*Data-Gathering Method*

The study used articles screened for "titles, abstracts, and keywords" in English from the WoS (Web of Science) database. "Biomimetic(s)", "biomimicry", or "bio-inspired" and "thermoregulation", "energy efficiency", or "envelope/façade" were used as keywords to analyze trends in biomimicry between 2010 and 2021.

A total of 732 items in the specified period were identified. The records were divided into eight classes: articles (569; 77%), review articles (94; 12%), proceedings papers (70; 9%), book chapters (15; 2%), and others such as early access papers, editorial materials, and meeting abstracts. A total of 251 of the items were 'open access' (34%); the remainder were available through subscription.

Articles (148) and review papers (30) under the categories of architecture, construction building technology, energy fuels, ecology, environmental science, interdisciplinary engineering, and multidisciplinary papers were selected for a detailed analysis. A total of 53 research and review articles about biomimicry and energy efficiency in architecture were obtained.

#### **3. Results and Discussion**

The data collected from the WoS database were analyzed based on the year of publication, research area, geographical area, authorships, citations, and the transition of biological phenomena to the architectural products studied.

#### *3.1. Annual Publication Analysis*

Figure 2 presents the distribution of publications by year, demonstrating that research in the relevant subject has intensified, and the number of articles has increased in the last five years. In 2021, 17 articles with the specified qualities were published, and the highest number was reached. Based on the results, more comprehensive research on biomimicry and energy efficiency is needed. On the other hand, the increasing number of articles indicates a growing interest in this field.

#### *3.2. Research Area Analysis*

The pie chart in Figure 3 indicates the thematic classification of biomimicry and energy efficiency in buildings. According to the chart, "engineering" is the most researched topic (24%). Substantial studies were conducted in" building technology, energy studies, materials science, and environmental studies". Additionally, 10% of the total research area distribution consists of studies in computer science, robotics, thermodynamics, urban studies, physics, and chemistry.

**Figure 3.** Subject area distribution of the related literature in biomimicry and energy efficiency.

The highest number of publications is in engineering (23), and construction and building technology (16) is in second place. Additionally, the input from the other areas has been shown clearly (Table 1).


**Table 1.** Publication by research area.

#### *3.3. Geographical Area Evaluation*

Figure 4 shows the countries with publications in the relevant field. While 20 countries contributed to the 52 articles examined, only 5 countries published 6 or more, which shows the inadequacy of such research in many countries. In terms of the number of publications on biomimicry and energy efficiency, Australia, Germany, and the United Kingdom are at the top of the list, then Italy and United States follow them. These five countries account for more than 70% of the publications in this area.

Countries in the top ranks show that economically and technologically strong countries are more active in this field. Some countries' publications appear only as single-country publications. This shows that these countries do not collaborate with other countries. Because more than half of the publications are co-authored, multiple countries may enroll for an article. The authors' collaboration networks show that growth is occurring in a multi-institutional and international way, utilizing the infrastructures accessible in the authors' organizations and countries (Figure 5). After analyzing the articles under the headings of biomimicry and energy efficiency, the results were obtained in the form of three

clusters: the red cluster represents Australia, Chile, Greece, and Italy; the green cluster represents the United Kingdom, France, Spain, and Turkey; and the blue cluster represents Germany, the Netherlands, and the United States. Figure 6 shows the relation between countries and citations. The five countries with the most citations are Germany (304), the United Kingdom (205), the United States (132), Italy (120), and Australia (81), respectively.

**Figure 4.** Countries and the number of publications.

**Figure 5.** Collaboration network between countries.

**Figure 6.** Network connection between citations and countries.

#### *3.4. Analysis of Authorship*

Figure 7 shows the top 10 authors with the most citations of their articles related to biomimicry and energy efficiency in buildings. According to the results obtained from the cluster network, the greatest number of citations (199), with a total link strength of 21, belongs to "Achim, Menges". In this part of the analysis, the identification of the most influential authors was considered. The top 10 authors with the most citations and their link strength are shown in Table 2, and Table 3 shows the 10 most cited articles on biomimicry and energy efficiency. Ideas and processes related to biomimicry and energy efficiency in buildings are presented in these articles. The main focus of the articles is on the energy efficiency of building envelopes according to design approaches.


