvae. Active surface swimming to disperse from infested nests is documented in blow fly larvae for the first time, as is the presence of a large internal air sac presumably acting as a floating aid. Chiromantis simus (Annandale, 1915) (Anura: Rhacophoridae) egg masses are first recorded as a feeding substrate of Caiusa larvae.
ABSTRACT
Conventional droplet generation approaches in digital microfluidics show ~10% variation in droplet volumes and are restricted to creating only small volumes. In this work, we demonstrate a new approach for splitting sample volumes precisely by gradually ramping down voltage, in place of abruptly switching off electrodes. This allows us to eliminate hydrodynamic instabilities responsible for variations in droplet volume. A simple visual method was developed for measuring sample volumes created on-chip. Our results show that generating and measuring arbitrary sample volumes accurately, with < 1% variation, is possible in electrowetting devices. The approach can be easily extended to existing digital microfluidic systems, and can potentially improve performance of applications requiring precise sample metering, such as immunoassays or DNA amplification.
ABSTRACT
Lab-on-a-chip systems rely on several microfluidic paradigms. The first uses a fixed layout of continuous microfluidic channels. Such lab-on-a-chip systems are almost always application specific and far from a true "laboratory." The second involves electrowetting droplet movement (digital microfluidics), and allows two-dimensional computer control of fluidic transport and mixing. The merging of the two paradigms in the form of programmable electrowetting channels takes advantage of both the "continuous" functionality of rigid channels based on which a large number of applications have been developed to date and the "programmable" functionality of digital microfluidics that permits electrical control of on-chip functions. In this work, we demonstrate for the first time programmable formation of virtual microfluidic channels and their continuous operation with pressure driven flows using an electrowetting platform. Experimental, theoretical, and numerical analyses of virtual channel formation with biologically relevant electrolyte solutions and electrically-programmable reconfiguration are presented. We demonstrate that the "wall-less" virtual channels can be formed reliably and rapidly, with propagation rates of 3.5-3.8 mm s(-1). Pressure driven transport in these virtual channels at flow rates up to 100 µL min(-1) is achievable without distortion of the channel shape. We further demonstrate that these virtual channels can be switched on-demand between multiple inputs and outputs. Ultimately, we envision a platform that would provide rapid prototyping of microfluidic concepts and would be capable of a vast library of functions and benefitting applications from clinical diagnostics in resource-limited environments to rapid system prototyping to high throughput pharmaceutical applications.
