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This paper illustrates a new method for creating air separated droplets on demand at a microfluidic T-junction in a microchannel using electrowetting-on-dielectric (EWOD). This new mechanism enables digital control of droplet formation that is not achievable by conventional continuous flow T-junction systems. The developed system can be used for dispensing droplets for biomedical applications including...
This work investigates the effect of selected linear image processing methods on the depth of correlation (DoC) in micro particle image velocimetry using a single camera. In practice, band-pass and high-pass filters (background subtraction) are commonly applied to micro particle image velocimetry images. This work provides analytical models describing the effect of the parameters of low-, high-, and...
We have developed an all-polymer, micro-inkjet printed, flexural plate wave (FPW) sensor for toluene vapor detection. The sensor consists of a piezoelectric polyvinylidene fluoride (PVDF) substrate with conductive polyethylenedioxythiophene polystyrene sulfonate (PEDOT:PSS) interdigitated transducers (IDTs) and a polymer sensing layer coating for selective absorption of a targeted analyte. Sensor...
Transdermal drug delivery can potentially replace hypodermic needles for injection of many compounds. The batch production of metallic microneedle arrays has been restricted by the time-consuming steps associated with previous fabrication processes. Here, we are presenting a process that allows rapid production of microneedle arrays with any number of needles as well as any desired needle dimensions...
We have developed an inexpensive inkjet printing process to fabricate percolation-based resistive strain gauges in a paper substrate. These strain sensors were fabricated by inkjet printing different suspensions containing conductive carbon black (CB). We have measured the resistance of these elements as a function of strain under low frequency cyclic loads to characterize the sensitivity of these...
We demonstrate an all-polymer flexural-plate-wave gravimetric sensor using piezoelectric PVDF and conductive PEDOT:PSS. An inkjet-printed interdigital transducer (IDT) is used to excite Lamb waves within the film that are measured both electronically, using a second IDT, and mapped directly using a scanning laser Doppler vibrometer. Pulsed wave excitation isolates the weak acoustic signal from the...
Microneedles are tiny hollow structures that allow painless drug delivery into human skin. In this work, we present a novel fabrication method for microstructures based on solvent casting that allows rapid fabrication of inexpensive microneedles from polymer materials. The polymer microneedles are formed on a reusable mold made with a single photolithography step. The strength of the fabricated microneedles...
This work demonstrates a new 2-stage valving concept for microfluidic systems based on polydimethylsiloxane (PDMS) that uses the reversible gelation of a thermally responsive polymer solution in a control channel to deflect a membrane into the main flow channel for flow control. This method can control flow through a system of PDMS channels using integrated electric heating elements and only one control...
In this paper, we report the development of a multi-turn gradient coil assembly suitable for microscale static and flow imaging using magnetic resonance imaging (MRI) techniques. A novel microfabrication technique to manufacture the gradient coils is presented. The triaxial gradient assembly has gradient sensitivities exceeding 0.044 T/(mmiddotA) over a spherical region with a diameter of 4 mm. A...
Polymer microspheres are commonly used in microfluidic devices for biomedical applications. However, the presence of these particles can compromise the reliable operation of the microfluidic devices, as particles have been observed to deposit successively until they block a flow passage, which then leads to device failure. This paper presents investigations of the mechanics of particle deposition...
We demonstrate a new design for micromirror arrays that allow for high tilt angles (0.75deg) of mirror elements in arbitrary directions, large actuated areas (0.64 mm2), and high actuation bandwidth (measured resonant frequencies range from 100 to 450 kHz). This is achieved by subdividing each actuated mirror into several small submirrors that are addressed simultaneously, so that they behave as one...
Two new neurolenin-type sesquiterpene lactones were found in the leaves of Neurolaena macrocephala Sch. Bip. Ex Hemsl. (Asteraceae). These compounds were identified by their NMR spectra as the 8β-isobutyryloxy- and 8β- (2-methyl)butyryloxy analogs of neurolenin B. Additionally, the known neurolenins B, C and D and the furanoheliangolide 9a-acetoxy-8β-isovaleryloxy-calyculatolide were found to be present...
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