Bio-inspired interactive kinetic façade: Using dynamic transitory-sensitive area to improve multiple occupants’ visual comfort

The architectural form of the fac¸ade determines its identity as well as interactions with micro-climate forces of the ambient environment, such as solar radiation. The dynamic nature of daylight and occupants’ positions can cause some issues such as heat gains and visual discomfort, which need to be controlled in real-time operation. Improving daylight performance and preventing visual discomfort for multiple occupants simultaneously is challenging. However, integrating the biomimicry principles of morphological adaptation with dynamic, complex fenestration, and human-in-loop systems can lead us to ﬁnd an optimal solution. This research builds on relevant literature study, biomimicry morphological approaches, and parametric simulations, to develop a bio-inspired interactive kinetic fac¸ade for improving multiple occupants’ visual comfort simultaneously, inspired by plant’s stomata movement and behavior principles. Learning from the transitory stage and hunting new position of stomata’s patchy patterns, leads us to identify the dynamic transitory-sensitive area of attraction point on the fac¸ade that is triggered by the dynamic sun-timing position and multiple occupants. The annual climate-based metrics and luminance-based metric simulation results of 810 bio-inspired interactive kinetic fac¸ade alternatives prove that the elastic-deformable-complex-kinetic form triggered by the dynamic transitory-sensitive area can improve the visual comfort of multiple occupants simultaneously. In particular, the bio-inspired interactive kinetic fac¸ade with grid division 8x1 displays extraordinary daylight performance for south direction that


Introduction
Since natural light, as a renewable and permanent source, has positive physical, psychological, and mental effects on occupants' health (ASHRAE Press, 2006;Konis and Selkowitz, 2017b;Tzempelikos, 2017), supplying sufficient useful daylight at interior space is one of the influential subjects for designing facades.Interactive kinetic fac ¸ades, whether adaptive (Loonen, 2015;Lo ´pez et al., 2015) or responsive (Shahin, 2019), change their configurations in response to building's ambient climate and occupants' activity in real-time operation for improving the well-being and productivity of residents."Adaptive building skin refers to a morphogenetic evolution and real-time physical adaptation of a design in relation to its surrounding environment" (Al-Obaidi et al., 2017).Biomimicry and biological strategies, such as plant adaptations, provide underlying principles for proposing climate-adaptive and interactive kinetic fac ¸ade designs' concepts (Han et al., 2016;Houda and Mohamed, 2018;Mazzoleni, 2013).
Biomimicry as "the study of overlapping fields of biology and architecture that show innovative potential for architectural problems" (Radwan and Osama, 2016) has been applied pervasively to explore nature for finding an appropriate logic to develop the unique fac ¸ade idea.Also, biomimicry is defined by Janine (Benyus, 2002) as ''the new science that studies nature's models and imitating these designs to solve human problems".Numerous movable components in nature, including that of plants, animals, and humans, provide adaptability by several motions and transformations.Lacking movements and dependency on a specific location are similar attributes of buildings and plants.However, plants benefit from flexible and curved bodies as well as kinetic components such as leaves and petals (Hosseini, Mohammadi, Rosemann, et al., 2019;Lo ´pez et al., 2015).Hence, the architecture of plants, especially their morphological approach, is a source of inspiration to extract unique adaptive strategies to light (Badarnah, 2017;Houda and Mohamed, 2018).In particular, motion principles detected in plant movement (whether micro or macro scale) can be transferred to a larger scale as technical solutions for the kinetic shading fac ¸ade that change from static to dynamic (Hosseini et al., 2021;Schleicher et al., 2015a).Design rules derived from biological systems provide an opportunity to achieve adaptive morphological change in different ways (Vincent, 2007)."The movement of plants or plant parts occurs over a wide range of sizes and time scales (Forterre, 2013)."For example, the leaves of the Venus Fly Trap have High-speed shutting in 1/25 s (Forterre, 2013;Ko ¨rner et al., 2018).Similarly, an adaptive shading fac ¸ade is inspired by the hinge-less motion of the underwater snap trap of Aldrovand Vesiculosa (Ko ¨rner et al., 2018).Due to existing buildings, Council House 2 in Melbourne is inspired by tree organisms and their behavior.This biomimicry approach results on energy savings of 82% and reduces energy use for artificial light and mechanical ventilation by 65% (Radwan and Osama, 2016).
Investigation of daylighting guide systems inspired by biomimicry provides an extensive range of information about building scale, system and movement types, influential elements, geometric form, functions, ways of admitting daylight, and climate.Generally, daylighting guide systems inspired by biomimicry have been used in different climates especially temperate and warm-desert based on Koppen climate classification (Chen and Chen, 2013).The systems are used for making adaptive and responsive envelope, and kinetic shading facades (Lo ´pez et al., 2015;Shahin, 2019).They frequently applied complex, flexible, foldable, and hierarchical self-shading forms using smart and semitransparent materials (Badarnah et al., 2010;Ko ¨rner et al., 2018).The geometric forms can be divided into three groups: a) complex form, b) convertible structure, and c) hierarchical structure.Complex forms are used pervasively, while hierarchical self-changed structures demonstrate a growing trend.The main functions are real-time daylight control, sufficient supply of daylight, daylight performance, glare protection, and thermal regulation (Schieber et al., 2017;Schleicher et al., 2015a;Xing et al., 2018).However, aesthetics, privacy protection, and visual contact to the exterior are also topics under development.The influential elements benefit from morphology, responsiveness, and smart materials.The responsive systems use programmable actuation for sensing and self-transformation.The fac ¸ade morphology (which triggered by the responsive system) is transformed based on elastic deformation (Pohl and Nachtigall, 2015a;Schieber et al., 2017;Schleicher et al., 2015b), moveable components (Badarnah et al., 2010), shape-changing panels (Xing et al., 2018), and self-shading geometries (Hertzsch, 2010;Pohl and Nachtigall, 2015c).In summary, an efficient daylighting system can be extracted from the fac ¸ade's components in grid forms.The fac ¸ade needs to be kinetic under the navigation of a responsive decentralized system to provide a hierarchically self-shading form resulting in a bio-inspired interactive fac ¸ade with respect to users (occupants).
Due to the high-potential of the biomimicry approach for extracting technical solutions and the "lacking quantitative performance analysis of bio-adaptive building skins" (Kuru et al., 2019), there is an opportunity for developing an interactive logic to provide a communication between multiple occupants positions and dynamic sun-timing S.M. Hosseini, M. Mohammadi, T. Schro ¨der et al.
positions.Moreover, the logic can be applied into kineticresponsive decentralized and human-in-loop systems for improving multiple occupants' visual comfort simultaneously (Fig. 1).This research aims to develop an interactive kinetic shading fac ¸ade to improve multiple occupants' visual comfort simultaneously inspired by plant's kinetic movements and behavior.Therefore, the current research will be conducted through the following questions: What are the characteristics of kinetic shading facades inspired by biomimicry?How can the biomimicry principles from the plant inspire fac ¸ade form's configuration to improve occupants' visual comfort simultaneously for multiple occupants' positions?

