Fig. 13.

(a) Shape-encoded assembly of magnetic microactuators to a non-magnetic body fabricated with direct laser writing. (i–ii) A 3D microcar body with four-wheel pockets is designed to generate site-selective attractive DEP forces toward ​the wheel pockets. Color bar: normalized electric field strength (E/E₀)². (iii) Directed assembly of the magnetic microactuators into the wheel pockets is realized on-demand using DEP. (iv) The microcar translates under a vertically rotating magnetic field and is steered by changing the rotation axis of the magnetic field. (v) The microrotor body and magnetic microbeads are coupled together with DEP and rotate when a horizontally rotating magnetic field in the x–y plane is applied. Scale bars, 25 ​μm [48]. (b) Patterning biological and physical aspects of a stem cell niche in a microrobotic cell transporter (MCT). (i) The stepwise strategy of microrobotic transporter fabrication and (ii) illustration of fine-tuned biochemical, biophysical, and cell-to-cell interactions between cells and their niche [21]. (All images are used with permission). DEP, dielectrophoretic.