Atomic Force Microscopy (AFM) is one member in the Scanning Probe Microscopy family which has powerful applications in various materials, especially in the biological field. Even though AFM can scan samples in high resolution in air media, it still has some contaminations such as dirt, temperature parameters, and noise, etc., which affect the resolution. Reasonably, researchers have constantly come up with advancements in AFM with many methods - one of the promising methods is scanning in liquid. However, conventional liquid scanning uses chemical coated glass substrates, which has drawbacks such as the evaporation of the liquid if the specimen needs to be effectively observed for a long period of time. Developments in the fluid cell are being done to overcome such drawback. Furthermore, using a fluid cell can change the solution used in experiments without restarting the calibration of the AFM mode again. This work combined the functions of 3D printers, AFM, and finite element analysis software to develop a 3D printed AFM fluid cell for AFM measurements in liquid to investigate the mechanism of chemicals on the bio-sample structure, especially disease-causing its capability to bacteria. Several designs of the 3D printed AFM fluid cell were developed using Solidworks and ANSYS software; and it was produced using a commercial 3D printer. This fluid cell has been successfully tested on biological samples by liquid-phase continuous scanning for bacteria such as Streptococcus mutans and Staphylococcus aureus. Staphylococcus aureus and Streptococcus mutans are classified as a Gram-positive bacterium. While Staphylococcus aureus causes a prevalent human pathogen via broken skin or mucous membranes, such as nosocomial infection of surgical wounds, etc; Streptococcus mutans causes decay in the human oral cavity which can lead to heart valve isolation. In this study, citric acid was chosen to study its effects on the bacteria as citric acid is readily available and used in human daily life. Using AFM in liquid combined 3D printed AFM fluid cell, the adhesion, dissipation and deformation of the bacteria in the pH range of citric acid solution were carefully studied, as pH increases, the adhesion and dissipation decrease while deformation increases. Thus, there are two hypotheses discussed; if the bacteria become harder at lower pH and the different time cycles of adhesion, deformation, dissipation and modulus graphs are related to the Krebs cycle time. Furthermore, according to the ANSYS simulation and AFM experimental results, the 3D printed AFM fluid cell proved to be valuable in bio-medical experiments.

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