Method
This research builds on a relevant literature study, a biomimicry morphological approach, and parametric simulation to develop a bio-inspired interactive kinetic fac ¸ade for improving multiple occupants' visual comfort simultaneously.The first part of the research (Section 3) uses Google scholar and Scopus to represent the main theory of the kinetic movement and behavior through biomimicry.Furthermore, in Sections 3.2 and 3.3, the study applies the biomimicry morphological approach (Badarnah, 2017) to design the interaction of the kinetic fac ¸ade inspired by stomata distribution and movement.The third part (Section 4) of the study performs comprehensive Daylight performance simulations of parametric bio-inspired interactive kinetic facade alternatives (810 different cases) to investigate the improvement on visual comfort of multiple occupants simultaneously.Moreover, their daylight performance and visual comfort are studied through climate-luminance based daylight metrics using daylight performance prediction guidelines from Reinhart (Reinhart, 2011(Reinhart, , 2019)).The metrics applied in the study consist of spatial Daylight autonomy (sDA), Useful Daylight Illuminance (UDI), Exceed Useful Daylight Illuminance (EUDI), and Daylight Glare Probability (DGP).This research aims to propose an approach for integrating biomimicry principles of morphological adaptation with dynamic and human-inloop systems for improving occupants' visual comfort.The well-known software and plugins Rhino 6, Grasshopper and Diva 4 are used to evaluate daylight performance.

