This README.txt file was generated on 20190128 by Mats Forssell ------------------- GENERAL INFORMATION ------------------- 1. Title of Dataset: Insulation impedance measurements of parylene thin-films with ceramics and silicon chips in PBS First Author Contact Information Name: Mats Forssell Institution: Carnegie Mellon University Address: Email: mforssel@andrew.cmu.edu mats.forssell@gmail.com Author Contact Information Name: Gary Fedder Institution: Carnegie Mellon University Address: Email: fedder@cmu.edu --------------------- DATA & FILE OVERVIEW --------------------- This dataset contains the measurement data for the work described in the following PhD dissertation: Mats Forssell, "Long-term insulation of active electronics embedded in compliant neural probes", PhD dissertation, Electrical and Computer Engineering, Carnegie Mellon University, 2019 In addition to this README file, the dataset contains: A. The experimental data comprise electrochemical impedance spectroscopy measurements of parylene insulation structures. Several modifications to the samples and experimental conditions are performed, grouped in different folders. Some folders include several different experimental conditions and samples. An individual description for each folder is given in the DATA ORGANIZATION section of this file. B. A TEMP folder groups temperature measurements performed for samples measured above room temperature. C. A MATLAB folder containing data processing scripts written in MATLAB which can be used to analyze the data. ----------------- DATA ORGANIZATION ----------------- Experiments are grouped in folders named "yyyymmdd_" followed by a shorthand description of the experiment in question, where the time stamp denotes the first date of the measurement for the experiment in question. Details of the files included in the experiment folders are described in the DATA DESCRIPTION section of this file. A description of each of the experiments follows: Each sample is denoted by the following code: X-y@wn v.Q, where: X indicates the insulator structure used (P for parylene, A for alumina, T for titania, N for nanolaminate) y indicates the modifications to the structure (n for no modification, a for A174, i for ion milling, f for fluorination, 4 to 4.5um thick parylene) n indicates the wafer number (samples with the same n were fabricated on the same wafer) Q indicates the design version of the samples (A,B,C,D,E1,E2,I1,I2,I3,I4) A. 20150511_old_version_interface_modifications Parylene (P) and Parylene-alumina (PA) samples with interfacial modifications. versions E1 and E2 s1: P-i@w1 v.E1 - Ion milling s2: PA-i@w1 v.E2 - Ion milling s3: P-f@w2 v.E2 - Fluorination s4: P-f@w2 v.E2 - Fluorination #this sample did not undergo the post-processing annealing like other samples s5: P-a@w3 v.E1 - A174 silanization s6: PA-a@w3 v.E2 - A174 silanization s7: P-a@w3 v.E1 - A174 silanization, on a vibration table (see setup file) s8: PA-a@w3 v.E2 - A174 silanization, on a vibration table (see setup file) B. 20150817_P Parylene (P) samples with and without A174 interfacial modification; samples measured over 6 months - version A s1: P-n@w4 v.A - no modification s2: P-n@w4 v.A - no modification s3: P-n@w4 v.A - no modification s4: P-a@w5 v.A - A174 silanization s5: P-a@w5 v.A - A174 silanization s6: P-a@w5 v.A - A174 silanization C. 20150817_PA Parylene-alumina (PA) samples with and without A174 interfacial modification; samples measured over 6 months - version A s7: PA-n@w6 v.A - no modification s8: PA-n@w6 v.A - no modification s9: PA-n@w6 v.A - no modification s10: PA-a@w7 v.A - A174 silanization s11: PA-a@w7 v.A - A174 silanization s12: PA-a@w7 v.A - A174 silanization D. 20150901_A Alumina (A) without parylene, measured at room temperature - version A s1: A@w8 v.A at 25C E. 20150901_A_temp60C Alumina (A) without parylene, measured at 60C - version A s1: A@w8 v.A at 60C F. 20150907_P_temp60C Parylene (P) samples with and without A174 interfacial modification measured at 60C - version A s1: P-n@w4 v.A - no modification # this sample is not aligned correctly in the multiplexer, see setup file for details s2: P-n@w5 