A low-cost and high-precision scanning electrochemical microscope built with open source tools

Abstract

12A low-cost Scanning Electrochemical Microscope (SECM) was built with a 0.6 pA current 13 measurement capability potentiostat and submicron resolution motorized stage, using open source 14 software and hardware tools. The high performance potentiostat with a Python graphical user 15 interface was built based on an open source project. Arduino boards, stepper motors, a manual XY 16 micromanipulator stage, 3D printed couplers and gears were used in building the motorized stage.17An open source motor control software was used for moving the motorized stage with high 18 precision. An inverted microscope was utilized for viewing a standard microelectrode while 19 scanning. The setup was tested in the formation of a map of electrochemical signals from an array 20 of pores on a parafilm membrane. As the setup will be used in future biosensing experiments, DNA 21 hybridization detection experiments were also performed with the setup. 22 23 2 24 104 3D printed parts and gears, where the difference in size and teeth numbers between gears enabled 105 reduction of motor speed and hence the step size of the stage motion. The gear ratio was N Large-106 50 /N Small-13 = 3.84, providing about 4 times reduction on the angular speed of each axis according 107 to w L N L =w s N s . The stepper motors were controlled with the Arduino board in conjunction with 108 Easy Driver v4.4 shields, which resulted in further reduction of motor speeds by enabling 109 adjustments to the supplied currents to the stepper motors. The reduction of the stepper motor 6 110 speed through gears and current control enabled stepwise motion of an axis by 500 nm in each 111step. This was demonstrated in the S1_Video as a supplementary information, where the tip of a 112 tapered tungsten wire, that is attached to the motorized stage, covers the 10 micron distance 113 between two lines on a calibration slide in 20 steps. 114The stepper motor controller electronics including the Arduino board was housed in a 115 custom 3D printed box. A custom Arduino shield was built using a perfboard to hold the two Easy 116 Driver shields, the output power jacks for stepper motors and the DC power input jack, where a 117 9.75V DC adapter was utilized to power stepper drivers. A 5V fan was also installed in the box to 118 cool down the Easy Driver shields during operation. The open source GRBL software with a 119 graphical user interface was utilized in sending commands to the stage for stepwise motorized scan 120 of a preferred area [17]. This software is also capable of automatically moving the XY stage 121 according to a user uploaded image pattern and an example is presented as a supplementary 122 information movie (S2_Video). GRBL software's website provides detailed instructions for 123 establishing communication between the software and the Arduino board [17]. A detailed parts 124 list, 3D printable part files, GRBL software operation instructions, and a summary cost break down 125for the motorized stage are provided as supplementary information. We have also demo...