Measuring low electrical currents with high precision is critical across various fields, particularly in applications like microfluidic biosensing. Traditional digital multimeters (DMMs) are inadequate for low current measurements due to their high input burden and limited resolution. Therefore, more sensitive instruments like electrometers and picoammeters are often required but are typically expensive. This thesis explores the design and construction of a cost-effective, portable, and user-friendly picoammeter based on a transimpedance amplifier (TIA), capable of measuring currents in the picoampere (pA) range with a resolution of 1-5 pA and minimal noise. The constructed picoammeter has a maximum input current range of ±1.5 nA.  A prototype was built on a soldering board to validate the design, which was then translated into a practical printed circuit board (PCB) layout. The device is powered by batteries to ensure low noise levels and enable isolated operation. An Arduino microcontroller was used to interface with the circuit, manage data acquisition, and enable real-time visualisation of the measured current data on a computer.  Simulation results confirmed the theoretical performance of the circuit, and experimental validation showed RMS noise levels of less than 0.3 pA under controlled conditions and up to 3 pA when measuring streaming currents from a microchip. Despite a slight underestimation of input currents due to resistor tolerances, calibration adjustments successfully corrected these discrepancies.  The total cost of the materials used in constructing the picoammeter was significantly less than the cost of commercially available devices. While commercial devices offer higher precision and additional functionalities, the developed picoammeter demonstrates how application-focused solutions can provide comparable accuracy and noise characteristics to commercial devices for a fraction of the price.