Self-loading lithographically structured microcontainers: 3D patterned, mobile microwells

Abstract

We demonstrate mass-producible, mobile, self-loading microcontainers that can be used to encapsulate both non-living and living objects, thus forming three-dimensionally patterned, mobile microwells.Studies of cells and their function have traditionally been performed on two-dimensional (2D) cell cultures. However, the omission of the third dimension can greatly impact cell behavior by limiting interactions with the surroundings. 1 Microwells in substrates have been developed to address this, but are typically accessible only from one interface; this limitation is especially pronounced in cell culture when the encapsulated cells may experience nutrient deficient conditions due to well geometry and size. 2Researchers continue to add new functionality to microwells, such as making them compatible with high resolution analysis, adding networking channels to facilitate cell-cell interactions, integrating stimulation/measurement devices, and devising methods to generate dense arrays of wells with individually customizable, variable geometry morphologies. 3,4 Also, microwell structures for bioreactors have been designed with porous membrane floors that allow for media perfusion through the well. 5 This allows media to convectively enter the microwell from one interface and exit through another. However, despite the advancements in technology, current microwells essentially only provide a quasi-3D environment, where patterning is limited to 2D and cells are in contact with planar surfaces. 3 Truly 3D encapsulation, where porosity is precisely engineered on all faces in 3D, allows for greater interaction between encapsulated cells and surrounding media.In this communication, we describe photolithographically structured, mobile microcontainers that function like three-dimensionally patterned, mobile microwells. The containers load themselves as they self-assemble from cruciform templates en masse at around 40°C, a temperature low enough to enable parallel loading of biological objects. These containers have porous surfaces and interact with their surroundings in all three dimensions. Additionally, the untethered nature of the cruciforms and containers, coupled with the use of ferromagnetic materials, allows for remote-controlled guidance of both unloaded cruciforms as well as loaded containers. 7 The assembly of the microcontainers is thermally triggered, without the need for any external connections. Photolithography enables the containers to be fabricated with precisely-engineered monodisperse sizes, shapes, and wall porosity. 6 Using self-assembly, 2D templates are transformed into 3D structures with porosity in all dimensions. We demonstrate the self-loading of glass beads, L929 fibroblast cells, and Triops embryos. The loading of biological contents highlights the utility of the low temperature self-loading process.Fabrication of the microcontainers was based on stress-driven assembly using thin film hinges and has been described in detail elsewhere. 8 Briefly, the microcontainers were constructed as 2D cru...

Laser printing hierarchical structures with the aid of controlled capillary-driven self-assembly

“…Although optical tweezers are able to manipulate small objects with different sizes ranging from tens of nanometers to micrometers, a substantial mechanical gripper is still desired in the absence of an energy beam and free of possible harm to living samples or influences to chemical reactions. Examples include miniaturized self-folding grippers that are actuated by differential residual stress (33), magnetic force (34), temperature (35,36), and chemicals (37,38). We show here our LPCS artificial fibrillar structures are capable of capturing microparticles with excellent selectivity.…”

Fabrication of 3D Cellular Tissue Utilizing MEMS Technologies

“…The advantages of the planar microparts are handleability of adherent cells maintaining cellular adhesions and morphology, and applicability for the assembly of spatially-controlled 3D structures. Conventional micro-object handling techniques are applicable such as microfluidic techniques [36][37][38][39][40][41], micromanipulation techniques [42][43][44], chemical/physical cell-patterning techniques [45][46][47][48], and self assembly techniques [13,[49][50][51]. These advantages open the path for the fabrication of spatially-controlled heterogeneous 3D cellular tissue models.…”

Self-Assembly in Micro- and Nanofluidic Devices: A Review of Recent Efforts

“…The localized remote-controlled chemical delivery establishes a methodology for remotely manipulating the chemical and biological micro-environment for applications in cell engineering, tissue engineering, and drug development. A similar technology was applied to demonstrate a low temperature method for enabling truly three dimensional encapsulations of cells, embryos, and eggs with porosity that can be precisely engineered on all faces in three dimensions that facilitates better transport of media and nutrients [37].…”

“…Ye et al has successfully combined microfabricated nanoliter scale fluidic devices with wireless technology by fabricating remote-controlled cubic microcontainers for temporal and spatial chemical delivery [37]. The gold-coated, nickel nanoliter containers were fabricated based on a combination of conventional microfabrication and self-assembly [77,78].…”

“…When a microfluidic device is coupled with the free-flow self-assembly method, a range of three dimensional micro-and nanoparticle crystalline structures can be formed [13,33]. A variety of interesting applications to assemble a range of organic and inorganic micro-and nanomaterials has been demonstrated including the construction of two dimensional devices such as micropump (superparamagnetic microparticles) [34], on-board electronic packaging (semiconductor microdevice) [35], nanoelectronics (carbon nanotubes) [36], tunable plasmonic waveguides (gold and silver nanoparticles) [25] and three dimensional devices such as anticancer drug tester (multicellular spheroids) [27], drug delivery microcontainer (metallic plates) [37], molecular sieving system (silica nanoparticles) [13], etc.…”