# Scaling Effects on Single‐Cell Manipulation Using Magnetic Forces at Edge of Flat Plate With Elliptically Micro‐Projection

## TL;DR

This paper explores how magnetic forces can manipulate single cells at the edge of a microfabricated plate, offering a less invasive method for cellular analysis.

## Contribution

The study introduces a novel method for single-cell manipulation at the edge of a microfabricated plate using magnetic forces and surface tension effects.

## Key findings

- The shape and scale of the projection significantly affect cell motion due to surface tension and magnetic forces.
- Design guidelines for the projection were derived based on energy minimization between interfaces.
- Accurate single-cell manipulation was demonstrated on microfabricated plates with different projection shapes.

## Abstract

Single‐cell manipulation is needed for various cellular analyses and biomedical applications. In the conventional single‐cell manipulation methodology, cells are the center of a flat dish or hollow space, where the medium spontaneously penetrates. However, manipulation at the edge of the plate, where the flow of the medium is interrupted by its surface tension, has not yet been shown. In this study, we manipulated single cells labeled with magnetic nanoparticles at the edge of a projecting microfabricated plate under a magnetic field, which offer a less invasive method for cellular analyses, not limited by the shape of the culture devices. As a cell is affected by both the surface tension of the medium and magnetic force, we investigated the effects of the shape and scale of the projection on cell motion. Owing to energy minimization between the liquid–air and solid–liquid interfaces determined by the structure of the projection, the area of solution spreading in the projection converged, and we obtained design guidelines for the projection that enabled cell manipulation. Demonstrating accuracy in single‐cell manipulation on a microfabricated flat plate with different projection shapes contributes to developing single‐cell analyses, including applications such as single‐cell‐based polymerase chain reactions.

To develop the single‐cell manipulation on the flat plate, cells labeled with magnetic nanoparticles were manipulated using magnetic force for less invasive cellular analyses at the edge of a projecting microfabricated plate. The optimal shape and scale of the projection was investigated considering the effects of the flow in the droplet on the plate and magnetic field distribution.