  Citation: Khan, M.S.; Mei, S.; Shabnam; Ali Shah, N.; Chung, J.D.; Khan, A.; Shah, S.A. Steady Squeezing Flow of Magnetohydrodynamics Hybrid Nanofluid Flow Comprising Carbon Nanotube-Ferrous Oxide/Water with Suction/Injection Effect. Nanomaterials 2022, 12, 660. https:// doi.org/10.3390/nano12040660 Academic Editors: Simone Morais and Konstantinos Spyrou Received: 23 December 2021 Accepted: 8 February 2022 Published: 16 February 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). nanomaterials Article Steady Squeezing Flow of Magnetohydrodynamics Hybrid Nanofluid Flow Comprising Carbon Nanotube-Ferrous Oxide/Water with Suction/Injection Effect Muhammad Sohail Khan 1 , Sun Mei 1, *, Shabnam 1 , Nehad Ali Shah 2 , Jae Dong Chung 2 , Aamir Khan 3, * and Said Anwar Shah 4 1 School of Mathematical Sciences, Jiangsu University, Zhenjiang 212013, China; sohailkhan8688@gmail.com (M.S.K.); shabnam8688@gmail.com (S.) 2 Department of Mechanical Engineering, Sejong University, Seoul 05006, Korea; nehadali199@yahoo.com (N.A.S.); jdchung@sejong.ac.kr (J.D.C.) 3 Department of Mathematics and Statistics, University of Haripur, Haripur 22620, KPK, Pakistan 4 Department of Basic Sciences and Islamiat, University of Engineering and Technology Peshawar, Peshawar 25120, KPK, Pakistan; anwarshah@uetpeshawar.edu.pk * Correspondence: sunm@ujs.edu.cn (S.M.); aamir.khan@uoh.edu.pk (A.K.) Abstract: The main purpose of the current article is to scrutinize the flow of hybrid nanoliquid (ferrous oxide water and carbon nanotubes) (CNTs + Fe 3 O 4 /H 2 O) in two parallel plates under variable magnetic fields with wall suction/injection. The flow is assumed to be laminar and steady. Under a changeable magnetic field, the flow of a hybrid nanofluid containing nanoparticles Fe 3 O 4 and carbon nanotubes are investigated for mass and heat transmission enhancements. The governing equations of the proposed hybrid nanoliquid model are formulated through highly nonlinear partial differential equations (PDEs) including momentum equation, energy equation, and the magnetic field equation. The proposed model was further reduced to nonlinear ordinary differential equations (ODEs) through similarity transformation. A rigorous numerical scheme in MATLAB known as the parametric continuation method (PCM) has been used for the solution of the reduced form of the proposed method. The numerical outcomes obtained from the solution of the model such as velocity profile, temperature profile, and variable magnetic field are displayed quantitatively by various graphs and tables. In addition, the impact of various emerging parameters of the hybrid nanofluid flow is analyzed regarding flow properties such as variable magnetic field, velocity profile, temperature profile, and nanomaterials volume fraction. The influence of skin friction and Nusselt number are also observed for the flow properties. These types of hybrid nanofluids (CNTs + Fe 3 O 4 /H 2 O) are frequently used in various medical applications. For the validity of the numerical scheme, the proposed model has been solved by another numerical scheme (BVP4C) in MATLAB. Keywords: steady; hybrid nanofluid flow; variable magnetic field; parametric continuation method (PCM); BV4C Schemes 1. Introduction Heat transfer through the flow of fluid on the plate surface or on the surface of a revolving disk is gaining incredible interest from researchers due to its many uses in the aeronautical sciences and engineerings including chemical processes, thermal-energy- producing systems, geothermal industry, gas turbine rotators, medical equipment, rotating machinery, and computer storage. The squeezing flow produces by the motion of the boundaries play a significant role in polymer processing, hydrodynamical machines, lubri- cation equipment, etc. Due to its wide range of applications in many modern technologies, it can be considered a good source of heat transmission. Researchers have also updated the squeezing flow through the introduction of new ideas known as nanofluids. Nanofluids Nanomaterials 2022, 12, 660. https://doi.org/10.3390/nano12040660 https://www.mdpi.com/journal/nanomaterials