Parasitic Technologies

PARASITIC TECHNOLOGIES_ building facade design using piezoelectric technologies to harvest wind energy TEAM MEMBERS Professor Margaret Kirk, Lead Researcher Jennifer Mahan, Architecture Student and Research Assistant roles_ array design, fabrication, device testing Liam Chaffey, Mechanical Engineering Student and Research Assistant roles_materials research, formal generation, array design Christian Aguirre, Electrical Engineering Student and Research Assistant roles_ device testing, material research, electronics management Raul Garcia, Electrical Engineering Student and Research Assistant roles_ device testing, material research, electronics management

ABSTRACT This project addresses the challenges of designing energy-producing faรงade systems using responsive materials. It intendsto explore the implementation of additive technologies upon existing urban infrastructure in order to exploit the resources of cities, such as the stack effect from the city grid, in order to make a more towards sustainability. Arrays of wind technologies would allow greater surface area to be covered, making the vertical surfaces of cities viable collectors of resources and feed back into the city infrastructure.

Presented is a series of iterations testing energy production using different electric generators. These generators are intended to attach onto existing building facades and link into an array to create a secondary facade system which would collect wind energy produced in high-density urban areas to help power the building they are affixed to. The tests and their results are discussed, as well as the overall intentions to intended to question the role of sustainable technologies within the urban fabric.

1_ INTRODUCTION This project is intended to redefine the role of the facade as a working element and change the experiences from the street level. This calls to question the role of design and how it pertains to sustainability and the incorportation of applied elements into our experience of space and its affect on place. It makes sustainability a three-dimensional consideration. Design is the power to build our experience, so how can we do that with applied sustainable technologies and make them integraphto that experiencethrough design?

1.1_ WIND ENERGY Turbulent flow is the irregular fluctuation of water, air, or some fluid, wherein the speed of the fluid at a point is continuously undergoing changes in both magnitude and direction. Tall structures in high-density urban areas disrupt the otherwise laminar flow of prevailing winds in the area, creating turbulence. These patterns prove advantageous for capturing wind energy in these high-density urban areas. Types of turbulence built up around structures are as follows:

• Downwards deflection • upwards deflection (causing high wind speed) • flow through narrow spaces between buildings (“Venturi effect” - causing high wind speed and high turbulence) • Low velocity eddies on the downwind side of structures • Counter-current effects (reversed or cross-wind direction)

RASITIC C H L O G I E S wind patterns between buildings1

typical incoming winds through New York City

TYPICAL WIND DIRECTION THROUGH NYC

PLEMENTATION OF ADDITIVE TECHNOLOGIES UPON EXISTING URBAN INFRASTRUCTURE IN CES OF CITIES, SUCH AS THE STACK EFFECT FROM THE CITY GRID, IN ORDER TO MAKE A MOVE

1.2_ BIOMIMICRY IN WIND TESTING

ON TO EXISTING BUILDING FACADES AND LINK UP TO CREATE A SECONDARY FACADE SYSTEM. LT TECHNOLOGY, GREATER SURFACE AREA WOULD BE COVERED, MAKING THE VERTICAL LECTORS OF RESOURCES AND FEED BACK INTO THE CITY INFRASTRUCTURE.

ON

Biomimicry derives from the Greek words bios, or life, and mimesis, or imitation. It is emulating behaviors, patterns, and strategies naturally apparent to produce better materials, structures, systems, products, and processes in the designed world. It is using the convergence of evolution thus far in hopes of creating more sustainable solutions to human problems. The origins of this wind-affected project lie in biomimicry.

1.2.1_ CACTI

Certain species of cacti are known to survive brutal wind forces in desert, largely due to their vertical pleats. ncoming wind is diffused as it passes through the spines on the outside edges of cacti pleats. This diffused wind blows to around the pleat, spiraling and forming an opposing turbulent vortex inches off the cactus. Wind AXON that does get through gets diffused up the vertical pleats, stabilizing the cactus. Additionally, cactus spines are break up evaporative winds blowing across their surfaces. See image at right.2 These behaviors prove beneficial in the context of capturing turbulent wind flow in cities, as cacti behave similarly to structures in high-density areas. Their linear pleats serve as a model for how to arrange a facade array upon an existing structure. In addition to the wind already hitting the faces of existing structues, designing to add turbulence to the facade would maximize the energy that could be gathered from an implementation.