Developing a bioinspired interactive kinetic fac ¸ade through biomimicry morphological approach
Biomimicry levels are categorized as physiology, morphology and behavior (Badarnah, 2017), thus, detecting suitable analogies significantly depends on exploring the appropriate level.Many researches applied biomimicry morphological level to design facades that adapt to the ambient environment using complex and flexible forms (Al-Obaidi et al., 2017;Badarnah, 2016aBadarnah, , 2017;;Brodoceanu et al., 2016;Charpentier et al., 2017;ElDin et al., 2016;Knippers and Speck, 2012;Ko ¨rner et al., 2018;Li and Wang, 2016;Lo ´pez et al., 2017;Pohl and Nachtigall, 2015b;Rivie `re et al., 2017;Schieber et al., 2017;Speck et al., 2017), convertible elements (Charpentier et al., 2017;Knippers and Speck, 2012;Pohl and Nachtigall, 2015b), and hierarchical structures (Knippers and Speck, 2012;Schieber et al., 2017).A variety of well-designed self-shading forms in nature can be found in plants.For example, the vertical fleshy ribs of cactus provide a self-shading form that adapts to harsh climate by reducing incident solar radiation (Hertzsch, 2010).Combination of bio-inspired forms and their transformability characteristics provide an opportunity to create new fac ¸ade systems that are intelligent (Li and Wang, 2016;Speck et al., 2017), responsive (Ko ¨rner et al., 2018), and adaptive (Al-Obaidi et al., 2017;Badarnah, 2016bBadarnah, , 2017;;ElDin et al., 2016;Lo ´pez et al., 2015;Schieber et al., 2017) to environmental conditions.To illustrate, based on Badarnah (Badarnah, 2017) conclusion that "form follow environment", the mimicking extensibility of plant cells' walls in the shape of Voronoi patterns results in a Bio-interactive fac ¸ade's complex form.This fac ¸ade can hierarchically change scale and extrude modular elements for real-time daylight control (Fig. 2).Since responsive fac ¸ades have to interact with external and internal stimuli, plant adaptation principles can be recognized as an influential source for generating interactive kinetic fac ¸ade forms to improve occupants' visual comfort (Houda and Mohamed, 2018).

Stomata
Many plants possess unique adaptions for sensing and reaching adequate sunlight as well as coordinating wholeplant growth by enabling greater photosynthesis efficiency (Aanuoluwapo and Ohis, 2017;Burris et al., 2018).The elastic and dynamic movements of plants can inspire kinetic shading fac ¸ade systems that interact to internal and external stimuli through morphological adaptation (Prabhakaran et al., 2019).Although plants benefit from their flowers and leaves in the macro-scale to adjust angle and orientation with respect to sunlight, exploring plants in the micro-scale provides an opportunity to detect optimal principles for future resilient building design."Plant cell walls are highly dynamic structures offering dynamic and multiple functionality (Xing et al., 2018)."In particular, stomata of plant's leaves open and close to facilitate photosynthesis by controlling gas exchange, air humidity and light between plant and environment (Ho ˜rak et al., 2017;Lo ´pez et al., 2017;Prabhakaran et al., 2019).Stomata are pores in the surface of aerial parts of higher plants that are made by a pair of the guard cells and neighboring subsidiary cells.Their influential functions allow an adequate amount of CO 2 to enter the leaf while conserving as much water as possible (Willmer and Fricker, 1996a).Stomata locate in equidistant and regular rows and their pores are considerably symmetrical."Stomata frequency, according to cell size and smaller guard cells can be modified by environmental factors and leaf morphology" (Willmer and Fricker, 1996b) (Fig. 3a).Intrinsic and extrinsic factors cause a general variability in stomatal aperture and size resulting in heterogeneity in biological systems for achieving adaptability.Sudden environmental conditions' changes give rise to patchy behaviors of stomata.The patchy pattern has a transitory stage that hunts for new conditions and positions in response to immediate environmental changes.The stomata within the area react in harmony and independency from neighboring areas (Fig. 3b).Hence, optimized apertures in size and shape maintain the stable internal conditions while tolerating external changes (Willmer and Fricker, 1996b).

