Chien-Chung Fu

Multidrug release based on microneedle arrays filled with pH-responsive PLGA hollow microspheres.

This work presents an approach to codelivering transdermally two model drugs, Alexa 488 and Cy5, in sequence, based on a system of polyvinylpyrrolidone microneedles (PVP MNs) that contain pH-responsive poly(d,l-lactic-co-glycolic acid) hollow microspheres (PLGA HMs). The MN system provides the green fluorescence of Alexa 488 in PVP MNs, the red fluorescence of the DiI-labeled PLGA shell of HMs, and the cyan fluorescence of Cy5 in their aqueous core. Combined together, the prepared MN arrays support the localization of the HMs and the monitoring of the release profiles of model drugs within the skin tissues. The key component of this system is NaHCO(3), which can be easily incorporated into HMs. After HMs are treated with an acidic solution (simulating the skin pH environment), protons (H(+)) can rapidly diffuse through the free volume in the PLGA shells to react with NaHCO(3) and form a large number of CO(2) bubbles. This effect generates pressure inside the HMs and creates pores inside their PLGA shells, releasing the encapsulated Cy5. Test MNs were strong enough to be inserted into rat skin without breaking. The PVP MNs were significantly dissolved within minutes, and the first model drug Alexa 488, together with HMs, were successfully deposited into the tissues. Once in the acidic environment of the skin, the released HMs started to release Cy5 and continued to spread throughout the neighboring tissues, in a second step of the release of the drug. This approach can be used clinically to codeliver sequentially and transcutaneously a broad range of drugs.

Different fabrication methods of out-of-plane polymer hollow needle arrays and their variations

We demonstrate, in this paper, different methods for the fabrication of various out-of-plane hollow micro needle arrays through back side exposure. We validated the back side exposure to be capable of producing microstructures with taper angles experimentally. Then we found that the taper angles can be adjusted by changing the distance between the photo mask absorber and the photoresist. Solid micro needles can be fabricated by properly calculating the side wall tilting angle and the thickness of the photo resist, while hollow micro needles can be realized by one lithography step through appropriate combination of different back side exposure methods. In this paper, we also demonstrate the capability of fabricating a micro needle array on a flexible membrane for further medical applications.

Magnetically driven micro ball valves fabricated by multilayer adhesive film bonding

A new manufacturing method has been used to produce a magnetically driven micro ball valve. The micro ball valve consists of three hot-embossed polymer layers and three metal layers. The layers are bonded with adhesive films which are microstructured by a punching process. The valve uses iron balls with a diameter of 3 mm as moving parts driven by a commercially available coil. The valve switches up to 200 kPa differential pressure with an initial current of 300 mA. The on–off switch frequency investigated was up to 30 Hz. In addition, the valve can operate as a proportional valve regulating the outlet pressure range from 0 to 112.5 kPa at an input pressure of 200 kPa. A switching time of 10 ms was measured.

3D high aspect ratio micro structures fabricated by one step UV lithography

We are going to present in this paper an interesting idea to fabricate 3D high aspect ratio micro structures. Pillars with different heights can be generated with one step UV lithography. Various 3D micro structures have been successfully fabricated. We will introduce the idea of this approach, fabrication details, and plenty of successful experimental results in this paper. A Taiwan 3D terrain map will be selected to demonstrate the ability of the proposed method.

Leptospiral Outer Membrane Lipoprotein LipL32 Binding on Toll-like Receptor 2 of Renal Cells As Determined with an Atomic Force Microscope

Leptopirosis is a renal disease caused by pathogenic Leptospira that primarily infects the renal proximal tubules, consequently resulting in severe tubular injuries and malfunctions. The protein extracted from the outer membrane of this pathogenic strain contains a major component of a 32 kDa lipoprotein (LipL32), which is absent in the counter membrane of nonpathogenic strains and has been identified as a crucial factor for host cell infection. Previous studies showed that LipL32 induced inflammatory responses and interacted with the extracellular matrix (ECM) of the host cell. However, the exact relationship between LipL32-mediated inflammatory responses and ECM binding is still unknown. In this study, an atomic force microscope with its tip modified by purified LipL32 was used to assess the interaction between LipL32 and cell surface receptors. Furthermore, an antibody neutralization technique was employed to identify Toll-like receptor 2 (TLR2) but not TLR4 as the major target of LipL32 attack. The interaction force between LipL32 and TLR2 was measured as approximately 59.5 +/- 8.7 pN, concurring with the theoretical value for a single-pair molecular interaction. Moreover, transformation of a TLR deficient cell line with human TLR2 brought the interaction force from the basal level to approximately 60.4 +/- 11.5 pN, confirming unambiguously TLR2 as counter receptor for LipL32. The stimulation of CXCL8/IL-8 expression by full-length LipL32 as compared to that without the N-terminal signal peptide domain suggests a significant role of the signal peptide of the protein in the inflammatory responses. This study provides direct evidence that LipL32 binds to TLR2, but not TLR4, on the cell surface, and a possible mechanism for the virulence of leptospirosis is accordingly proposed.