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USING AGmbH, DERIVATION ONrheologic.net/en/urban-wind-assessment.

A WIND BELT, A RELATIVELY NEW ADDITION TO WIND POWER “Wind Assessment for Urban Planning and Architecture.” Rheologic, Rheologic 2018,

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A THREE-DIMENSIONAL GATHERING FROM MORE POINTS OF WIND “Cacti / Desert Succulents.” National Parks Service, U.S. Department ofINTO the Interior, 25 Jan. 2016,SYSTEM, www.nps.gov/arch/learn/nature/cacti.htm

TECHNOLOGIES, THIS PROJECTS TURNS A TRADITIONALLY ONE-DIMENSIONAL SYSTEM

CONTACT FROM A SMALLER FOOTPRINT ON MULTIPLE BELTS. THIS TECHNOLOGY IS SUITABLE FOR URBAN USE AS IT IS OPTIMAL AT LOWER WIND SPEEDS AND FROM WIND COMING FROM MULTIPLE DIRECTIONS AS IS THE CASE IN A CITY ENVIRONMENT

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2_ WIND BELT ELECTRIC GENERATOR Professor Kirk began research - “Parasitic Technologies” in 2012 with Pratt’s Faculty Development Fund. These tests began with a derivation on a wind belt, at the time a relatively new addition to wind power technologies.

Wind belts generate electricity when a ribbon-like membrane inside the micro-generator of the belt vibrates due to contact with wind. Professor Kirk designed a housing component to host several belts, which turned a traditionally one-dimensional system into a three-dimensional system - gathering from more points of wind contact froma smaller footprint on multiple belts. This technology proved suitable for urban use as it optimizes at lower wind speeds and from incoming multi-directional wind, as is the case in a turbulent city environment.

THIS PROJECT REDEFINES THE ROLE OF THE FACADE AS A WORKING ELEMENT AND CHANGES THE EXPERIENCE FROM THE STREET LEVEL. THIS CALLS TO QUESTION THE ROLE OF DESIGN AND HOW IT PERTAINS TO SUSTAINABILITY AND THE INCORPORATION OF APPLIED ELEMENTS INTO OUR EXPERIENCE OF SPACE AND ITS AFFECT ON PLACE AND MAKES SUSTAINABILITY A THREE-DIMENSIONAL CONSIDERATION. DESIGN IS THE POWER TO BUILD OUR EXPERIENCE, HOW CAN WE DO THAT WITH APPLIED SUSTAINABLE TECHNOLOGIES AND MAKE THEM INTEGRAL TO THAT EXPERIENCE THROUGH DESIGN?

a proposed facade array located in New York City

THIS PROJECT REDEFINES THE ROLE OF THE FACADE AS A WORKING ELEMENT AND CHANGES THE EXPERIENCE FROM THE STREET LEVEL. THIS CALLS TO QUESTION THE ROLE OF DESIGN AND HOW IT PERTAINS TO SUSTAINABILITY AND THE INCORPORATION OF APPLIED ELEMENTS INTO OUR EXPERIENCE OF SPACE AND ITS AFFECT ON PLACE AND MAKES SUSTAINABILITY A THREE-DIMENSIONAL CONSIDERATION. DESIGN IS THE POWER TO BUILD OUR EXPERIENCE, HOW CAN WE DO THAT WITH APPLIED SUSTAINABLE TECHNOLOGIES AND MAKE THEM INTEGRAL TO THAT EXPERIENCE THROUGH DESIGN? ELECTRONIC WASTE IS INCREASING WITH MORE TECHNOLOGIES. THIS PROJECT IS ABLE TO LESSEN THE AMOUNT OF WASTE IN RECYCLING COILS AND MAGNETS FROM ELECTROMAGNETIC GENERATORS FOUND IN SMALL ANDWASTE LARGE APPLIANCES AND ACTUATOR ELECTRONIC IS INCREASING WITH ASSEMBLIES FROM COMPUTER HARD DRIVES MORE TECHNOLOGIES. THIS PROJECT IS