Designing interaction of the kinetic fac ¸ade inspired by stomata distribution and movement
The interactive kinetic fac ¸ade inspired by stomata distribution and movement can meet the daylight performance and visual comfort requirement.The kinetic fac ¸ade configuration is interactive due to the use of dynamic  Phase 1) Regular and equidistance rows of stomata allow applying the grid form and positioning of kinetic elements in the fac ¸ade surface (Fig. 5).
Phase 2) Defining the logic of multiple dynamic attraction points in the fac ¸ade by following two steps (Fig. 6): a) Making a user field of the vision (UFV) line between the sun (timing) position and occupants' positions in the office; and b) Identifying the intersection points between the UFV lines and the fac ¸ade surface as the attraction points.
Phase 3) Generating complex form triggered by a dynamic transitory-sensitive area (TSA) of attraction point (Fig. 7) (inspired by Stomata patchy pattern transitory stage (Fig. 4)): a) Transitory-sensitive area is defined as a region of the fac ¸ade in which the kinetic elements within the area react in harmony and entirely independent from neighboring areas; b) The center of the TSA is determined by the attraction point's position; c) The shape of the TSA is   assumed as a circle; d) The radius range of the TSA can be changed from 0.1R to R with an interval of 0.1; e) The amount of R is defined as a maximum distance between the attraction point and the farthest kinetic element on the fac ¸ade; f) Depth and rotation of the kinetic elements within the TSA are hierarchically changed based on their distance from the attraction point; g) The number of TSA in the fac ¸ade is equal to the number of the occupants; h)The dynamic characteristic of the TSA generates an interactivekinetic-complex-hierarchy-self-shading form.
Figure 6b presented the kinetic concept of the system through several views consist of top, front, and perspective.The kinetic elements are positioned in grid forms with equal distances that take hierarchy movements in depth and angle based on their distances from the attraction point within the TSA area (Table 1).Elements which that were placed out of the TAS, remained without any movements.According to Fig. 6c, structure of the biomimetic fac ¸ade has been constructed by a single span frame which has some rail profiles made from stainless steel in between.Moving mechanisms on the side rail provide two functions including a connection between the kinetic elements and rail profile, and their horizontal movements on the rail.The kinetic elements have different movement options and supplying connection tools for holding the tensile material.(Reinhart, 2019).sDA is identified as "the percentage of the occupied hours of the year when a minimum illuminance threshold is met by daylight alone" and for a point to be considered 'daylit,' the sDA at the point has to be 50%, in short sDA 300 lux [50%] (Reinhart, 2019).UDI is defined when "there is useful daylight in the back two-thirds of the space (UDI 100-3000 Lux), while EUDI (UDI > 3000 Lux) flags on over-supply of daylight near the fac ¸ade" (Reinhart, 2011(Reinhart, , 2019)).Glare is a human sensation, defined by Harper Collins, "describes light within the field of vision that is brighter than brightness which the eyes are adapted (Reinhart, 2011)".The increasingly popular discomfort glare metric suggested by Wienold and Christofersen (Reinhart, 2019;Wienold and Christoffersen, 2006) is Daylight Glare Probability, which uses "CCD Camera based luminance mapping technology."Furthermore, DGP has been categorized into four groups comprising imperceptible (30e35), perceptible (35e40), disturbing (40e45) and intolerable (45e100) (Reinhart, 2011).In particular, DGP has been measured at points assigned to occupants' positions in the room.
The simulation is performed using Rhinocerosâ, Grasshopper, and Diva for analyzing daylighting and energy modeling.The simulation is made assuming that the office building is located in Yazd, Iran.Yazd has been classified as a hot desert climate (BWh), which has clear sky based on Koppen climate classification (Chen and Chen, 2013).Furthermore, Yazd weather data used for the simulation process are available from the EnergyPlus website and arranged by the World Meteorological Organization region and Country (National Renewable Energy Laboratory, 2019).The width and depth of the floor plan are respectively 4.4 m and 4.1 m based on the standard office layout (Neufert and Neufert, 2000).Building elements are modeled with a thickness of 0.2 m for walls, 0.3 m for ceiling and floor (Fig. 9).The height of the room from the top of the floor to the bottom of the ceiling is 2.8 m.Moreover, the window is located on the south fac ¸ade with a ratio of 0.  (Reinhart, 2011(Reinhart, , 2019)).Also, basic elements for studying daylight performance simulation defined in Table 2.The following assumptions are applied to the daylight performance simulation: clear sky with sun, minimum of 300 Lux on the work plane in height of 0.85 m from the floor, occupancy schedule (8e16), a grid of sensors will be 0.5 m wide in Y and X directions, no shading and artificial light (Reinhart, 2011).

