Koohee Han

PhD, Chemical Engineering, 2018
North Carolina State University

M.S. Chemical Engineering, 2013
North Carolina State University

B.S. Chemical Engineering, 2011
University of Seoul, Seoul Korea

Curriculum Vitae

Research Focus: Field-Driven Assembly of Anisotropic Patchy Particles for Soft Microbotics

We have shown earlier how metallo-dielectric Janus/patchy spheres and microcubes, acquire complex polarization pattern in electrical and magnetic fields, leading to multidirectional interactions. We present a novel approach for assembling metallo-dielectric microcubes into soft robotic components, which may find applications in fields such as microscale manufacturing and active microfluidics. Their potential is illustrated in a preliminary way by making motile, reconfigurable and self-folding chains from patchy microcubes, which possess repeated bending motions when actuated by an external magnetic field. The residual polarization of the metal-coated facets leads to directional forces between the neighboring particles and between the particles and the field. The dipole-dipole and field-dipole interactions lead to dynamic reconfiguration. Depending on the cube-to-cube binding conformations the assembled chains have distinct responses to the external field. In the case of cis-conformation, the junction between two cubes can be actuated reversibly by a pulsating magnetic field, whereas in the trans-conformation cube-to-cube overlap makes the junction rigid and thus restricts the bending of the chain. Consequently, the sequence of cis- and trans conformations in the chain determines how the chain will respond and fold in a field and after it is turned off. We also seek to establish fundamental understanding and identify means of control of the chain dynamics. On this basis we design and demonstrate a microbot prototype capable of grabbing and transporting target objects.

Figure 1: Capture and transportation of a cell by a microbot prototype.


Han, K.; Shields, C.W., IV; Diwakar, N.M.; Bharti, B.; López, G.P.; Velev, O.D. Sequence-encoded colloidal origami and microbot assemblies from patchy magnetic cubes. Science Advances 2017. DOI: 10.1126/sciadv.1701108.

Bharti, B.; Rutkowski, D.; Han, K.; Kumar, A.U.; Hall, C.K.; Velev, O.D. Capillary Bridging as a Tool for Assembling Discrete Clusters of Patchy Particles. Journal of the American Chemical Society 2016138 (45), 14948-14953.

News Reports

C&E News (ACS) – “Magnetic fields cause microcubes to respond like mini robots”

EurekAlert! (AAAS)“Microbot origami can capture, transport single cells”

NC State Press release – “Microbot origami can capture, transport single cells”

WIRED – “Watch a micro ‘Pac-man’ capture a live cell”

TechCrunch – “These tiny modular ‘microbots’ can change shape to capture single cells”

Phys.org –“Microbot origami can capture, transport single cells”

ScienceDaily – “Microbot origami can capture, transport single cells”