ABLE TO LESSEN THE AMOUNT OF WASTE IN RECYCLING COILS AND MAGNETS FROM ELECTROMAGNETIC GENERATORS FOUND IN SMALL AND LARGE APPLIANCES AND ACTUATOR ASSEMBLIES FROM COMPUTER HARD DRIVES

MOVEMENT, THE MAGNETS MOVE INSIDE THE COILS GENERATING ELECTRICITY

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IDEALLY, A SINGLE STRING WOULD BE ABLE TO BE STRUNG WITHIN THE FRAME ALLOWING FOR SIMPLE REPAIR AND INEXPENSIVE MAINTENANCE. MINIMAL PARTS ALLOWS THIS TECHNOLOGY TO BE DEPLOYED COMMONLY AND IDEALLY, A SINGLE STRING WOULD BE ISSTRUNG CURRENTLY INTRODUCED ABLE TO BE WITHINBEING THE FRAME TOFOR THIRD-WORLD COUNTRIES ALLOWING SIMPLE REPAIR AND

INEXPENSIVE MAINTENANCE. MINIMAL PARTS ALLOWS THIS TECHNOLOGY TO BE DEPLOYED COMMONLY AND IS CURRENTLY BEING INTRODUCED TO THIRD-WORLD COUNTRIES

LOCATIONS OF MAGNETS (ADHERED TO THE CONNECTION POINT TO OTHER UNITS TAPE) SITUATED BETWEEN COPPER MAGNETIC WIRE COILS. THROUGH THE WIND HOLLOW RIGID FRAME MOVEMENT, THE MAGNETS MOVE INSIDE THE COILS GENERATING ELECTRICITY RECYCLED VHS TAPE STRUNG THROUGH FRAME CONNECTION POINT TO OTHER UNITS MOVEMENT HOLLOW RIGID FRAMEOF WIND THROUGH THE UNIT

RECYCLED VHS TAPE STRUNG THROUGH FRAME

BUILDING

MOVEMENT OF WIND THROUGH THE UNIT

BUILDING

SUPPORT TO BRACE ITSELF AGAINST THE BUILDING ADDING GREATER STABILITY CONNECTION POINT TO OTHER UNITS

OWER STEM WIND OLOGY FROM WER MENT EM

ND OGY OM ENT

THE THREE-DIMENSIONALITY OF THE UNIT ALLOWS FOR GREATER COLLECTION POINTS. ADDITIONALLY, THE UNITS ARE DESIGNED TO COMBINE TO COVER MORE SURFACE A PLUS FROM OF LARGE THE AREA, THREE-DIMENSIONALITY VERTICAL FACADES OF A CITY THE UNIT ALLOWS FOR GREATER COLLECTION POINTS. ADDITIONALLY, THE UNITS ARE DESIGNED TO COMBINE TO COVER MORE SURFACE LOCATIONS OF MAGNETS (ADHERED TO THE TAPE) SITUATED AREA, A PLUS FROM LARGEBETWEEN COPPER MAGNETICA WIRECITY COILS. THROUGH THE WIND VERTICAL FACADES OF

SUPPORT TO BRACE ITSELF AGAINST THE BUILDING ADDING GREATER STABILITY CONNECTION POINT TO OTHER UNITS

BOLT CONNECTIONS FOR FASTENING ON TO EXISTING STRUCTURES

BUILDING

SECTION 1

SECTION 1

SECTION 2

3D PRINTING ALLOWS FOR THE FRAME TO BE PRINTED INCORPORATING THE HOUSING AND ATTACHMENTS FOR THE MAGNETS, MAKING FOR LESS PARTS IN MAINTENANCE

LARGE WIND BOLT CONNECTIONS FOR FASTENING ON TOUNLIKE EXISTING STRUCTURES

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3D PRINTING ALLOWS FOR THE FRAME TO BE PRINTED INCORPORATING THE HOUSING AND ATTACHMENTS FOR THE MAGNETS, MAKING FOR LESS PARTS IN MAINTENANCE

