Embryonic stem cells serve as powerful models for the study of development and disease and hold enormous potential for future therapeutics. Yet, over two decades after mouse embryonic stem cells (mESCs) were first isolated, there is still little known abouthe role of cell-cell signaling in self-renewal. Since traditional cell-culture techniques do not provide significant control of the stem cell microenvironment, thegoal of this thesis was to develop a cell patterning technology that allows us to precisely control stem cell signaling and monitor cell proliferation over time.

In the first aim of this thesis, we describe the development of our first cell patterning technology using dielectrophoresis (DEP). DEP uses nonuniform electric fields to trap cells on or between electrodes. We first used beads as model particles to validate the strength of our DEP square trap, and then demonstrated efficient cell patterning with multiple cell types.

In the second aim of this thesis, we describe the development of a novel cell patterning technology that we created, called the Bio Flip Chip (BFC). The BFC is a microfabricated polymer chip, containing thousands of microwells, that enables cell patterning with single-cell resolution anywhere on a substrate and onto any substrate.

In the last aim of this thesis, we used our BFC technology to control the stem cell microenvironment, allowing us to incrementally and independently modulate cell-cell contact. We present the first quantitative evidence that cell-cell contact depresses mESC colony formation and show that E-cadherin signaling is responsible for this negative regulatory pathw