v.A - A174 silanization G. 20150907_PA_temp60C Parylene-alumina (PA) samples with and without A174 interfacial modification measured at 60C - version A s1: PA-n@w6 v.A - no modification s2: PA-a@w7 v.A - A174 silanization H. 20150923_T Titania (T) without parylene, measured at room temperature - version A s1: T@w9 v.A at 25C I. 20150923_T_temp60C Titania (T) without parylene, measured at 60C - version A s1: T@w9 v.A at 60C J. 20151007_N Nanolaminate (N) without parylene, measured at room temperature - version A s1: N@w10 v.A at 25C s2: N@w10 v.A at 25C K. 20151007_N_temp60C Nanolaminate (N) without parylene, measured at 60C - version A s1: N@w10 v.A at 60C s2: N@w10 v.A at 60C L. 20151022_PN Parylene-nanlominate (PN), measured at room temperature; samples measured over 6 months - version A s1: PN@w11 v.A at 25C s2: PN@w11 v.A at 25C s3: PN@w11 v.A at 25C M. 20151022_PN_temp60C Parylene-nanlominate (PN), measured at 60C - version A s1: PN@w11 v.A at 60C s2: PN@w11 v.A at 60C s3: PN@w11 v.A at 60C N. 20151117_P_temp60C_short Parylene (P) sample with A174 modification measured at 60C for short time - version A s1: P-a@w5 v.A O. 20160403_PNT_temp60C Parylene-nanlominate/titania (PNT) measured at 60C - versions B,C,D s1: PNT-n@w12 v.B s2: PNT-n@w12 v.C s3: PNT-n@w12 v.D P. 20160406_PNT Parylene-nanlominate/titania (PNT); samples measured over 6 months - versions B,C,D s1: PNT-n@w12 v.D s2: PNT-n@w12 v.B s3: PNT-n@w12 v.C s4: PNT-n@w12 v.B s5: PNT-n@w12 v.B s6: PNT-n@w12 v.C s7: PNT-n@w12 v.C Q. 20160629_P_voltage Parylene (P) samples with applied sinusoidal voltage - versions B,C s1: P-n@w13 v.C s2: P-n@w13 v.B s3: P-n@w13 v.B s4: P-n@w13 v.B s5: P-n@w14 v.C s6: P-n@w18 v.C s7: P-n@w14 v.B s8: P-n@w14 v.B s9: P-n@w18 v.B s10: P-n@w18 v.C R. 20160629_PNT_voltage Parylene-nanlominate/titania (PNT) samples with applied sinusoidal voltage - version B s1: PNT-n@w12 v.B s2: PNT-n@w12 v.B s3: PNT-n@w12 v.B S. 20160809_PNT_temp37C Parylene-nanlominate/titania (PNT) samples measured at 37C - versions B,C s1: PNT-n@w12 v.C s2: PNT-n@w12 v.B T. 20160823_P_temp37C Parylene (P) measured at 37C - version A s1: P-n@w4 v.A s2: P-n@w15 v.A s3: P-a@w5 v.A s4: P-a@w5 v.A U. 20161013_P_thick Parylene (P) with regular and thicker samples - versions B,C s1: P-4@w17 v.C - 4.5µm thick parylene layers s2: P-4@w17 v.B - 4.5µm thick parylene layers V. 20161026_P Parylene (P) - versions B,C s1: P-n@w18 v.C s2: P-n@w18 v.C s3: P-n@w18 v.B s4: P-n@w18 v.B (sample scratched during fabrication) W. 20161122_released probe Measurements of a released probe. This is not a test structure as all the other samples. This sample has 10 channels with 15µmx115µm Pt electrodes along its length. Each of the channels 3 to 11 are connected to a different electrode. channels 2 and 12 are connected to the same electrode in a loop configuration to allow debugging. Channels 1 and 13 are connected in a loop without any electrode (this loop is a fully insulated channel following the outer edge of the probe) X. 20180123_chip_voltage Samples on glass with integrated silicon chips (Px thickness 4.5µm). Occasional voltage was applied to some samples s1: P-n@w20 v.I2 s2: P-n@w19 v.I1 s3: P-n@w21 v.I3 s4: P-n@w20 v.I2 s5: P-a@w21 v.I3 s6: P-a@w19 v.I1 Y. 20180208_chip_PNT Samples with NL/TiO2 on Si with integrated silicon chips (Px thickness 4.5µm). Occasional voltage was applied to sample 1 s1: PNT-n@w22 v.I3 s2: PNT-n@w24 v.I4 Z. 20180208_chip_voltage Samples on glass with integrated silicon chips (Px thickness 4.5µm), with 3Vpp voltage applied between FRA measurements s1: P-n@w20 v.I2 AA. 20180423_chip Samples on glass with integrated silicon chips (Px thickness 4.5µm) s1: P-n@w23 v.I4 s2: P-n@w23 v.I4 AB. 20180521_chip_released Sample with integrated silicon chips, released by grinding (Px thickness 4.5µm) s1: P-n@w25 v.I4 ---------------- DATA DESCRIPTION ---------------- Each of the experimental folders contains: 1. A setup file named "setup.txt" prepended by the folder name describing the experiment. The first lines of the file describe the samples used. Afterwards the file contains timestamped entries following "yyyymmddThhmm: " indicating a change in the experiment setup or conditions. A measurement session is usually indicated by "FRA xxmV" (xx indicates the amplitude of the excitation sinewave, in mV), with surrounding lines usually indicating the sample/position mapping (also specified in the mapping file). Abbreviations used: s1,s2,s3,...: sample 1, sample 2, sample 3,... MUX1, MUX2, MUX3,...