Optogenetic control of selective neural activity in multiple freely moving Drosophila adults

Significance We present an automated laser tracking and optogenetic manipulation system (ALTOMS) for studying social memory in Drosophila. Based on behavioral interactions computed with a high-speed image analysis system, ALTOMS can target two lasers (a 473-nm blue laser and a 593.5-nm yellow laser) independently on any specified body parts of two freely moving Drosophila adults in real time. We performed an operant conditioning assay in which a courting male quickly learned and formed a long-lasting memory to stay away from a freely moving virgin female. Given its capacity for optogenetic manipulation to transiently and independently activate/inactivate selective neurons, ALTOMS offers opportunities to systematically map brain circuits that orchestrate specific Drosophila behaviors. We present an automated laser tracking and optogenetic manipulation system (ALTOMS) for studying social memory in fruit flies (Drosophila melanogaster). ALTOMS comprises an intelligent central control module for high-speed fly behavior analysis and feedback laser scanning (∼40 frames per second) for targeting two lasers (a 473-nm blue laser and a 593.5-nm yellow laser) independently on any specified body parts of two freely moving Drosophila adults. By using ALTOMS to monitor and compute the locations, orientations, wing postures, and relative distance between two flies in real time and using high-intensity laser irradiation as an aversive stimulus, this laser tracking system can be used for an operant conditioning assay in which a courting male quickly learns and forms a long-lasting memory to stay away from a freely moving virgin female. With the equipped lasers, channelrhodopsin-2 and/or halorhodopsin expressed in selected neurons can be triggered on the basis of interactive behaviors between two flies. Given its capacity for optogenetic manipulation to transiently and independently activate/inactivate selective neurons, ALTOMS offers opportunities to systematically map brain circuits that orchestrate specific Drosophila behaviors.

Improvement of viscoelastic effects of dielectric elastomer actuator and its application for valve devices

In this paper we investigated the actuation behavior of the antagonistically driven Dielectric Elastomer Actuators (DEAs). The motivation is to improve the viscoelastic creeping behavior that intrinsically exists within most DEAs, since creeping behavior may cause some unwanted effects to the performance of DEAs, especially when we apply the DEAs to some mechanical devices which need to operate stably for a long time. Our experimental results showed that the actuator can generate very stable displacement, make the pattern of actuators movement more regular and take advantage of mechanical energy in a more efficient way by coating two dielectric elastomers with different area ratios and applying DC voltage to both of them at the same time.

A novel and simple fabrication method of embedded SU-8 micro channels by direct UV lithography

In this paper, we presents a novel and simple method to fabricate embedded micro channels. The method based on different light absorption properties of the SU-8 thick photoresist under different incident UV wavelengths. The channel structures are defined by the ordinary I-line, while the cover layer is patterned by the deep UV. Because the deep UV is obtained directly on the same aligner with a set of filter mirrors, the embedded channel can be easily produced without other rare facilities. Besides, the relationship between the thickness of the top layer and the exposure dose of the deep UV has been measured by an ingeniously designed experiment. The specific thickness of the top layer of the embedded micro channel can then be secured by the specific deep-UV exposure dose. Further more, many meaningful mechanical structures have been realized by this method, the material property of the top layer are also measured.

Effects of Impact Inertia and Surface Characteristics on Deposited Polymer Droplets in Microcavities

Microflow visualization and computational fluid dynamics (CFD) are complementarity performed to study the evolution of a single poly(ethylenedioxythiophene) (PEDOT) droplet ejected from a piezoelectric ink-jet printhead and the equilibrium film characteristic of the droplet deposition in a microfabricated cavity. The verified CFD code is further applied to investigate the influences of contact angles thetass of the PEDOT droplet/air interface and the PEDOT droplet/cavity sidewall interface as well as droplet impact velocity Vd on the transient deposition process in the micro cavity. Impact inertia was studied by varying the droplet Weber number from 30.3 to 42.6. The surface characteristics are explored by choosing thetass of 10deg, 30deg, 50deg, 70deg, 90deg, and 110deg. The influences of impact inertia are also examined by increasing Vd from 2.0 to 12.0 m/s at 2.0 m/s interval. The computed results are found in good agreement with the experimental ones. For the first time, critical Weber numbers have been found relating to the ability of the droplet to wet the side walls and fill a microcavity with a uniform film. The results are also new in terms of the identifications of the critical contact angle (thetass)C and critical impact velocity (Vd)c. At (thetass)C and at and beyond (Vd)c, the formation of an intact flat film in the cavity is fulfilled.

The proximity between C-termini of dimeric vacuolar H+-pyrophosphatase determined using atomic force microscopy and a gold nanoparticle technique

Vacuolar H+‐translocating inorganic pyrophosphatase [vacuolar H+‐pyrophosphatase (V‐PPase); EC 3.6.1.1] is a homodimeric proton translocase; it plays a pivotal role in electrogenic translocation of protons from the cytosol to the vacuolar lumen, at the expense of PPi hydrolysis, for the storage of ions, sugars, and other metabolites. Dimerization of V‐PPase is necessary for full proton translocation function, although the structural details of V‐PPase within the vacuolar membrane remain uncertain. The C‐terminus presumably plays a crucial role in sustaining enzymatic and proton‐translocating reactions. We used atomic force microscopy to visualize V‐PPases embedded in an artificial lipid bilayer under physiological conditions. V‐PPases were randomly distributed in reconstituted lipid bilayers; approximately 43.3% of the V‐PPase protrusions faced the cytosol, and 56.7% faced the vacuolar lumen. The mean height and width of the cytosolic V‐PPase protrusions were 2.8 ± 0.3 nm and 26.3 ± 4.7 nm, whereas those of the luminal protrusions were 1.2 ± 0.1 nm and 21.7 ± 3.6 nm, respectively. Moreover, both C‐termini of dimeric subunits of V‐PPase are on the same side of the membrane, and they are close to each other, as visualized with antibody and gold nanoparticles against 6×His tags on C‐terminal ends of the enzyme. The distance between the V‐PPase C‐terminal ends was determined to be approximately 2.2 ± 1.4 nm. Thus, our study is the first to provide structural details of a membrane‐bound V‐PPase dimer, revealing its adjacent C‐termini.