DOI: 10.5061/dryad.80gb5mkxf
title: Data from: Stretchable Arduinos embedded in soft robots

description: To achieve real-world functionality, robots must have the ability to carry
 out decision-making computations. However, soft robots stretch
 and therefore need a solution other than rigid computers.
 Examples of embedding computing capacity into soft robots currently
 include appending rigid printed circuit boards (PCBs) to the
 robot, integrating soft logic gates, and exploiting
 material responses for material-embedded computation. Although
 promising, these approaches introduce limitations such as rigidity,
 tethers, or low logic gate density. The field of stretchable electronics
 has sought to solve these challenges, but a complete pipeline for
 direct integration of single-board computers, microcontrollers, and other
 complex circuitry into soft robots has remained elusive. We present a
 generalized method to translate any complex two-layer circuit
 into a soft, stretchable form. This enabled the creation of
 stretchable single-board microcontrollers (including Arduinos)
 and other commercial circuits (including Sparkfun circuits), without
 design simplifications. As demonstrations of the method’s utility, we
 embed highly stretchable (&gt;300% strain) Arduino Pro Minis
 into the bodies of multiple soft robots. This makes use of
 otherwise inert structural material, fulfilling the promise of the
 stretchable electronics field to integrate state-of-the-art
 computational power into robust, stretchable systems during
 active use.
description: Data was collected with MATLAB, Arduino, or Instron (materials
 testing) software, and processed in MATLAB. Relevant details are below.
 Please see the paper for more information.  OGaIn fabrication and
 characterization:<br>XRD testing was completed on a
 Rigaku SmartLab machine with a 2 mm window. SEM images were taken on a
 Hitachi CFE SU8230. EDS analysis was performed with a Bruker QUANTAX
 FlatQUAD (mapping at 5 kV and compositional analysis at 6 kV). Surface
 samples were prepared on 12.5 mm stubs on carbon tape. Cross-section
 samples were prepared on vertical sample holders on carbon tape, where a
 trace of OGaIn was frozen and then broken in half and mounted to the stub.
 Stretched cross sections were prepared by casting OGaIn on VHB,
 encapsulating it with rubber cement, and then stretching the substrate
 while applying it to the SEM stub. After mounting the sample, it was
 frozen and then broken to reveal the stretched cross-section. 
 The single-trace samples were created using the dimensions and
 electrode attachment techniques described in (45), with VHB tape and
 rubber cement as the substrate and encapsulant, respectively. The trace
 widths of OGaIn were 250 μm, with gauge length 25 mm (Fig. S3B, C). 0 Ω
 resistor samples were made using the same patterns and processes, but with
 a 0.25 mm gap in the middle of the trace, over which a 0402 0 Ω surface
 mount resistor was placed (Fig. S3E). The single trace samples were
 characterized using the custom setup previously described in (45), and
 illustrated in Fig. S3D. An Arduino-driven lead-screw actuator controlled
 the strain and strain rate, as resistance was recorded using a 4-point
 probe multimeter (BK<br>Precision). Substrate viability
 characterization: ASTM D6195-22 standard
 tack testing was carried out using an Instron 3345 tensile tester (maximum
 capture rate 2 ms, Fig. S9A). Five samples of each material were created
 as follows: VHB tape was adhered to the polyethylene terephthalate (PET)
 backing, ensuring no air bubbles were present. The DS10 (DragonSkin 10A,
 SmoothOn Inc.) samples were made by casting DS10 over the PET backing with
 a 0.5 mm drawbar. That same technique was used to create the samples of
 Slackers 1, 2, and 3. Slacker 1 used one part DS10 Part B, one part
 Slacker (SmoothOn, Inc.), and one part DS10 Part A (denoted, 100:100:100).
 Slacker 1.5 used the ratio 100:150:100, and Slacker 2 used 100:200:100.
 The same setup, sample creation, and procedure were used for the OGaIn
 adhesion as for the previously described tack testing, though instead of
 coming into contact with steel, the samples came into contact with molded
 OGaIn (Fig. S9B-E). A 25 ×25 mm, 1/16 in deep mold was created to fit onto
 the steel bar used for previous experiments (Fig. S9B). This mold was
 filled with OGaIn before each new sample, and a bar was drawn across the
 top surface before the removal of the mold (Fig. S9C).
