Microprinted feeder cells guide embryonic stem cell fate

We introduce a non‐contact approach to microprint multiple types of feeder cells in a microarray format using immiscible aqueous solutions of two biopolymers. Droplets of cell suspension in the denser aqueous phase are printed on a substrate residing within a bath of the immersion aqueous phase. Due to their affinity to the denser phase, cells remain localized within the drops and adhere to regions of the substrate underneath the drops. We show the utility of this technology for creating duplex heterocellular stem cell niches by printing two different support cell types on a gel surface and overlaying them with mouse embryonic stem cells (mESCs). As desired, the type of printed support cell spatially direct the fate of overlaid mESCs. Interestingly, we found that interspaced mESCs colonies on differentiation‐inducing feeder cells show enhanced neuronal differentiation and give rise to dense networks of neurons. This cell printing technology provides unprecedented capabilities to efficiently identify the role of various feeder cells in guiding the fate of stem cells. Biotechnol. Bioeng. 2011;108: 2509–2516. © 2011 Wiley Periodicals, Inc.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/86949/1/23190_ftp.pd

Transwells with Microstamped Membranes Produce Micropatterned Two-Dimensional and Three-Dimensional Co-Cultures

This article describes a simple and rapid cell patterning method to form co-culture microarrays in commercially available Transwells. A thin poly(dimethylsiloxane) (PDMS) layer is printed on the underside of a Transwell using a PDMS stamp. Arbitrary cellular patterns are generated according to the geometric features of the thin PDMS layer through hydrodynamic forces that guide cells onto the membrane only over the PDMS-uncoated regions. Micropatterns of surface-adhered cells (we refer to this as two-dimensional) or non-surface-adhered clusters of cells (we refer to this as three-dimensional) can be generated depending on the surface treatment of the filter membrane. Additionally, co-cultures can be established by introducing different types of cells on the membrane or in the bottom chamber of the Transwell. We show that this co-culture method can evaluate mouse embryonic stem (mES) cell differentiation based on heterogeneous cell-cell interactions. Co-culture of mES cells and HepG2 cells decreased SOX17 expression of mES cells, and direct cell-cell contact further decreased SOX17 expression, indicating that co-culture with HepG2 cells inhibits endoderm differentiation through soluble factors and cell-cell contact. This method is simple and user-friendly and should be broadly useful to study cell shapes and cell-cell interactions.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/90499/1/ten-2Etec-2E2010-2E0305.pd

Polymer-based mesh as supports for multi-layered 3D cell culture and assays

Three-dimensional (3D) culture systems can mimic certain aspects of the cellular microenvironment found in vivo, but generation, analysis and imaging of current model systems for 3D cellular constructs and tissues remain challenging. This work demonstrates a 3D culture system–Cells-in-Gels-in-Mesh (CiGiM)–that uses stacked sheets of polymer-based mesh to support cells embedded in gels to form tissue-like constructs; the stacked sheets can be disassembled by peeling the sheets apart to analyze cultured cells—layer-by-layer—within the construct. The mesh sheets leave openings large enough for light to pass through with minimal scattering, and thus allowing multiple options for analysis—(i) using straightforward analysis by optical light microscopy, (ii) by high-resolution analysis with fluorescence microscopy, or (iii) with a fluorescence gel scanner. The sheets can be patterned into separate zones with paraffin film-based decals, in order to conduct multiple experiments in parallel; the paraffin-based decal films also block lateral diffusion of oxygen effectively. CiGiM simplifies the generation and analysis of 3D culture without compromising throughput, and quality of the data collected: it is especially useful in experiments that require control of oxygen levels, and isolation of adjacent wells in a multi-zone format.Chemistry and Chemical Biolog

Three-Dimensional Paper-Based Model for Cardiac Ischemia

In vitro models of ischemia have not historically recapitulated the cellular interactions and gradients of molecules that occur in a 3D tissue. This work demonstrates a paper-based 3D culture system that mimics some of the interactions that occur among populations of cells in the heart during ischemia. Multiple layers of paper containing cells, suspended in hydrogels, are stacked to form a layered 3D model of a tissue. Mass transport of oxygen and glucose into this 3D system can be modulated to induce an ischemic environment in the bottom layers of the stack. This ischemic stress induces cardiomyocytes at the bottom of the stack to secrete chemokines which subsequently trigger fibroblasts residing in adjacent layers to migrate toward the ischemic region. This work demonstrates the usefulness of patterned, stacked paper for performing in vitro mechanistic studies of cellular motility and viability within a model of the laminar ventricle tissue of the heart.Chemistry and Chemical BiologyEngineering and Applied SciencesOther Research Uni

An integrated design and fabrication strategy for entirely soft, autonomous robots

