Towards integrated lean, sustainable and smart product design: a systematic literature review

Purpose This study undertakes a systematic literature review (SLR) exploring how the paradigms of lean, sustainable and smart (LSS) product design intersect within the evolving landscape of Industry 4.0. The review aims to trace the development of lean principles, sustainability-oriented strategies and digital technologies, identify where integration among them remains limited and highlight possible pathways for building a unified design framework. To address the temporal mismatch between lean's historical roots and Industry 4.0's digital design logic, the review distinguishes foundational antecedents from Industry 4.0-era integration evidence. Design/methodology/approach The review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) procedure. Searches were conducted across five leading databases – Scopus, Web of Science, IEEE Xplore, Emerald Insight and ScienceDirect – for English-language studies published from 1981 to 2024. Boolean keyword combinations were applied to capture literature on lean product development (LPD), sustainable design and smart or digital design. After duplicate removal and multi-stage screening, 214 peer-reviewed papers were selected. Each study was coded thematically within its respective domain, and a cross-domain synthesis was undertaken to assess the level of integration maturity. Thematic findings were derived through a hybrid content analysis (deductive pillar coding complemented by inductive theme refinement), and integrative claims related to smart/Industry 4.0 were interpreted primarily from post-2011/2015 studies where digital design technologies are substantively present. Findings The review shows that while LSS design approaches have each matured substantially, their systemic integration remains underdeveloped. Lean methods enhance efficiency and value flow but seldom extend to full life cycle or environmental considerations. Sustainable design embeds ecological and social responsibility but is often introduced reactively rather than proactively. Smart design relies on digital enablers such as artificial intelligence (AI), the Internet of Things (IoT) and digital twins to achieve adaptive intelligence yet faces challenges of interoperability and workforce capability. Only around 14% of studies combined more than one paradigm, underscoring limited cross-pollination. Major integration barriers include disjointed measurement systems, methodological silos and a lack of sector-specific frameworks. The analysis identifies five potential pathways that can align lean efficiency, sustainable lifecycle thinking and digital feedback mechanisms within an integrated design approach. These pathways are grounded in recurring patterns observed in the coded literature and are positioned as an evidence-informed research agenda rather than empirically validated prescriptions. Research limitations/implications This review focuses on peer-reviewed sources written in English and excludes patents or grey literature. Future studies should test the proposed pathways empirically, employ longitudinal data and develop quantitative cross-pillar metrics linking lean performance, sustainability impact and digital maturity. Practical implications For practitioners, the synthesis provides a consolidated evidence base demonstrating how LSS methods can be combined in product development. It highlights actionable tool bundles such as the integration of life cycle assessment, design for manufacturability and assembly and digital twin validation along with hybrid design-gate metrics that can support decision-making in industrial contexts. Practical insights are drawn primarily from Industry 4.0-era studies that explicitly incorporate digital feedback and data-enabled governance. Originality/value This review is the first PRISMA-compliant synthesis to systematically unite LSS product design perspectives. By clarifying where integration succeeds or fails, it bridges conceptual scholarship and industrial practice and establishes a structured research agenda for data-driven, sustainable product innovation in the era of Industry 4.0.