(or PM1, PM2, PM3...): Multiplexer 1, multiplexer 2, multiplexer 3: indicates the sample position during measurement PBS: phosphate buffered saline, the electrolyte used for these measurements SB@xxC: sandbath set to the specified temperature xx (in Celsius) DIO: digital input/output (usually associated with a letter A/B/C): 8-bit digital channels from the instrument connecting to the multiplexers used to switch between sample/channel. DIO_A controls the switching between channels on one sample, while DIO_B and DIO_C control the switching between samples Vstim: applied voltage in the conditions specified (usually sinewave at 0.1 Hz and 1Vpp) 2. A mapping file "map.txt" prepended by the folder name specifying the mapping between the position of the sample during the measurement (indicated in the second column of each of the data files) and the sample number as indicated above (and in the third column of each data file). The file is ordered by columns: The first column identifies the data file being mapped (denoted by its timestamp "yyyymmddThhmm"). Each subsequent column corresponds to one of the samples being measured. The number indicates which position the sample was in. 0 is used to denote that the sample is not measured in the data file in question. -1 is used to denote that the sample has not yet been inserted in PBS during the data file in question. The ordering of the samples in columns corresponds to the sample order given in the setup file (sample 1 or s1 is in the second column, sample 2 or s2 in the third, etc...). On the first row a header gives a shorthand to the sample type being measured. The mapping information is also given in the setup file. 3. (OPTIONAL) A temperature file "temp.txt" prepended by the folder name indicating the target temperatures that the samples were placed in outside of the measurement periods. The file is ordered by columns in the same way than the mapping file: The first column indicates a timestamp at which some of the samples storage temperature is changed. The subsequent columns indicate the new temperature (in Celsius) at which the samples are kept. Typically the temperature is changed back to room temperature immediately prior to the start of a measurement session, and replaced in the higher temperature storage immediately after the end of the measurement session. All the storage temperature changes are also described in the setup file. The measured temperatures are indicated in CSV files in the TEMP folder. 4. A series of measurement data files, "yyyymmddThhmm_FRA.txt". The timestamp corresponds to the beginning of the measurement. These files are exported automatically from the Metrohm Nova software (see Methodology). The data is arranged by columns as described below: Col. 1: Repetition Col. 2: Measurement position of the sample Col. 3: Sample number Col. 4: Measured channel Col. 5: Time since beginning of experiment (t, in s) Col. 6: Frequency of measurement (F, in Hz) Col. 7: Measured impedance magnitude (|Z|, in Ohm) Col. 8: Opposite* of measured impedance phase (-phi, in degree) Col. 9: Real part of impedance (Re(Z), in Ohm) Col. 10: Opposite* of imaginary part of impedance (-Im(Z), in Ohm) *The complex impedance values usually reported by electrochemical instruments are usually Re(Z)-jIm(Z); the Autolab software follows this convention, therefore the saved files report negative phase (in col. 7) and negative imaginary impedance (in col. 9). The impedance spectra are usually measured between 100 kHz and 0.1 Hz (with 5 points per decade measured, resulting in 31 points for one spectrum). The full spectrum of one sample/channel combination is measured at a time (identical numbers in the first 3 columns for 31 consecutive rows). Once all the channels being measured have been measured on