Soft robots possess many attributes that are difficult, if not impossible, to realize with conventional robots composed of rigid materials. Yet, despite recent advances, soft robots still remain tethered to hard robotic control systems and power sources. New strategies for creating completely soft robots, including soft analogs of these crucial components, are needed to realize their full potential. Here, we report the first untethered operation of a robot comprised solely of soft materials. The robot is controlled with microfluidic logic that autonomously regulates the catalytic decomposition of an on-board monopropellant fuel supply. Gas generated from fuel decomposition inflates fluidic networks downstream of the reaction sites, resulting in actuation. The robot’s body and microfluidic logic are fabricated by molding and soft lithography, respectively, while the pneumatic actuator networks, on-board fuel reservoirs and catalytic reaction chambers needed for movement are patterned within the body via a multi-material, embedded 3D printing technique. The relevant length scales of fluidic and elastomeric architectures required for function spanned several orders of magnitude. Our integrated design and rapid fabrication approach enables the programmable assembly of multiple materials within this architecture, laying the foundation for completely soft, autonomous robots.Chemistry and Chemical BiologyEngineering and Applied Science

Buckling of Elastomeric Beams Enables Actuation of Soft Machines

Soft, pneumatic actuators that buckle when interior pressure is less than exterior provide a new mechanism of actuation. Upon application of negative pneumatic pressure, elastic beam elements in these actuators undergo reversible, cooperative collapse, and generate a rotational motion. These actuators are inexpensive to fabricate, lightweight, easy to control, and safe to operate. They can be used in devices that manipulate objects, locomote, or interact cooperatively with humans.Chemistry and Chemical Biolog

A Resilient, Untethered Soft Robot

A pneumatically powered, fully untethered mobile soft robot is described. Composites consisting of silicone elastomer, polyaramid fabric, and hollow glass microspheres were used to fabricate a sufficiently large soft robot to carry the miniature air compressors, battery, valves, and controller needed for autonomous operation. Fabrication techniques were developed to mold a 0.65-meter-long soft body with modified Pneu-Net actuators capable of operating at the elevated pressures (up to 138 kPa) required to actuate the legs of the robot and hold payloads of up to 8 kg. The soft robot is safe to interact with during operation, and its silicone body is innately resilient to a variety of adverse environmental conditions including snow, puddles of water, direct (albeit limited) exposure to flames, and the crushing force of being run over by an automobile.Chemistry and Chemical Biolog

Folding Analytical Devices for Electrochemical ELISA in Hydrophobic R H Paper

This work describes a device for electrochemical enzyme-linked immunosorbent assay (ELISA) designed for low-resource settings and diagnostics at the point of care. The device is fabricated entirely in hydrophobic paper, produced by silanization of paper with decyl trichlorosilane, and comprises two zones separated by a central crease: an embossed microwell, on the surface of which the antigen or antibody immobilization and recognition events occur, and a detection zone where the electrodes are printed. The two zones are brought in contact by folding the device along this central crease; the analytical signal is recorded from the folded configuration. Two proof-of-concept applications, an electrochemical direct ELISA for the detection of rabbit IgG as a model antigen in buffer and an electrochemical sandwich ELISA for the detection of malarial histidine-rich protein from Plasmodium falciparum (Pf HRP2) in spiked human serum, show the versatility of this device. The limit of detection of the electrochemical sandwich ELISA for the quantification of Pf HRP2 in spiked human serum was 4 ng mL–1 (102 pmol L–1), a value within the range of clinically relevant concentrations.Chemistry and Chemical Biolog

Buckling Pneumatic Linear Actuators Inspired by Muscle

The mechanical features of biological muscles are difficult to reproduce completely in synthetic systems. A new class of soft pneumatic structures (vacuum-actuated muscle-inspired pneumatic structures) is described that combines actuation by negative pressure (vacuum), with cooperative buckling of beams fabricated in a slab of elastomer, to achieve motion and demonstrate many features that are similar to that of mammalian muscle.Chemistry and Chemical Biolog

Magnetic Assembly of Soft Robots with Hard Components

This paper describes the modular magnetic assembly of reconfigurable, pneumatically actuated robots composed of soft and hard components and materials. The soft components of these hybrid robots are actuators fabricated from silicone elastomers using soft lithography,and the hard components are acrylonitrile-butadiene-styrene (ABS) structures made using three-dimensional (3D) printing. Neodymium-iron-boron (NdFeB) ring magnets are embedded in these components to make and maintain the connections between components. The reversibility of these magnetic connections allows the rapid reconfiguration of these robots using components made of different materials (soft and hard) that also have different sizes, structures, and functions; in addition, it accelerates the testing of new designs, the exploration of new capabilities, and the repair or replacement of damaged parts. This method of assembling soft actuators to build soft machines addresses some limitations associated with using soft lithography for the direct molding of complex 3D pneumatic networks. Combining the self-aligning property of magnets with pneumatic control makes it possible for a teleoperator to modify the structures and capabilities of these robots readily in response to the requirements of different tasks.Physic