| 1. |
- Khaldi, Alexandre, 1982-, et al.
(författare)
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Patterning highly conducting conjugated polymer electrodes for soft and flexible microelectrochemical devices
- 2018
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Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 10:17, s. 14978-14985
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Tidskriftsartikel (refereegranskat)abstract
- There is a need for soft actuators in various biomedical applications in order to manipulate delicate objects such as cells and tissues. Soft actuators are able to adapt to any shape and limit the stress applied to delicate objects. Conjugated polymer actuators, especially in the so-called trilayer configuration, are interesting candidates for driving such micromanipulators. However, challenges involved in patterning the electrodes in a trilayer with individual contact have prevented further development of soft micromanipulators based on conjugated polymer actuators. To allow such patterning, two printing-based patterning techniques have been developed. First an oxidant layer is printed using either syringe-based printing or micro-contact printing, followed by vapor phase polymerization of the conjugated polymer. Sub-millimeter patterns with electronic conductivities of 800 Scm-1 are obtained. Next, laser ablation is used to cleanly cut the final device structures including the printed patterns, resulting in fingers with individually controllable digits and miniaturized hands. The methods presented in this paper will enable integration of patterned electrically active conjugated polymer layers in many types of complex 3-D structures.
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| 2. |
- Baumgartner, Johanna, et al.
(författare)
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Switchable presentation of cytokines on electroactive polypyrrole surfaces for hematopoietic stem and progenitor cells
- 2018
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Ingår i: Journal of Materials Chemistry B. - Cambridge : Royal Society of Chemistry. - 2050-750X .- 2050-7518. ; 6:28, s. 4665-4675
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Tidskriftsartikel (refereegranskat)abstract
- Hematopoietic stem cells are used in transplantations for patients with hematologic malignancies. Scarce sources require efficient strategies of expansion, including polymeric biomaterials mimicking architectures of bone marrow tissue. Tissue microenvironment and mode of cytokine presentation strongly influence cell fate. Although several cytokines with different functions as soluble or membrane-bound mediators have already been identified, their precise roles have not yet been clarified. A need exists for in vitro systems that mimic the in vivo situation to enable such studies. One way is to establish surfaces mimicking physiological presentation using protein-immobilization onto polymer films. However these films merely provide a static presentation of the immobilized proteins. It would be advantageous to also dynamically change protein presentation and functionality to better reflect the in vivo conditions. The electroactive polymer polypyrrole shows excellent biocompatibility and electrochemically alters its surface properties, becoming an interesting choice for such setups. Here, we present an in vitro system for switchable presentation of membrane-bound cytokines. We use interleukin IL-3, known to affect hematopoiesis, and show that when immobilized on polypyrrole films, IL-3 is bioavailable for the bone marrow-derived FDC-P1 progenitor cell line. Moreover, IL-3 presentation can be successfully altered by changing the redox state of the film, in turn influencing FDC-P1 cell viability. This novel in vitro system provides a valuable tool for stimuli-responsive switchable protein presentation allowing the dissection of relevant mediators in stem and progenitor cell behavior.
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| 3. |
- Cao, Danfeng, 1991-, et al.
(författare)
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Soft actuators that self-create bone for biohybrid (micro)robotics
- 2022
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Ingår i: Proceedings of The 5th International Conference on Manipulation, Automation, And Robotics at Small Scales (MARSS 2022). - : Institute of Electrical and Electronics Engineers (IEEE). - 9781665459730 - 9781665459747 ; , s. 1-6
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Konferensbidrag (refereegranskat)abstract
- Here we present a new class of variable stiffness actuators for soft robotics based on biohybrid materials that change their state from soft-to-hard by creating their own bones. The biohybrid variable stiffness soft actuators were fabricated by combining the electromechanically active polymer polypyrrole (PPy) with a soft substrate of polydimethylsiloxane or alginate gel. These actuators were functionalized with cell-derived plasma membrane nanofragments (PMNFs), which promote rapid mineralization within 2 days. These actuators were used in robotic devices, and PMNF mineralization resulted in the robotic devices to achieve a soft to stiff state change and thereby a decreased or stopped actuation. Moreover, perpendicularly and diagonally patterned actuators were prepared. The patterned actuators showed programmed directional actuation motion and could be fixated in this programmed state. Finally, patterned actuators that combined soft and rigid parts in one actuator showed more complex actuation motion. Together, these variable stiffness actuators could expand the range of applications of morphing robotics with more complex structures and functions.
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| 4. |
- Guan, Na N., et al.
