Modular microfluidic valve structures based on reversible thermoresponsive ionogel actuators

Benito‐Lopez, Fernando; Antoñana-Díez, Marta; Curto, Vincenzo F.; Diamond, Dermot; Castro-López, Vanessa

doi:10.1039/c4lc00568f

Cited by 57 publications

(50 citation statements)

References 30 publications

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“…The alginate/PNIPAAm ICE gels show promise for application as actuators because they can repetitively achieve a large free strain and blocked stress. We demonstrated how these materials can be fabricated into a smart valve for control of water flow with 4D printing. A multicomponent computer‐aided design (CAD) model of the smart valve was prepared with Solidworks software (Figure a) and printed with an Envisiontec 3D‐Bioplotter (Figure b).…”

Section: Resultsmentioning

confidence: 99%

4D Printing with Mechanically Robust, Thermally Actuating Hydrogels

Bakarich

Gorkin

Panhuis

et al. 2015

Macromol. Rapid Commun.

471

270

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Hydrogels were utilized as the active material in the 4D printed structures since these materials have been processed with printers [ 8 ] and some examples of hydrogels can drastically, and reversibly, alter their volume in response to changes within their environment. [ 9,10 ] We start with an ionic covalent entanglement (ICE) hydrogel [ 11 ] that can be 3D printed [ 12 ] and demonstrate high toughness. [ 12 ] The latter is important since we require thin sections that respond quickly to external stimuli but also need to be mechanically robust to support the internal and external mechanical loads. ICE gels are a type of an interpenetrating polymer network hydrogel that is made up of an entanglement of one polymer network crosslinked with metal cations and a second polymer network crosslinked with covalent bonds. [ 11,[13][14][15] This dual network structure is similar to that in double network hydrogels [ 16,17 ] and facilitates high toughness through large-scale crack-tip energy dissipation by unloading of the strands in the tight network, [ 18 ] in this case due to dissociation of the ionic crosslinks. [ 19 ] The loosely crosslinked covalent network serves to bridge the damage zones created by the loss of ionic bonds and prevents catastrophic crack propagation. Here, we use a thermally responsive covalent crosslinked network of poly( N -isopropylacrylamide) (PNIPAAm) to function as both the toughening agent and to provide actuation through reversible volume transitions. PNIPAAm is a widely studied temperature-sensitive hydrogel that exhibits a large reversible volume transition at a critical temperature, T C (≈32-35 °C). [ 20,21 ] The volume change is caused by a coil-globule transition of the polymer network strands [ 22 ] and results in a large decrease in the water content when the temperature is increased above T c . [ 20 ] Results and DiscussionAlginate/PNIPAAm ICE gel inks with various concentrations of NIPAAm were prepared for extrusion printing.

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Section: Resultsmentioning

confidence: 99%

4D Printing with Mechanically Robust, Thermally Actuating Hydrogels

Bakarich

Gorkin

Panhuis

et al. 2015

Macromol. Rapid Commun.

471

270

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“…Over the last 2 decades, the capabilities of microfluidics have been expanded to sample pumps, valves, storage, and mixers . Unlike discrete sampling at specific time points, microfluidic enables continuous fluid analyses .…”

Section: Resultsmentioning

confidence: 99%

Microfluidic Contact Lenses

Jiang

Montelongo

Butt

et al. 2018

Small

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Contact lens is a ubiquitous technology used for vision correction and cosmetics. Sensing in contact lenses has emerged as a potential platform for minimally invasive point-of-care diagnostics. Here, a microlithography method is developed to fabricate microconcavities and microchannels in a hydrogel-based contact lens via a combination of laser patterning and embedded templating. Optical microlithography parameters influencing the formation of microconcavities including ablation power (4.3 W) and beam speed (50 mm s ) are optimized to control the microconcavity depth (100 µm) and diameter (1.5 mm). The fiber templating method allows the production of microchannels having a diameter range of 100-150 µm. Leak-proof microchannel and microconcavity connections in contact lenses are validated through flow testing of artificial tear containing fluorescent microbeads (Ø = 1-2 µm). The microconcavities of contact lenses are functionalized with multiplexed fluorophores (2 µL) to demonstrate optical excitation and emission capability within the visible spectrum. The fabricated microfluidic contact lenses may have applications in ophthalmic monitoring of metabolic disorders at point-of-care settings and controlled drug release for therapeutics.

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“…Some examples of devices with integrated reversible valves include the use of thermoresponsive ionogel 24 and PDMS micromechanical valves; 25 however these have very limited lifetimes. Multiple sampling creates a need for highly robust and reversible valving mechanisms, in order to minimize the number of pumps and the platform footprint.…”

Section: Introductionmentioning

confidence: 99%

Real-time direct cell concentration and viability determination using a fully automated microfluidic platform for standalone process monitoring

Nunes

Kjærulff²,

Dufva

et al. 2015

Analyst

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The industrial production of cells has a large unmet need for greater process monitoring, in addition to the standard temperature, pH and oxygen concentration determination. Monitoring the cell health by a vast range of fluorescence cell-based assays can greatly improve the feedback control and thereby ensure optimal cell production, by prolonging the fermentation cycle and increasing the bioreactor output. In this work, we report on the development of a fully automated microfluidic system capable of extracting samples directly from a bioreactor, diluting the sample, staining the cells, and determining the total cell and dead cells concentrations, within a time frame of 10.3 min. The platform consists of custom made stepper motor actuated peristaltic pumps and valves, fluidic interconnections, sample to waste liquid management and image cytometry-based detection. The total concentration of cells is determined by brightfield microscopy, while fluorescence detection is used to detect propidium iodide stained non-viable cells. This method can be incorporated into facilities with bioreactors to monitor the cell concentration and viability during the cultivation process. Here, we demonstrate the microfluidic system performance by monitoring in real time the cell concentration and viability of yeast extracted directly from an in-house made bioreactor. This is the first demonstration of using the Dean drag force, generated due to the implementation of a curved microchannel geometry in conjunction with high flow rates, to promote passive mixing of cell samples and thus homogenization of the diluted cell plug. The autonomous operation of the fluidics furthermore allows implementation of intelligent protocols for administering air bubbles from the bioreactor in the microfluidic system, so that these will be guided away from the imaging region, thereby significantly improving both the robustness of the system and the quality of the data.

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Modular microfluidic valve structures based on reversible thermoresponsive ionogel actuators

Cited by 57 publications

References 30 publications

4D Printing with Mechanically Robust, Thermally Actuating Hydrogels

4D Printing with Mechanically Robust, Thermally Actuating Hydrogels

Microfluidic Contact Lenses

Real-time direct cell concentration and viability determination using a fully automated microfluidic platform for standalone process monitoring

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