DOI: 10.5061/dryad.9w0vt4bn7
title: Data from: Microrobots powered by concentration polarization electrophoresis

description: Second-order electrokinetic flow around colloidal particles caused by
 concentration polarization electro-osmosis (CPEO) can result in a phoretic
 motion of asymmetric particle dimers in a homogeneous AC electrical field,
 which we refer to as concentration polarization electro-phoresis (CPEP).
 To demonstrate this actuation mechanism, we created particle dimers from
 micron-sized silica spheres with sizes 1.0 µm and 2.1 µm by connecting
 them with DNA linker molecules. Systematic experiments exploring the
 dependence of the dimer migration speed on the electric field strength,
 frequency, and buffer composition align with the theoretical framework of
 CPEO. This dataset contains microscopy videos that show the migration of
 these particle dimers under varying electric field strengths, frequencies,
 and buffer compositions.
description: # Dataset supporting the article "Microrobots Powered by
 Concentration Polarization Electrophoresis (CPEP)"
 [https://doi.org/10.5061/dryad.9w0vt4bn7
 ](https://doi.org/10.5061/dryad.9w0vt4bn7) The dataset contains microscopy
 videos of migrating microrobots recorded with an Olympus IX71 microscope.
 The microscopy videos were recorded at different electric field strengths
 and frequencies, and at varying buffer concentrations. These videos form
 the basis for Figures 5 and 6 in the associated publication. Additionally,
 the dataset contains ImageJ macros for manual measurement of dimer
 migration speeds, as well as a .csv files containing the measurements
 generated with these macros. ## Description of the data and file structure
 There are two datasets. The first is provided in the folders
 "MgCl_and_NaCl.zip" and "NaOH_and_trisHCl.zip," each
 containing two folders for a different electrolyte type. The second is
 "voltage_and_freq.zip", which contains three folders, each for a
 different microrobot, tested at various frequencies and voltages. Inside
 the folders, there are microscopy videos from which we extracted the
 microrobot velocities for both the voltage-frequency plot and the analysis
 of velocities at varying salt concentrations. The filenames of the videos
 specify the experimental conditions under which we conducted the
 experiments. For instance, vpp11_250hz_0uMMgCl_50uMnaoh_2 denotes an
 experiment carried out at an amplifier voltage of 11 Vpp, a frequency of
 250 Hz, a MgCl concentration of 0 µM, and an NaOH concentration of 50 µM.
 The final digit, 2, indicates that this is the second video recorded under
 these conditions. Adjacent to the TIFF files in the directory, we provide
 metadata files that include timestamps for each recorded frame, measured
 in milliseconds. Note that the resolution information in the TIFF files is
 incorrect due to the manual insertion of the objectives. Although we
 utilized a 20x objective, the scale is saved for a 4x objective. The
 correct scale may be calculated using the corresponding fraction. The
 actual concentration of Tris is twice the value stated in the filename.
 This discrepancy arose because we recorded ionic strength rather than
 concentration. Tris was titrated to a pH of 8.4, corresponding to its pKs,
 where half of the Tris exists in its ionic form. ## Code/Software Within
 the subfolders designated for frequency and voltage plots, we have
 included two ImageJ macros. Each subfolder contains a distinct macro that
 must be installed via Plugins -&gt; Macros -&gt; Install in ImageJ to
 become usable. We employed these macros for manual measurement of the
 microswimmer velocities. For frequency and voltage measurements: * Upon
 installing the macro, the user should first select the multipoint tool. *
 In the video, the user marks both the starting and ending positions of a
 particle within the relevant frames. * Pressing 's' or
 'r' will automatically save these positions; 's' is
 used for a swimmer measurement, while 'r' designates a reference
 particle measurement. For salt measurements: * The macro offers three
 optional buttons—'u,' 'd,' and 'r.' * The
 'u' button is for a swimmer pointing upwards with the larger
 particle, 'd' for downwards, and 'r' for reference
 particles. ## Measurements We include the measurements we made with the
 macros in the corresponding folders where the raw data are stored as CSV
 files, named "Results_*.csv." For buffer measurements, the file
 is named "Results_ud.csv." Each measurement is represented by
 two successive lines in the file. * The first line indicates the start
 position of a microswimmer. * The second line represents the end position.
 The column headers are "X, Y, Slice, direction, type, title,
 dir" * The first column is simply an increasing number with no
 specific meaning. * X and Y represent the coordinates in pixels. * Slice
 refers to the frame number where the measurement was made. * Direction
 indicates whether the microswimmer points with the larger particle upwards
 or downwards. * Title is the name of the microscopy video where the
 measurement was made. * Dir specifies the directory where the video was
 located when the measurement was conducted. For frequency and voltage
 measurements, the file structure is similar, but the direction column is
 omitted, as all dimers move with the larger particle in front.