Base case (plain window room)
The evaluation of daylight performance of plain window (base case) through climate-based daylight metrics show that not enough useful daylight is provided to satisfy occupants' requirements.Although enough daylight is admitted into the room (satisfactory sDA 93.8% of the time), the UDI amount (16.66%) indicates that most of the admitted light is higher than 3000 Lux, resulting in visual & thermal discomfort.A value of EUDI (76.75%) proves the results.For the prediction of risk of glare, most of the cases are in the intolerable range (Table 3).Table 3 indicates the complete visual discomfort for the occupants who suffer from daylight glare throughout the year.

Bio-inspired interactive kinetic facades' results
The simulation results of 810 bio-inspired interactive kinetic facades (BIKF), with the several grid divisions of 4x1, 8x1, 12x1, confirm the significant improvement in visual comfort and daylight performance, due to different size of the TAS, compared to the base case.Since the TSA influenced by dynamic sun timing and occupants' positions, the BIKF changes its configurations in the timing individual scenario which equal 9 different fac ¸ade's forms.As we have 10 distinctive radiuses of the TSA, thus all the possible configurations for every grid division are 90 cases.The simulation results have been filtered based on the minimum sDA of 50% with 1% safety and maximum EUDI of 10% to identify the optimal BIKF with specific transitory sensitive area's radius for different directions consisting of west, east and south.
Tables 4e6 represent the percentage of climaticluminance based daylight metrics (sDA, UDI, EUDI) on the solstice and equinox days (at 9, 12, 15) for the best options of BIKF with 4GD, 8GD, and 12GD of every direction.

Bio-inspired interactive kinetic fac ¸ade's result for the west direction
The simulation results confirm the high performance of the kinetic interactive fac ¸ade for improving visual comfort regarding the base case.In this case, the kinetic fac ¸ade changes its configuration using hierarchical rotating movements of modular elements to control daylight regarding sun and occupant positions based on different daytime    11).

Bio-inspired interactive kinetic fac ¸ade's result for the south directions
Analyzing the daylight performance numbers in Table 6 reveals the significant effects of dynamic transitorysensitive area (TSA) with radiuses of 0.3R and 0.5R of 8, and 4 grid divisions respectively to improve multiple occupants' visual comfort (Fig. 12).The BIKF 4GD with TSA's 0.5R shows the high capability to meet annual daylight metrics' requirements including sDA, UDI, and EUDI with an average percentage of 54.8, 82.05, and 13.16 respectively.In contrast, the BIKF 8GD with TSA's 0.3R improves the amount of sDA, UDI, and EUDI with the average number of 60.55 and 90.46, and 2.94 respectively.It refers to the highperformance of the BIKF for meeting occupants' daylight performance by an improvement of 4.43 times in increasing UDI and decreasing the EUDI up to 96.15% compared to the base case while keeping sDA in the satisfactory range.Moreover, the BIKF 8GD with TSA's 0.3R improves the amount of sDA and UDI by the percentage of 10.49% and 10.25% respectively while decreases the amount of EUDI up to 3.47 times respecting the 4GD with TSA's 0.5R (Fig. 12).In particular, the kinetic facade has 7 cases in the imperceptible, and 2 cases in the perceptible ranges (Fig. 13a).
To sum up, the BIKF with 8 grid division provides maximum useful daylight in the interior space while preventing visual discomfort as well as overheating nearby the fac ¸ade for the south direction.
Figure 13b displays a remarkable effect of the TSA with a radius of 0.3R to achieve an optimal configuration due to the improvement of visual comfort in the BIKF with 4 grid divisions for the east direction.Analyzing the luminancebased metrics diagram mentions the high capability of BIKF to keep daylight glare probability in the acceptable ranges.The BIKF has 7 cases in the imperceptible, and 2 cases in the perceptible ranges for occupant's number two while 5 cases in the imperceptible, 2 cases in the perceptible, and only 1 case in the disturbing ranges for occupants' number one and three.
Considering Fig. 13c indicates the high capability of BIKF 4 grid divisions with TSA radius of 0.3R to meet visual comfort requirements respecting daylight glare probability evaluation for west directions.The BIKF has 6 cases in the imperceptible, 2 cases in the perceptible, and 1 case in the intolerable ranges for occupant's number two while 5 cases in the imperceptible, 2 cases in the perceptible, and only 1