(författare)
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The role of ATP signalling in response to mechanical stimulation studied in T24 cells using new microphysiological tools
- 2018
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Ingår i: Journal of Cellular and Molecular Medicine. - : Wiley. - 1582-1838 .- 1582-4934. ; 22:4, s. 2319-2328
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Tidskriftsartikel (refereegranskat)abstract
- The capacity to store urine and initiate voiding is a valued characteristic of the human urinary bladder. To maintain this feature, it is necessary that the bladder can sense when it is full and when it is time to void. The bladder has a specialized epithelium called urothelium that is believed to be important for its sensory function. It has been suggested that autocrine ATP signalling contributes to this sensory function of the urothelium. There is well‐established evidence that ATP is released via vesicular exocytosis as well as by pannexin hemichannels upon mechanical stimulation. However, there are still many details that need elucidation and therefore there is a need for the development of new tools to further explore this fascinating field. In this work, we use new microphysiological systems to study mechanostimulation at a cellular level: a mechanostimulation microchip and a silicone‐based cell stretcher. Using these tools, we show that ATP is released upon cell stretching and that extracellular ATP contributes to a major part of Ca2+ signalling induced by stretching in T24 cells. These results contribute to the increasing body of evidence for ATP signalling as an important component for the sensory function of urothelial cells. This encourages the development of drugs targeting P2 receptors to relieve suffering from overactive bladder disorder and incontinence.
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| 5. |
- Jager, Edwin W. H., 1973-
(författare)
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Microsystems based on polypyrrole microactuators : microrobots and cell clinics
- 2001
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Conducting polymers like polypyrrole (PPy) are suitable materials for actuators. PPy undergoes a volume change, driven by redox processes accompanied by ion movement. This volume change is reversible. By combining PPy with a support and/or electrode layer into a bilayer, actuators can be made. These actuators are operated in a liquid electrolyte. The microactuators presented in this thesis are based on an Au/PPy bilayer in which the Au acts both as a structural layer and electrode. PPy doped with DBS- ( dodecylbenzenesulfonate) anions (PPy(DBS)) is used and the microactuators are operated in an aqueous salt solution, usually NaDBS. However, the microactuators function also in other biological more relevant media, like blood plasma, urine, and cell culture media, making them excellent tools for cell biology and biomedicine. The thesis is focussed on methods to microfabricate devices, and their operation and use.PPy/Au microactuators, which have all the electrodes necessary for the actuation --the working, counter, and reference electrodes -- on-chip, were developed. The microactuators' performance was as good as when standard, off-chip counter and reference electrodes were used. Specifically, the speed of actuation was the same.A novel microfabrication method based on a Ti sacrificial layer was developed in order to create individually addressable and controllable polypyrrole-gold microactuators. Using these individually controlled microactuators, a micrometer-sized manipulator or microrobotic arm was fabricated. This microrobotic arm can pick up, lift, move, and place micrometer-sized objects within an area of about 250 x 100 μm2, making the microrobot an excellent tool for single cell manipulation. Also, these individually controlled microactuators were used to obtain movements both out of and in the plane of the substrate surface. A scheme to make true three-dimensional movements is demonstrated.Finally, the development of a cell clinic is presented. This is a micromachined cavity, or microvial, that can be closed with a lid. The lid is activated by two PPy/Au microactuators. A pair of Au electrodes was placed inside the microvials in order to perform impedance studies on single or a small number of cells. Impedance measurements on Xenopus leavis melanophores are reported. A change in the impedance upon cell spreading was measured and intracellular events such as the aggregation of pigment granules were identified. The electrical data are correlated to optical microscopy.
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| 6. |
- Vagin, Mikhail Yu., et al.
(författare)
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Water-processable polypyrrole microparticle modules for direct fabrication of hierarchical structured electrochemical interfaces
- 2016
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Ingår i: Electrochimica Acta. - : Elsevier. - 0013-4686 .- 1873-3859. ; 190, s. 495-503
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Tidskriftsartikel (refereegranskat)abstract
- Hierarchically structured materials (HSMs) are becoming increasingly important in catalysis, separation and energy applications due to their advantageous diffusion and flux properties. Here, we introduce a facile modular approach to fabricate HSMs with tailored functional conducting polypyrrole microparticles (PPyMP). The PPyMPs were fabricated with a calcium carbonate (CaCO3) template-assisted polymerization technique in aqueous media at room temperature, thus providing a new green chemistry for producing water-processable functional polymers. The sacrificial CaCO3 template guided the polymerization process to yield homogenous PPyMPs with a narrow size distribution. The porous nature of the CaCO3 further allows the incorporation of various organic and inorganic dopants such as an electrocatalyst and redox mediator for the fabrication of functional PPyMPs. Dawson-type polyoxometalate (POM) and methylene blue (MB) were chosen as the model electrocatalyst and electron mediator dopant, respectively. Hierarchically structured electrochemical interfaces were created simply by self-assembly of the functional PPyMPs. We demonstrate the versatility of this technique by creating two different hierarchical structured electrochemical interfaces: POM-PPyMPs for hydrogen peroxide electrocatalysis and MB-PPyMPs for mediated bioelectrocatalysis. We envision that the presented design concept could be extended to different conducting polymers doped with other functional organic and inorganic dopants to develop advanced electrochemical interfaces and to create high surface area electrodes for energy storage.
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