TURBINES, THIS TECHNOLOGYWORKSATASMALLER SCALE AND WITH WIND FORCES FROM MULTIPLE DIRECTIONS, MAKING IT APPLICABLE TO EXISTING URBAN INFRASTRUCTURES

UNLIKE LARGE WIND TURBINES, THIS TECHNOLOGYWORKSATASMALLER SCALE AND WITH WIND FORCES FROM MULTIPLE DIRECTIONS, MAKING IT APPLICABLE TO EXISTING URBAN INFRASTRUCTURES

FRONT THIS PROJECT WAS RECENTLY AWARDED FUNDING FROM PRATT’S FACULTY DEVELOPMENT FUND FOR 2012-2013. ALTHOUGH THE ACCOMPANYING

BUILDING SECTION 2

WIND COMING FROM MULTIPLE DIRECTIONS AS IS THE CASE IN A CITY ENVIRONMENT

BOLT CONN SECTION 1

3D PRINTING ALLOWS FOR THE FRAME TO BE PRINTED INCORPORATING THE HOUSING AND ATTACHMENTS FOR THE MAGNETS, MAKING FOR LESS PARTS IN MAINTENANCE

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SIDE 1

FRONT

wind simulation tests on designed array

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WIND SIMULATION STUDIES

THIS PROJECT WAS RECENTLY AWARDED FUN FROM PRATT’S FACULTY DEVELOPMENT F FOR 2012-2013. ALTHOUGH THE ACCOMPAN MODELS DO NOT FUNCTION, A WOR SCALED MODEL IS IN DEVELOPMENT TO THE TECHNOLOGY AND ITS FEASIBILITY VIABLE SUSTAINABLE SOLUTION FOR G TECHNOLOGIES AND MAKING THEM M ATTRACTIVE THROUGH DESIGN.

This system used rare earth magnets situated between copper magnetic wire coils affixed to the belt. Wind vibrating over the belt caused the magnets to move inside the coils, generating electricity. This proved problematic, as the magnets were too attractive towards each other and would adhere together, ending opportunity of electricity THESE IMAGES SHOW THE BEGINNINGS PROTOTYPE CURRENTLY BEING DEVELOPED generation because of the precision required in placement of the magnets.

TESTED PROF.of MARGARET Moving forward for different solutions, the use of piezoelectricity is a more promising method wind KIRK capture WIND SIMULATION STUDIES VISITING ASSISTANT PROFESSOR SCHOOL OF INTERIOR DESIGN and generation.

3_ PIEZOELECTRICITY In 1880, it was found that quartz crystals changed shape in an electrical field and generated electrical charge when mechanical stress was applied. Current piezoelectricity depends on the deflection of the electrical dipole - generation of electricity or electric polarity is produced when dielectic crystals are pressed or squeezed.

“At the molecular level, the dipoles formed by the positive and negative ions cancel each other due to the symmetry of the crystal structure, and an electric field is not observed. When stressed, the crystal deforms, symmetry is lost, and a net dipole moment is created. This dipole moment forms an electric field across the crystal. In this manner, the materials generate an electrical charge that is proportional to the pressure applied.” 3 3.1_ TYPES Piezoelectric devices can be categorizes as follows: piezo sensors, piezo actuators, transducers, and generators.

• Sensors convert physical stimulus into an electrical signal.

• Actuators convert an electrical signal into a precisely controlled physical displacement • Transducers convert electrical energy into vibrational mechanical energy useful for performing tasks. A transducer can both generate an ultrasound signal from electrical energy and convert incoming sound into an electrical signal.

• Piezoelectric generators generate voltages sufficient to spark across an electrode gap, and are small, simple, and can be used for storage in batteries. They have been used in ignitors in fuel lighters, doorbells, health monitoring applications, and even in kinetic floors.

Because of the piezoelectric generators’ electricity storage properties, this piezoelectric device will be used for this application of secondary building facades. The deflection of these devices on a film are intended for use to deflect under wind pressure produced in cities.

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Karki, James. Signal Conditioning Piezoelectric Sensors. Texas Instruments Incorporated, Mixed Signal Products, 2000.

