PMC

(a) This device consists of three layers, a gel layer to support adherent cell culture, a micropatterned nanoporous membrane layer and a microfluidic layer made by PDMS. (b) Compounds of interest can be loaded into the microchannel patterned on PDMS layer and spatially located into the gel layer through the nanoporous membrane upon an electric field.

(a) Schematic of a printing system. A valve-based ejector is connected with a 3D stage which offers ejection of cell encapsulating droplets (e.g., hydrogels) high spatial resolution. (b) The droplets can be pattend in an array format on a substrate (e.g., Petri dish, glass slides). (c) A sample of high-density cell microarrays.

(a) Alginate dip-coated in a Nylon mesh is stamped on a cell adhesive substrate (e.g., glass). Alginate is crosslinked after water evaporation with a solution of calcium chloride forming hydrogel spots. The cell microarray is achieved by seeding cells within the hydrogel compartments. (b) A fibroblast array with density of 21,000/cm² was achieved using this method (24 hours in culture).

The stamping method consists of three main steps to achieve precise drug loading. (a) Compounds of interest are spotted on an array chip (Metachip). (b) Cells are grown on a PDMS base, defined as a cell array (DataChip). (c) The array chip and DataChip are stamped together to allow for perfusion. The toxicity of compounds on cells is evaluated using live/dead staining on the cell array. Each cell spot has diameter of 600 μm.

Generally, pattern is designed and a photomask is fabricated based on design. The mask is then used to fabricate the master on a silicon wafer via lithography. The silicon wafer master can be used repeatedly as a mold for casting PDMS stamps. The PDMS stamp containing protruding columns is pressed onto another hydrogel solution (e.g., PEG monomer solution) on a glass slide. Microwells array is formed by UV cross-linking of PEG and removing the PDMS stamp from the formed microwells. Cells are seeded to microwells to form cell microarrays.

(a) Time-multiplexed, 3D arrays of optical traps were used to manipulate cells. The optical traps were created using infrared light (red path) from a Ti:sapphire laser beam. A microfluidic network is used to deliver the multiple types of cells mixed with hydrogel precursor to the assembly area: two types of cells (E. coli RFP, E. coli GFP) flow in different channels with a third cell-free channel in middle. In the assembly area, the cells are encapsulated within the hydrogel through photo crosslinking forming cell array (b, 2D 5 × 6 microarray). (c) Nine homogeneous 4 × 4 microarrays of G1 E. coli forming a 3 × 3 microarray.