Table 1.
Comparison of common micromanipulation tools for single cellsa. (AFM, atomic force microscopy; MT, magnetic tweezers; DEP, dielectrophoresis; OT, optical tweezers.)
| tools | principle | type | length-scale probe (nm) | typical force range (pN) | stiffness (pN nm−1) | advantages | disadvantages | |
|---|---|---|---|---|---|---|---|---|
| scanning probes | AFM | a sharp tip normal to the free end of a cantilever | point; contact | 1–10 000 | 5–10 000 | 10–10 000 | active force clamp | single cell needs to adhere tightly to a surface; random attachment |
| field gradient traps | MT | electromagnetic field gradients; magnetic beads that are attached to single cell surface | global/point; non-contact | 10–10 000 | 0.05–20 | 10−6– 0.1 | constant force; angular force for out-of-plane rotation of single cell | magnetic beads to covalent or specific non-covalent attached to cells |
| DEP | high-gradient electric field; cell dielectric properties and the surrounding medium | global; non-contact | 20–100 000 | 0.01–50 | — | simple operation | heating; two-dimensional trap | |
| OT | A highly focused beam to produce optical gradient; cell refraction index | point; non-contact | 0.1–1000 | 0.1–100 | 10−6– 0.1 | non-contact force; active or passive force clamp; well-defined geometries | photodamage or thermal damage |
a
Some data are cited from Greenleaf et al. (2007).