**3. Dielectrophoresis**

been extensively studied in micro-/nanofluidic system integrated with active manipulation mech-

Micro-/nanofluidic system facilitates researchers in creating well-controlled micro-/nanoscale environment and at the same time enables the analysis of micro-/nanoparticles including biological particle (bioparticle) behaviors and responses toward active manipulation mechanisms, in addition to particle-particle reactions and external stimuli [5]. Active manipulation mechanisms make possible the control of bioparticle displacement and motional trajectories in a highly predictable and consistent fashion [2], by introducing tunable external force systems such as dielectrophoresis (DEP) [6, 7], magnetophoresis (MAG) [8], acoustophoresis (ACT) [9], thermophoresis (THM) [10], and/or optical tweezing/trapping (OPT) [11, 12].

In this chapter, description of the fundamental mechanism underlying the phenomenon is presented, covering the theoretical and schematic description, as well as specific implementation into bioparticle manipulation covering from micron-sized material down to molecularlevel particles. Conclusion and future perspectives of this multidisciplinary field are provided

Manipulation of bioparticles has been a major concern in recent development of micro−/nanofluidic studies due to their potential in biomedical application. Those particles, according to their biological structure and physical properties, can be categorized as (1) model organisms; (2) body cells, which include blood cells, tumor and cancer cells, and stem or progenitor cells;

Model organisms, either unicellular (e.g., yeast) or multicellular (e.g., *Danio rerio* zebrafish, *Caenorhabditis elegans* nematode, etc.), are being used for cellular process studies (cell cycle, cell division, metabolism, etc.), genetic and pharmacological studies, as well as pathogenesis and therapy studies. Blood which composed by two components, i.e., (1) blood plasma and (2) the formed elements, including red blood cells (RBCs), white blood cells (WBCs), and platelets, is of high interest as they are being used in various health check and clinical tests, such as blood test to determine whether our organs (e.g., kidneys, liver, thyroid, heart, etc.) are working properly and to diagnose any disease such as HIV/AIDS, cancer, anemia, diabetes, and coronary heart disease. Tumor cells (benign) and cancer cells (malignant) are cells that undergo uncontrolled proliferation, causing tumor development either at the skin, colon, rectum, prostate, breasts, or lungs. They are grouped either as (1) carcinomas (develop in epithelial cells), (2) leukemia and lymphomas (develop at the blood and lymphatic system), or (3) sarcomas (develop at the connective tissue). These cells attempt to develop secondary tumor (metastasis tumor) by spreading through vascular or blood vessel network in the form of circulating tumor cells (CTCs). Stem cells, either adult stem cells or pluripotent stem cells, are cells that can self-renew, generating perfect copies of themselves by division and differentiation, where the produced cells are specific for certain function in the body. These cells are important in research, drug screening test, and cell transplantation therapy. Bacteria, which are unicellular

anisms [2–4].

84 Microfluidics and Nanofluidics

at the end of this chapter.

**2. Bioparticles in biomedical studies**

(3) bacteria; (4) viruses; (5) nucleic acids; and (6) proteins.

Dielectrophoresis (DEP) is the motion of polarizable particles under a spatially nonuniform electric field that cause momentary polarization of the particle by dipole establishment within, with an unequal Columbic forces at both ends of the particles, causing the particles to move [2, 6, 7].