Discussion
Since an optimal facade form significantly affects the amount of useful daylight, it presents an opportunity to investigate and develop real-time form findings logics.In particular, buildings, which have high daylight performance apply dynamic, complex fenestration, and human-in-loop systems (Hosseini, Mohammadi and Guerra-Santin, 2019;Hosseini, Mohammadi, Rosemann, et al., 2019;Konis and Selkowitz, 2017a).The fac ¸ade needs to be kinetic and interactive under the navigation of a responsive decentralized system to provide a hierarchically self-shading form resulting in an interactive fac ¸ade due to user engagement (occupants).Since the interactive kinetic fac ¸ade function (improving visual comfort) has been proved through annual climate based metrics and luminance-based metric (Reinhart, 2011) simulation only for a single occupant in different positions of a test room.Fac ¸ades need to be kinetic under the navigation of a responsive decentralized system to provide a hierarchically self-shading form resulting in a bio-inspired interactive fac ¸ade with respect to occupants.Due to the high-potential of biomimicry approach for extracting technical solutions and lacking quantitative performance analysis of bio-adaptive building skins, this research aims to develop an interactive kinetic shading fac ¸ade, for the first time, to improve multiple occupants' visual comfort simultaneously inspired by plant movements.
The interactive kinetic fac ¸ade, inspired by stomata distribution and movement, has the capability to meet the daylight performance and visual comfort requirement for multiple occupants.Indeed, the abstraction of biomimicry principles from stomata's general characteristics, and stomata patchy pattern transitory stage can propel the development of the real-time morphological logic for the interactive kinetic fac ¸ade design.Regular and equidistance rows of stomata give rise to apply grid form and positioning of kinetic elements in the fac ¸ade surface.Also, the transitory stage and hunting new position of stomata's patchy pattern, leads to identify the dynamic transitory-sensitive area (TSA) which is triggered by the dynamic sun-timing position and multiple occupants.Accordingly, the elasticdeformable-complex-kinetic form triggered by the dynamic TSA of attraction point (Figs.5e7) can improve the visual comfort of multiple occupants simultaneously.
The parametric simulation results of 810 bio-inspired interactive kinetic facade (BIKF) alternatives, with the several grid divisions of 4x1, 8x1,12x1 in three different directions (south, east, and west), prove the significant improvement in visual comfort and daylight performance of multiple occupants, due to different size of the TAS, compared to the base case.Due to annual climate-based daylight metrics evaluation specifically Spatial Daylight Autonomy (Minimum 50%), we can categorize the BIKFs alternatives into two groups: 1) Gird divisions 4x1, 8x1, 2) Grid divisions 12x1.The first group can provide adequate daylight and prevent visual discomfort while the second group cannot supply enough daylight.Indeed, this fact emphasizes that having more kinetic components can't guarantee the daylight performance of the fac ¸ade.
The first group that has the BIKFs with the grid divisions 4x1, 8x1 demonstrates high performance for supplying adequate daylight in the interior space while preventing visual discomfort specifically through using the TSA's radiuses in different ranges.Annual climate-based metrics and luminance based metric evaluations infer the significant impact of the transitory-sensitive area with different radiuses to achieve a compromised configuration in the BIKF alternatives.Due to the grid divisions, the acceptable ranges of TSA's radiuses for improving multiple occupants' visual comfort are recognized consist of 0.3-0,6R for grid division 4x1, 0.1e0,3R for grid division 8x1.In particular, the BIKF with grid division 8x1 and TSA's 0.3R displays extraordinary daylight performance which is recognized as the best case between the first group for the south direction.This alternative prevents visual discomfort with having 7 cases in the imperceptible, and 2 cases in the perceptible ranges while providing adequate average sDA of 60.5%, UDI of 90.47%, and EUDI of 2.94% indeed, it mentions to the high potential of this BIKF to admit adequate useful daylight and preventing thermal discomfort while keeping the DGP values of all occupants in the acceptable ranges.Regarding the east and west directions, BIKFs with the grid divisions 4x1 shows the remarkable daylight performance.Especially, the BIKF with TSA's radius of 0.3R has 7 cases in the imperceptible, and 2 cases in the perceptible ranges while providing adequate average sDA of 49.56%, UDI of 83.28%, and EUDI of 13.1% for the east orientation.In addition, the BIKF has 6 cases in the imperceptible, 2 cases in the perceptible, and 1 case in the intolerable ranges for the west direction.The facade can supply average sDA of 50.29%,UDI of 87.26%, and EUDI of 10.10% as well.
The second group includes the BIKFs with the grid divisions 12x1(TSA's 0.1R) can't meet the minimum sDA with the percentage of 2.16, 1.72, 26.81 for the west, east, and south directions respectively.However, the fac ¸ade show the high capability for preventing visual discomfort that have 8 cases in imperceptible and 1 case in perceptible ranges.Since admitting adequate daylight is the priority for choosing the best options for improving visual comfort, thus the BIKFs with the grid divisions 12x1 is not a proper choice for the bio-inspired interactive kinetic fac ¸ade.
The study focuses on the concept design as an influential part of the kinetic design strategy that provides an idea to change from static into dynamic.This research is a fundamental study that shows how using a biomimicry morphological approach can lead to developing an interactive design for improving communication between the dynamic parameters to achieve multiple occupants' visual comfort.The findings of this study have to be seen in light of some limitations.A detailed study needs to be conducted for investigation of sensors correlation and interferences, different shapes of TSA such as the non-conventional one (patchy patterns), different sizes for each of the TSA areas, relationships with other dynamic characteristics of occupants besides the positions.The concentration of this manuscript is more on the formal concept which might be supported with further discoveries in material and structural science.The existence of kinetic structures, such as a wind-walking structure that walks in response to the wind (Kamil Sharaidin, 2014), can strengthen the possibility of materialization of the bio-inspired interactive kinetic fac ¸ade.Due to methodology, the study just applied the parametric daylight simulation based on the daylight performance prediction guideline for evaluating occupants' visual comfort, the same as ongoing worldwide research.However, since the prediction of glare, as an important metric depends on a human sensation, the function of the interactive kinetic fac ¸ade needs to be investigated through experimental study as well.

