Arabian Journal for Science and Engineering https://doi.org/10.1007/s13369-020-04467-w RESEARCH ARTICLE-MECHANICAL ENGINEERING Investigation of Physico-mechanical Behavior, Permeability and Wall Shear Stress of Porous HA/PMMA Composite Bone Scaffold Babar Pasha Mahammod 1 · Emon Barua 1 · Payel Deb 1 · Ashish B. Deoghare 1 · Krishna Murari Pandey 1 Received: 4 August 2019 / Accepted: 23 December 2019 © King Fahd University of Petroleum & Minerals 2020 Abstract Hydroxyapatite (HA)-based composite bone scaffolds are developed using solvent casting particulate leaching technique by varying the weight percentages of HA from 50 to 70% (w/w) in polymethyl methacrylate matrix. The chemical properties of the developed scaffolds are investigated by XRD analysis which shows the presence of crystalline HA and traces of β-TCP in the scaffolds. The microstructure of the scaffolds is studied by the SEM micrographs, which show porous morphology with an average pore size of 119 ± 18–148 ± 23 μm and a maximum pore size of 148 ± 23 μm for HA 50 scaffold. The highest porosity of 75 ± 2.0% is recorded for HA 50 scaffold by conducting liquid displacement test and a maximum compressive strength of 6.26 ± 0.53 MPa is recorded for HA 60 scaffold by performing uniaxial compression test of the scaffolds. The permeability and wall shear stress (WSS) of the scaffolds are investigated by computational fluid dynamics (CFD). The CFD analysis is performed in a fluid domain developed by Boolean operations on the CAD model of the scaffold developed using micro-computed tomography-based 3D image acquisition technique by Mimics V1. Results show that the permeability increases and WSS decreases with an increase in the porosity of the scaffolds. However, both permeability and WSS obtained for the developed scaffolds are within the limit prescribed for the growth of bone tissues. It is concluded that scaffolds with 60 wt% of HA exhibit the best combination of porosity, permeability and compressive strength making it suitable for bone tissue engineering applications. Keywords Compressive strength · Porosity · Permeability · Wall shear stress · 3D image analysis 1 Introduction Bone has the capability to regenerate itself and compensate for any bone loss caused by defects. But the regeneration capacity is limited to small defects. Larger defects, known as segmental bone defects (SBDs), cannot be self-healed [1]. Because of this reason, bone is the second most transplanted tissue after blood [2]. The present approaches for the treat- ment of SBDs include autografts and allografts. However, these techniques have been reported with various limitations which encouraged the use of bone tissue engineering (BTE) [2, 3]. The aim of BTE is to repair or reconstruct/regenerate bone defects by combining cells, scaffolds and appropriate signaling factors [4, 5]. The key challenge in BTE is to fab- ricate a scaffold that can mimic the host bone structure in B Emon Barua imon18enator@gmail.com 1 Department of Mechanical Engineering, National Institute of Technology Silchar, Silchar, Assam 788010, India terms of porosity, compressive strength, permeability and wall shear stress [6]. Porosity percentage is defined as a fraction of void volume over the total volume of the scaffold. Scaffolds with requisite porosity enable better cell seeding and migration of the cells, leading to tissue regeneration [7, 8]. Along with the porosity, the pore size of the scaffold also has a significant role. A larger pore size decreases the internal surface area to volume ratio, which provides more room for better cell attachment, tissue in-growth and vascularization [9]. In order to act as a suitable framework for tissue growth, a scaffold should have a porosity between 60 and 90% [10] with an average pore size of 100–400 μm[3, 11]. Compressive strength of the scaffolds enables the load- bearing capability which supports the tissue growth. The compressive strength of a scaffold is expected to be close to the native bone to be repaired with a minimum prescribed range of 1–10 MPa [12]. Nauman et al. [13] reported that the compressive strength of cancellous bone lies in the range of 2–12 MPa. Compressive strength primarily depends on 123