Liyuan Zhang

1. Encapsulation and controlled release.

Controlled deliver and release molecules have a huge application such as pharmacology, cosmetic and drug delivery. However, precise release the molecules is difficult to realize. We in the lab apply microfluidic technology and generate picoliter-sized particles or capsules through single or double emulsions as the template. Interesting materials are encapsulated in the core, we control the release behavior by fine tuning the shell thickness, and its compositions. We also try to develop new materials that would be suitable for sensitive molecules encapsulation and release. For example, we encapsulate antibodies in a degradable PLGA shell that can be injected in the patient and finely release inside. We can also encapsulate small molecular or liquid metal for the detection of electronic property variations.

Microcapule release its encapulant under stimuli

Figure 1  Microcapule release its encapulant under stimuli.

2. Cell in gel

Stem cells are becoming one of the most promising forms of therapy in tissue engineering and stem cell therapy due to its differentiation into various types of cells. Stem cell can be collected directly, engineered and injected back into patients as a key component of immunotherapy. However, the efficacy of cell-based therapies depends on materials science. While directly injecting cell into patient, these cells are not very effective in performing their tasks. The vital reason is that the immune cell response from the patient, which makes this process very inefficient. This presents a major impediment to the widespread success of cell-based therapies. Hydrogel is a three-dimensional material possessing pores that large enough to transmit small ions but small enough to block the attack from immune attach. In the lab, we have developed a microfluidic based method that can successfully encapsulate stem cell with minimum damage to the cell, and we study their behavior both in vitro and in vitro. Currently, we can maintain cell viability as high as 99%, and we also design different device to study the cell-cell interaction at single cell level. Moreover, to validate its capability in tissue repair, we delivery the gel encapsulated cells in mouse for the osteogenesis.

Cell encapsulation process.

Figure 2 Cell encapsulation process.

3. Nanoparticles for unconventional oil recovery

Most of the residual oil lies in low permeability region in the deep zone of the oil reservoir after secondary recovery. However, due to the heterogeneity of the oil reservoir, water preferential channels are easily formed, which decrease the sweep efficiency, leaving the crude oil in the low permeability region. Polyacrylamide particles are applied and can be injected into the oil reservoir, blocking the high permeability region and forcing the flow goes into the low permeability region. These particles are hydrophilic that can swell after immersing in water in a short period of time, which limits their application in oil recovery. One of my research is to develop a new type of “smart” nanoparticles with delayed swelling behavior, which can be injected into the low permeable region and change the conformance of the medium. We have invented a new method that can synthesize core-shell particle with polyacrylamide core and a degradable shell. By controlling the degradation behavior of the shell, we can fine control the swelling of the shell in the brine. These particles can swell up to 270 time compared with their original volume, which can block the pore throat of the medium. Core flooding experiment shows that particles successfully block the pore throat with the evident of the low permeability. We now seeking the new method to scale up these particles. Besides, the mechanism of particles swelling, the particles transportation behavior in the porous medium, and the oil recovery mechanism while using nanoparticle.

Conformance control using nanohydrogel
Conformance control using nanohydrogel

Figure 3 Conformance control using nanohydrogel

Contact: Liyuan Zhang