“Applications of Piezoelectric Ceramics.” Piezo Applications | Piezoelectric Generators, Sensors, Transducers, APC International, Ltd., 2016, www. americanpiezo.com/knowledge-center/piezo-theory/applications.html.

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3.2_ PRODUCT SELECTION The research team determined that the following piezo sensor would prove testable, being able to hook the piezo leads from the film strip to test energy output, helping to determine the viability of piezoelectic generators.

LDT1-028K PIEZO SENSOR 5 w/ Leads Attached SPECIFICATIONS • Piezoelectric Polymer • SPECIFICATIONS Multi-purpose •  Vibration Sensing Piezoelectric Polymer •  Impact Sensing Multi-purpose •  Laminated Vibration Sensing Impact Sensing •  Dual Wire Lead Attached  

DIMENSIONS Dimensions in mm [inches]

Laminated Dual Wire Lead Attached

The LDT1-028K is a multi-purpose, piezoelectric sensor for detecting physical phenomena such as vibration or impact. The piezo film to a sheet of polyester (Mylar), Theelement LDT1-028Kisislaminate a multi-purpose, piezoelectric sensor for detecting physical phenomena as when forces are and produces a useable electrical signalsuch output vibration to or impact.

The piezo film element is laminate a attached to the applied the sensing area.

The dual wire to lead sheet of polyester (Mylar), and produces a useable sensor to aapplied circuittoorthemonitoring device electricalallows signal easy output connection when forces are tosensing process the signal. area.

The dual wire lead attached to the sensor allows easy connection to a circuit or monitoring device to process the signal.

FEATURES

• Minimum Impedance: 1 MΩ • FEATURES Preferred Impedance: 10 MΩ and higher MinimumVoltage: Impedance: MΩ •  Output 101 mV-100 V depending on force and circuit  impedance Preferred Impedance: 10 MΩ and higher  Output Voltage: 10 mV-100 V depending on force and • Storage Temperature: -40°C to +70°C [-40°F to 60°F] circuit impedance Storage Temperature: -40°C to0°C +70°C 60°F] to 160°F] •  Operating Temperature: to [-40°F +70°Cto [32°F 

Operating Temperature: 0°C to +70°C [32°F to 160°F]

APPLICATIONS • APPLICATIONS Sensing direct contact force Sensing direct contact •  Recording time of force an event  Recording time of an event • Measuring impact related events  Counting number of impact events •  Sensing using a cantilevered beam Measuringvibration impact related events •  Wakeup switchusing a cantilevered beam Sensing vibration Wakeup detection switch •  Motion 

Motion detection

4_ INITIAL EXPERIMENTATION After acquiring a number of small piezoelectric sensor strips, their output was measured in a set of initial experiments using an oscilloscope to determine potential energy output from wind energy in a fan.

4.1_ INITIAL WIND TESTS SENSOR SOLUTIONS /// LDT1-028K Piezo Sensor Rev 1

07/2017

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The sensor based was stabilized, allowing air flow to react with the film strip. The leads connected to the base of the strip were attached to an oscilloscope to gain an energy reading. The fan was directed at the sensor, blowing it at differing speeds to produce the reading.

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TE Connectivity. “Piezoelectric Polymer Vibration Sensor.” United States. 2018.

oscilloscope readings from singular piezoelectric sensor under wind force These oscilloscope readings describe the best results from the experimentation, showing extremely low energy output from the input wind, resonating at about 10mV. The typical output voltage of the sensor, as found in the product spec sheet, is 10 mV- 100 V. The sensors were producing the minumum amount of energy output from incoming wind energy. These tests also showed that the sensors produce more energy with sudden velocity, rather than acceleration. An immediate force would produce a large deflection, and thus more mV. Constant airflow produced much less energy than did an abrupt wind force.

This experiment was repeated several times with minimally or nonexistent improvement in results. Because this was the first test in energy output from a piezoelectric sensor at all, other options for how to increase output came into question, while still following a biomimectic model.