Conclusion
Reviewing the literature reveals a Lack of the interactive logics of kinetic facades for improving multiple occupants' visual comfort simultaneously.Due to the dynamic characteristics of influential parameters, such as sun-timing positions, local climate variation, and multiple occupants' positions, it is imperative to increase the flexibility and performance of the automated process in the fac ¸ade design.Applying an interactive logic is a way to facilitate communication between the dynamic parameters.The design concept of kinetic shading fac ¸ade can benefit from the biomimicry morphological approach for developing an interactive logic to change from static to dynamic.Hence, the architecture of the plant, especially motion principles of stomata in micro-scale, is a source of exploring and extracting unique adaptive strategies to light.This research aims to develop an interactive kinetic shading fac ¸ade, for the first time, to improve multiple occupants' visual comfort simultaneously inspired by the plant's kinetic movements and behavior.Integrating biomimicry morphological principles with kinetic-responsive decentralized, and human-in-loop systems provide an opportunity to develop an interactive kinetic fac ¸ade with complex geometry.
Considering the functional convergence between buildings and plants regarding daylighting and visual comfort reveals that the plant's stomata filter and harness daylight through different ways consist of interception, redirection, scattering, and transmission.Due to stomata kinetic movements and behavior, there are many options to control daylight comprising symmetrical pores, regular and equidistant rows, transitory sensitive area, reacting in harmony within the area and independent from neighboring areas, hunting new position and shape due to immediate changes in the environment.The extracted movements and kinetic behaviors are translated into the design solutions consist of grid form, symmetrical elements, identification of a dynamic transitory-sensitive area (TSA), dynamic sizes and positions of TSA, defining the logic of dynamic multiple TSA, locally decentralized facades' shape change.
Learning from the plant's stomata movements and behavior directs us to identify the transitory-sensitive area of attraction point on the fac ¸ade.The TSA is triggered by sun timing and multiple occupants' positions that has the capability for controlling the interactive fac ¸ade as well as a real-time generating complex form.The proposed interactive logics improves the performance of the interactive kinetic fac ¸ade for meeting visual comfort requirement from a single occupant to multiple occupants by employing biomimicry morphological approach.The parametric daylight simulation of 810 bio-inspired interactive kinetic fac ¸ade (BIKF) alternatives proves the high-performance of the elastic-deformable-complex-kinetic form triggered by the dynamic transitory-sensitive area.In particular, the bioinspired interactive kinetic fac ¸ade with grid division 8x1 displays extraordinary daylight performance for south direction that prevents visual discomfort by keeping cases in the imperceptible range while providing an adequate average Spatial Daylight Autonomy of 60.5%, Useful Frontiers of Architectural Research 10 (2021) 821e837 Daylight illuminance of 90.47%, and Exceed Useful Daylight illuminance of 2.94%.Regarding the east and west directions, BIKFs with the grid divisions 4x1 shows the remarkable daylight performance.Especially, the BIKF with TSA's radius of 0.3R provides adequate average sDA of 49.56%, UDI of 83.28%, and EUDI of 13.1% for the east orientation while supplying average sDA of 50.29%,UDI of 87.26%, and EUDI of 10.10% for the west side.
Since the shapes and areas (circle) of both TSA on the individual fac ¸ade case are the same, we propose investigation about different sizes and shapes of the TSA for every attraction point at the same time as future research.Regarding the architectural design viewpoint, there is an opportunity to develop the BIKF with TSA through various subjects including proportion, scale, relation to the human body, usability, materiality, haptics, feel the atmosphere, etc. Learning from biological analogies is a precious resource for architects and engineers to develop innovative solutions for architectural design problems.Hence, a close collaboration of biologists, engineers, and designers can support interdisciplinary topics resulting in constructing multi-functional buildings' components.Due to the optimization, the interactive behavior of the kinetic fac ¸ades has the potential to be improved using a reinforcement learning method.Machine learning methods can be applied to predict the optimal functions of the kinetic fac ¸ade based on the dynamic characteristics consist of occupants' behavior, positions, sun-timing positions and dynamic orientations, space functions, and layout design., etc.

