Optical tweezers are scientific instruments that use a highly tightly focused laser beam to hold and move microscopic and sub-microscopic objects like atoms, nanoparticles and droplets. They can manipulate nanometer and micron-sized particles by exerting extremely small forces (piconewton’s) via a highly focused laser beam. Optical tweezers are used in biology and medicine, for example, to grab and hold a single bacterium, a blood cell, or a molecule like DNA, proteins, and molecular motors.

NaYF4: Er, Yb upconverting particles refer to microcrystalline particles that exhibit upconversion luminescence emission (UCPs). Upconversion luminescence is a phenomenon where a material absorbs multiple low-energy photons and emits a higher-energy photon. UCPs have various applications, including bioimaging, biosensing, and photodynamic therapy. We trap a single hexagonal-shaped upconverting particle on the absorption resonance pump wavelength at 975 nm with linearly polarized laser light. We have developed a new technique for producing yaw rotational motion and axial Brownian motion of the upconverting particles in optical tweezers. In this technique, we place a polarizer orthogonal to the input polarization in the backscattered direction and find that the spectra vary upon the orientation of the polarizer with respect to the side axis of the particle. We use this to ascertain the rotational Brownian motion in the yaw sense. We also use the visible emission from the UCPs to ascertain the axial Brownian motion of the particle by using a correctly sized aperture along the path of the backscatter direction.

Poly (3,4-ethylene dioxythiophene): Poly (styrene sulfonate) is abbreviated as PEDOT: PSS is the most suitable conductive polymer material. A continuous solid pattern of the PEDOT: PSS conductive polymer has been deposited on glass substrates by thermo-optical tweezers. However, the width of the pattern deposited is limited by the size of the microbubble formed, which is typically comparable to the diffraction-limited spot size, given that the infrared light is focused through a high Numerical Aperture (N.A.) lens. We subsequently cut to the desired width by using high-intensity femtosecond pulses. The solution works well till a thickness of about 1