all the samples, the repetition number (col. 1) is incremented and the measurements are performed again. The sample position (col. 2) corresponds to the location of the measured sample with respect to the instrumentation. The actual sample being measured in the indicated position varies from file to file, as indicated in the setup and mapping documents. Occasional measurement errors required performing corrections to the files. When the source of error was identified, it is indicated in the setup file. The original file is kept, named "yyyymmddThhss_FRA_err.txt", and the corrected file for that measurement is named "yyyymmddThhss_corr_FRA.txt". If no correction is possible but the data cannot be used the "_err.txt" is added to the file. Occasionally, the FRA measurement is performed again after voltammetry. The second measurement is denoted by "_FRA_post.txt" 5. (OPTIONAL) A measured OCP file, "yyyymmddThhmm_OCP.txt". For measurements performed with a bias voltage different than 0 V, the open-circuit potential (OCP) is recorded and used in the FRA. The OCP file is organized by columns with: Col. 1: Repetition Col. 2: Measurement position of the sample Col. 3: Sample number Col. 4: Measured channel Col. 5: Measured open circuit potential (V) 6. (OPTIONAL) Current measurement file, "yyyymmddThhmm_Imeas.txt". Occasional voltammetry is performed on some samples. The measurement file is organized by columns with: Col. 1: Repetition - if this column is empty, the value for the line is the same as that of the line above Col. 2: Measurement position of the sample - if this column is empty, the value for the line is the same as that of the line above Col. 3: Measured channel - if this column is empty, the value for the line is the same as that of the line above Col. 4: Time since the beginning of experiment (t, in s) Col. 5: Measured voltage (in V) Col. 6: Measured current (in A) Col. 7: Applied potential (in V, should be close to Col. 5) ------------------ DATA ANALYSIS CODE ------------------ The MATLAB folder contains scripts that can be used to visualized the measured data. Plots of impedance vs time at different frequencies as well as Bode impedance plots can be generated for the different samples and channels. In order to run the code, the 'FRA_import' function must be called: it takes as argument a string corresponding to the path of the data folder to be loaded, and returns a structure containing the loaded data. Calling the FRAana function with this output structure as an argument loads a user interface for the visualization of the data. For example, the code required to display the data found in the directory '20150511_old_version_interface_modifications' is : FRAana(FRA_import('../20150511_old_version_interface_modifications')) -------------------------- METHODOLOGICAL INFORMATION -------------------------- Measurement data acquired using PGSTAT301N, Autolab Metrohm AG, Herisau, Switzerland (FW version, checked on 20181203: 3.1.5504.22201 ), with FRA module and MUX module (FRA calibration on 20181203: C1=1.68e-11 F, C2=2.46e-13 F) Data acquisition software: Autolab Nova v.1.10 to v.1.11.1. (update to v.1.11 performed on 20150218), from Metrohm AG Increased temperature samples were placed in a sandbath (VWR Analog Dry Block Heater (VWR catalog nr.: 12621-112) with sand bath module (9.5 x 22.4 x 6.4 cm, VWR Catalog Nr.: 13259-266)). The temperature is monitored using a probe: Go!Temp, Vernier Software & Technology placed in a separate PBS vial in the sandbath Temperature measurement software: Logger Lite v.1.8 (updated 20150302), from Vernier Software & Technology. Temperature measured once per minute Applied voltage outside of the measurement period is applied using an arbitrary waveform generator: Agilent 33120A Matlab code (*.m) generated and tested using v.9.2.0.556344 (R2017a) Additional information on the experiment context, methodology, and interpretation can be found in the following dissertation: Mats Forssell, "Long-term insulation of active electronics embedded in compliant neural probes", PhD dissertation, Electrical and Computer Engineering, Carnegie Mellon University, 2019