Declaration of competing interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Fig. 2
Fig. 2 Mimicking extensibility of plant cell walls in Voronoi patterns resulting bio-interactive facade complex form.

Fig. 1
Fig. 1 Improvement the performance of the interactive kinetic fac ¸ade for meeting visual comfort requirement from a single occupant to multiple occupants by employing biomimicry morphological approach.

Fig. 3
Fig. 3 Identification of appropriate biomimicry principles from Stomata of plant's leaf: a) Stomata general characteristics, b) Stomata patchy pattern transitory stage.

Fig. 5
Fig. 5 Regular and equidistance rows of stomata give rise to apply grid form and positioning of kinetic elements in the fac ¸ade surface.
First, an aluminum telescopic bar controls the depth of the element.Second, a rotational joint changes an angle between two telescopic bars.Third, the two aluminum telescopic bars, as the angle sides, can be contracted and extracted based on their distances from the attraction point position.Finally, the tensile material can be expanded and stabled by the connection tools on the telescopic bars to cover the whole of the fac ¸ade surface.The combination of the telescopic bars and the rotational joint movements provides an exceptional opportunity to change the fac ¸ade configuration through several kinetic options.Therefore, the biomimetic kinetic fac ¸ade can regulate occupants' visual comfort based on dynamic sun positions and occupant positions.

Fig. 7
Fig. 7 Generating complex form triggered by a dynamic transitory-sensitive area (TSA) of attraction point (inspired by Stomata patchy pattern transitory stage).
Fig. 8 Influential parameters for generating bio-inspired interactive kinetic facade alternatives.

Fig. 9
Fig. 9 Test room, occupant positions, direction of views, and attraction points.
4.3.4.Luminance based metric evaluation of the best bioinspired interactive kinetic fac ¸ades of South, East, and West directions Figure 13 displays the DGP value of the best bioinspired interactive kinetic fac ¸ades of South, East, and West directions based on occupants sitting position at the room on the solstice and equinox days.The BIKF forms show significant performance for preventing visual discomfort by decreasing Daylight Glare Probability (DGP) compared to the base case on different days and hours.The BIKF 8 GD with TSA's 0.3R indicates the substantial improvement of DGP values while keeping the sDA in the acceptable ranges.

Fig. 10
Fig. 10 The average daylight performance evaluation of Bioinspired interactive kinetic fac ¸ade through climate-based daylight metrics for the West direction.

Fig. 11
Fig. 11 The average daylight performance evaluation of Bioinspired interactive kinetic fac ¸ade through climate-based daylight metrics for the east direction.

Fig. 12
Fig. 12 The average daylight performance evaluation of Bioinspired interactive kinetic fac ¸ade through climate-based daylight metrics for the south direction.

Table 1
Rotation and sliding movements of kinetic elements in 4 grid divisions based on the given points on Fig.6b.

Table 3
Plain window room daylight performance Glare probability evaluation for different scenarios based on suntiming position and occupant position.