A Method for Guiding Nano and Micro Scale Objects Based on Externally Controlled Multi-Directional Environmental Gradients


This technology is a multi-directional control mechanism for wavelength-sized particles. Through an induced thermal gradient, these particles can be controlled in biological, medicinal, microfluidic, and colloidal applications.

Problem Addressed

The motion of nano- and micro-scale particles can be controlled via chemical, electric, magnetic, acoustic, and temperature effects. Wavelength-sized particles can be guided with the help of light as can be seen in optical tweezer and optical tractor beam applications. Unfortunately, the complex environments in which these particles reside cause light scattering. Thus, it is unreliable to control particles simply through light.

Luckily, a process called thermophoretic drift can guide particles through a light-induced thermal effect. Propulsion occurs along the axis of a temperature gradient that has been induced by the heat generated from light absorption in the particle. Although thermophoretic drift is robust to scattering, the process has difficulty changing the direction of particles in motion. This technology addresses this challenge adding a multi-directional component to thermophoretic drift.


This technology comprises a composite nano-particle, a monitoring system to track particles, and a method for controlling the motion of particles. The composite particle consists of a main body and two sides. The main body is a polystyrene particle and the two sides are made of gold and titanium nitride. The monitoring system takes real-time video of the particle’s motion, analyzing direction and distance to the particle’s target location.

The motion control method for this technology is based around an induced thermal gradient in the composite nano-particle. A light source with a constant wavelength illuminates the composite nano-particles and causes a thermophoretic drift along the direction from one side of the particle to the other. Additional thermophoretic effects can be created along the particle by shining more lights with different wavelengths at the particle. Asymmetric absorption of light at different wavelengths results in a tunable system for multi-directional propulsion of the composite nano-particles.


  • Multi-directional control of nano- and micro-particles through the thermophoretic effect
  • Increase in time efficiency through faster guidance speeds
  • Robust to scattering of light