 Circuit
 characterization: The five Arduino Pro
 Mini samples used for pull-to-failure tests were manufactured with a
 border on the edges such that fabric could be adhered, limiting the strain
 in those regions and ensuring that only the circuit board was straining.
 To set up, these fabric regions were gripped (Instron 2713-007) by the
 materials testing system (Instron 3345), and the wires for serial
 connection were plugged into an FTDI (Future Technology Devices
 International Limited) programming board (Sparkfun DEV-09716), which was
 connected to a laptop. A code that flashed four off-board LEDs and printed
 timestamps to the serial monitor was uploaded to the Soft Pro Mini. The
 laptop and Arduino were recorded by an external camera setup. The Instron
 captured force and displacement data while it pulled upward at a rate of
 15 mm/min until serial disconnect occurred. The initial length and length
 at failure of the circuit were calculated from the camera footage (with
 one initial frame, and one frame just before serial disconnect), and from
 these, engineering strains were calculated. This same process was used to
 test the failure of the three additional example circuits, one sample
 each, though they were gripped with acrylic adhered to the circuit as the
 strain limiter. The Arduino Lilypad was strained until the LED stopped
 blinking at the rate specified in the script. The Sparkfun Sound Detector
 was strained with loud ambient noise to detect failure time. The Sparkfun
 RGB and Gesture Sensor sent color output through serial until an error
 reading serial occurred. For all measurements in this paper, we chose to
 calculate the strain clamp-to-clamp (field standard (17, 26–28, 36)).
 Cyclic testing of the soft Arduino Pro Minis used the same cyclic testing
 device as for the single-trace samples. The same additional grip areas
 were used, but instead of attaching fabric, laser-cut pieces of 1/8”
 acrylic were pressed onto either side of the excess VHB tape such that the
 four through holes fit onto the alignment pins of the cyclic tester (Fig.
 S11). The cyclic tester strained to 100% strain for 1000 cycles, while a
 time-lapse camera monitored the laptop screen, which concurrently
 displayed the serial output from the soft circuit, and the cycle number
 from the testing device. The number of cycles the circuit survived was
 recorded as the cycle before an error was seen in the serial output of the
 stretchable Arduino. After pull-to-failure and cyclic testing until serial
 disconnect, the samples were evaluated using the 2-point probe FLUKE
 multimeter to determine where the failure occurred (Fig. S7C). To
 determine the effect the circuitry had on the circuit substrate’s
 force-strain relationship, the same strain-limiting fabric pieces were
 attached to five stretchable Pro Mini circuits and five pieces of plain
 VHB tape. The materials testing system gripped these sections and
 strained each sample to 100% strain for 200 cycles, at 15 mm/min. Data
 from cycles 1, 10 (after Mullin’s effect (57), and 200, straining and
 relaxing, were isolated for each sample. The means and standard deviations
 were then calculated for the five samples, from cycles 1, 10, and 200,
 straining or relaxing.