**Table 2.** Top 10 authors with the highest number of citations.

**Table 3.** Top 10 highly cited papers.


**Figure 7.** Most cited authors.

#### *3.5. Analysis of Organizations*

The performance of organizations with two or more publications in terms of biomimicry and energy efficiency is represented by the graph bar in Figure 8. The University of Stuttgart is the most productive research center with the most publications (6) in the related research area. The Polytechnic University of Bari in Italy, the University of South Wales in the United Kingdom, and the University of Freiburg in Germany each have three publications, while the other organizations have one or two. The list of organizations that have researched in the fields of biomimicry and energy efficiency includes a diverse range of countries. According to Figure 9, Stuttgart University, with 299 citations, has the highest number; the University of Freiburg (148) and Newcastle University (88) follow.

**Figure 8.** Organizational publications in the field of biomimicry and energy efficiency.

**Figure 9.** Visualization of organizations' citation network.

#### *3.6. Citation by Sources*

The relationship between publications and citations is presented in the form of a network visualization in Figure 10. The size of the node is proportional to the number of publications, so the more articles, the larger the size of the node. The highest number of publications (5) and citations (176) belongs to the *Renewable and Sustainable Energy Reviews* journal, with total link strength of 24. It is followed by *Energy and Buildings*, *Buildings*, and *Sustainability*. The distribution of articles classified as biomimicry and energy efficiency in the field of architecture are mostly published in the journals listed in Table 4.

**Figure 10.** Visualization of publication sources' citations.


**Table 4.** List of journals with more than one publication in biomimicry and energy efficiency.

#### *3.7. Co-Occurence of Keywords*

The network diagram shows the keywords in the appropriate publications and their relationships to each other (Figure 11). The keywords analyzed were words that were repeated at least three times in the selected articles. As a result, 39 keywords were obtained in 4 groups. Relating keywords to the main content of the publications is key to revealing trends in research topics. This study found that the authors preferentially used the keywords "Biomimicry" and "Biomimetics". It was also found that the focus of the studies is on different design strategies for thermal performance through building envelopes.

**Figure 11.** Co-occurrence of keywords.

#### *3.8. Content Analysis of the Selected Articles*

In nature-based research, adaptation mechanisms are explored to achieve quantitative and qualitative ideas, such as the transfer of information between scales, programs, processes, or partnerships, and, as a result, a design solution is established. Solving difficulties, such as form, materials, shape, processes, and systems, in this kind of study is confined to the biological knowledge of the designer. Support for such a study by a multidisciplinary team will significantly lessen the challenge of interdisciplinary information transmission.

A content analysis was performed in this part of the research for the articles to better comprehend and remark on biologically inspired studies that altered the energy performance of buildings in the architectural literature as a consequence of multidisciplinary investigations (Table 5).


**Table 5.** Content analysis of articles.


When the 47 directly related articles were examined, innovative designs for the built environment, such as energy efficiency, reductions in energy consumption, water harvesting, thermoregulation, and sensitive and responsive façades and materials, were found to be produced without the help of motors, computerized devices, or external energy sources. The common feature of all these studies is that they aim to minimize the damage to nature, reduce energy consumption, and produce energy-efficient, zero-energy buildings. In this context, it is seen that biomimetic design offers many opportunities for energy-efficient buildings. The main reason why the examined studies mostly focus on the building envelope is that this has properties that require the control of various environmental factors such as ventilation, humidity, heat, light, and mechanical stress, just like shells, the skin, and surfaces in nature. Nature has the potential to provide unlimited examples for the production of sustainable, adaptive, adaptable, and energy-efficient buildings.

According to the Sankey diagram (Figure 12), more than 70% of the approaches to solving the energy problem in buildings are problem oriented. Concepts such as simulations, parametric models, kinetic mechanisms, and computational design are used to transfer the solutions found in nature to architectural designs. The data obtained by analyzing the biomimicry approach, the biological phenomena of nature, and the architectural research based on these phenomena and what topics they cover in energy efficiency are presented through data visualization. In this paper, "information analysis techniques" were used. It can be observed that the architectural studies interact with nature in the framework of a technological perspective and that architecture, biology, and technology are closely linked.

**Figure 12.** Sankey diagram of the biomimetic approach, biological phenomena, transition to architecture, and issues to be solved.
