Qiancheng Zhang

Engineering three-dimensional cell mechanical microenvironment with hydrogels.

Cell mechanical microenvironment (CMM) significantly affects cell behaviors such as spreading, migration, proliferation and differentiation. However, most studies on cell response to mechanical stimulation are based on two-dimensional (2D) planar substrates, which cannot mimic native three-dimensional (3D) CMM. Accumulating evidence has shown that there is a significant difference in cell behavior in 2D and 3D microenvironments. Among the materials used for engineering 3D CMM, hydrogels have gained increasing attention due to their tunable properties (e.g. chemical and mechanical properties). In this paper, we provide an overview of recent advances in engineering hydrogel-based 3D CMM. Effects of mechanical cues (e.g. hydrogel stiffness and externally induced stress/strain in hydrogels) on cell behaviors are described. A variety of approaches to load mechanical stimuli in 3D hydrogel-based constructs are also discussed.

Cell-encapsulating microfluidic hydrogels with enhanced mechanical stability

Whilst microfluidic hydrogels find broad applications in multiple fields such as tissue engineering and regenerative medicine, it has been challenging to sustain the microfluidic structure of most hydrogels due to their insufficient mechanical properties. In this study, we presented a simple method to fabricate microfluidic hydrogels with mechanically enhanced microchannels by using interpenetrating polymer network hydrogels composed of agarose and poly(ethylene glycol) (PEG). The microchannels within the hydrogels were mechanically enhanced with additional PEG layer. Both experimental and numerical results indicated that the mechanically enhanced PEG layer along the microchannels improved the resistance to deformation under compressive loading relative to controls (i.e., without enhanced channel walls). We further assessed the diffusion properties and viability of cells encapsulated within the hydrogels, which showed no significant difference between the enhanced and control groups. The microfluidic hydrogel fabrication approach developed here holds great potential to impact a wide range of fields, such as microfluidics, tissue engineering and regenerative medicine.

Effect of pore morphology on cross-property link for close-celled metallic foams

We demonstrate a simple cross-property correlation between effective conductivity (both thermal and electrical) and effective elastic modulus for high porosity cellular metallic foams with non-spherical closed cells. A particular solution to the equation of Laplace heat conduction for modelling foam thermal conductivity is extended to account for non-spherical gaseous pores; and this model is further associated with the estimation of effective elastic modulus. The simple cross-property correlation thus obtained shows that both the effective conductivity and modulus significantly decrease with increasing porosity. Non-spherical pores contribute to further reduce the effective conductivity and modulus, due mainly to increased tortuosity and stress concentration caused by enlarged surface area and sharp corners as spherical pores are replaced by non-spherical ones.