description: # Stretchable Arduinos embedded in soft robots
 [https://doi.org/10.5061/dryad.80gb5mkxf](https://doi.org/10.5061/dryad.80gb5mkxf) This contains both the CSVs of data in the paper and the MATLAB files I used to process those .csv files. It also contains raw images used in some figures where data was obtained.  General: Each MATLAB script starts with the figure name it corresponds to (i.e., Fig 5c), and the script will ask for a .csv file upload. Choose the .csv with the corresponding figure name in the title. The script will output the data as plotted in the paper. The code is sectioned and commented on for easy understanding. NOTE: Fig 2D requires the 50 .csv files without a figure name in the file name to be in the same folder as the Fig 2D MATLAB script. These files do not have the Figure 2D indicator in the titles. Run the script with the 50 other files here in the same location, and you will get that plot.  In more detail:  * Fig*2A*_Compiled_400str_Samples.csv is the electromechanical data (resistance (Ohms), displacement (mm)) of the five samples needed for Fig_2A_Plotting_400str_Single_Trace_Samples.m to plot the data.  * Fig_2B_ogain_VHB_0.25_22ms_150str_1000cyc_S8.csv is the electromechanical data (resistance (Ohms), displacement (mm)) of the five samples needed for Fig_2B_Plotting_cyclic_Single_Trace_Samples.m to plot the data.  * Fig_2C_Cyclic Data 2022-09-23 09.55.36.csv is the electromechanical data (resistance (Ohms), displacement (mm)) for Fig_2C_Plotting_cyclic_Single_Trace_Samples.m to plot the data.  * Fig*2D_*tack_tests.m is paired with the below files, which plot the data: 100_1.csv through 100_5.csv contain tack testing data for Slacker 1 against steel with time (s), displacement (mm), and force (n) data. 150_1.csv through 150_5.csv contain tack testing data for Slacker 1.5 against steel with time (s), displacement (mm), and force (n) data. 200_1.csv through 200_5.csv contain tack testing data for Slacker 2 against steel with time (s), displacement (mm), and force (n) data. DS10_1.csv through DS1*0*_5.csv contain tack testing data for DS10 against steel with time (s), displacement (mm), and force (n) data. VHB_Proper_backing_1.csv through VHB_Proper_backing_5.csv contain tack testing data for Slacker 1 against steel with time (s), displacement (mm), and force (n) data. 100_ogain_1.csv through 100_ogain_5.csv contain tack testing data for Slacker 1 against ogain with time (s), displacement (mm), and force (n) data. 150_ogain_1.csv through 150_ogain_5.csv contain tack testing data for Slacker 1.5 against ogain with time (s), displacement (mm), and force (n) data. ogain_200_1.csv through ogain_200_5.csv contain tack testing data for Slacker 2 against ogain with time (s), displacement (mm) and force (n) data. DS10_ogain_1.csv through DS1*0*_ogain_5.csv contain tack testing data for DS10 against ogain with time (s), displacement (mm), and force (n) data. VHB_ogain_1.csv through VHB_ogain_5.csv contain tack testing data for Slacker 1 against ogain with time (s), displacement (mm), and force (n) data. * Fig_4D_raw_data.csv contains the tensile testing data (force (N), displacement (mm)) used to plot Fig_4D_Plotting_Pull2SCF.m. The accompanying Fig_4D[...].png files are image files used to calculate strains at failure. * Fig_4E_Plotting_Cyc2SCF.m plots the cycle to failure data results.  * Fig_4F_Force_1_10_200_2_nohead.csv is the raw tensile data (force (N), disp. (mm)) used in Fig_4F_Plotting_Cyc_Force_4_1_10_200.m to plot tensile test data.  * Fig_5[...].png files image files used to calculate strains at failure. * Fig_S1_raw_data_oGaIn.csv is the raw XRD data used in Fig_S1_XRD_plot.m to plot the XRD curve.  * Fig_S2_test_2_amp_sweep_ogain_1500um_for_MATLAB_plus_egain_trial2.csv is the rheometer data (stress, strain, etc.) used with Fig_S2_process_amp_sweep_4_plots.m to plot the rheometer data.  * Fig_S2_Test_3_flow_sweep_ogain_1500um_w_egain_trial_3.csv is the rheometer data (viscosity) used with Fig_S2_process_flow_sweep_1_plot.m to plot the rheometer data.  * Fig_S4_ogain_direct_comp_compiled.csv contains electrotechnical data (resistance (ohms), disp. (mm)) used to plot with Fig_S4_400str_direct_geometric_comparison.m. * Fig_S5_400str_compiled_0Ohm contains electrotechnical data (resistance (ohms), disp. (mm)) used to plot with Fig_S5_Plotting_400str_Single_Trace_Samples.m. * Fig_S6_transmission_line_results.m contains the data (resistance (ohms), distance (mm)) and plots it.  * Fig_S10_Compiled.csv contains the tensile data (force (N), displacement (mm)) for the compared materials, and Fig_S10_processing_tensile_data_and_modulus.m plots it.