4.2_ INITIAL WATER TESTS As biomimicry is the the point of departure in this venture, looking to natural systems with designed water collection became a brief subject of interest. Water is another force existent in high density urban areas, and could be used in conjunction with wind to maximize the force hitting the piezoelectric device. In the initial experiments, it was found that piezoelectric generators produce electricity upon deformation, and the thought that water could be used as another potential large force (produced due to gravity, i.e. as it falls). If water was concentrated to a point - in this case, to the piezo - then controlled distribution could cause a large deformation due to a large force. Desert plant biomimicry was used as inspiration for possible formal means of directing water to a point onto a film piezoelectric generator.

4.2.1.1_ CACTI WATER COLLECTION

The cactus can additionally serve as a model for water accumulation. Water condensing on a cactus surface collects on its spikes, turning water droplets into even larger drops to maximize collection. Fog nets featuring cactus-inspired conical structures increase surface area available for droplet interception and help facilitate efficient droplet coalescence and movement, resulting in a greater amount of water collected.

fog net inspired by cacti water collection6

Brown, Philip S., and Bharat Bhushan. “Bioinspired Materials for Water Supply and Management: Water Collection, Water Purification and Separation of Water from Oil.� Philosophical Transactions of the Royal Society of London A: Mathematical, Physical and Engineering Sciences, The Royal Society, 6 Aug. 2016, rsta.royalsocietypublishing.org/content/374/2073/20160135.

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4.2.1.2_ LIZARD WATER COLLECTION

The Thorny Devil is a desert lizard known for harvesting and directing water with its skin, composed of a series of mounds and valleys which effectively channel water to its mouth via capillary action. It expends no extra energy to transfer water to its mouth - the small grooves are enough to defy gravity as it stands in a pool of water to collect water.

microscopic view of valleys in thorny devil skin7

4.2.2_ TEST RESULTS

To test the capabilities of water-based deformation, our team conducted simple experiments dropping water onto film piezoelectric generators. The oscilloscope readings resulting from the waterbased tests produced readings that showed little to no reading upon simulation of water (testing a simulated form of precipitation) acting as a force on the piezoelectric devices. While this digression was of interest, testing proved that using water in this application was not a productive enough means of energy generation to continue with its experimentation.

testing the force of falling water on piezoelectric sensors

Refocusing again on wind, as with Professor Kirk’s original intentions, serve as the propellant in futher investigations.

oscilloscope readings from singular piezoelectric sensor under direct point water pressure

At this point, Raul and Christian were unable to continue on the research team and Liam Chaffey assumed their roles.

7 Woolley-Barker, PhD. Tamsin. “The Biomimicry Manual: What Can a Thorny Devil Teach Us About Water Harvesting?” Inhabitat Green Design Innovation Architecture Green Building, Inhabitat, 1 Sept. 2013, inhabitat.com/the-biomimicry-manual-what-can-a-thorny-devil-teach-us-aboutwater-harvesting/

5_ ARRAY FORMAL GENERATION After determining that wind proved the most effective force for energy capture, exploration of piezoelectric device arragement came into question. These films were acquired in the hopes of placing many piezoelectric generators into a housing module, which could be arrayed across an existing facade. Looking to the cacti model for turbulence creation, how to affix the generators into a designed housing array came into came into question. Emulating the directive nature of cacti pleats and spines, several conical models were designed to direct air to a point (where the piezoelectric generators would be placed). They were designed using Rhino, a 3D design application software, and assesed using a computational fluid dynamics (CFD) software, which is used to analyze problems that involve fluid flows.

5.1_ CONICAL ARRAY The first set of iterations of our designed array involved a series of square-based cones, ideally holding the piezos inside their shells. The first model (1) included an identical rectangular array of closed cones. The second model (2) halved these cones to expose the interior shell of the cone material and piezo directly to oncoming wind. The third model (3) gradually increased the height of otherwise identical closed square-based cones.

The fourth model (4) involved openings at the end of the holes to eliminate backpressure, or pressure opposed to the desired flow in confined places.

(1)

(3)

(2)

(4)

After virtual CFD analysis, the final model proved most successful. The cones produced more turbulence after expelling incoming air than within the cone. This model did create high velocity situations, which would be desirable for piezoelectric deflection.

first set of iterations of square-based cone array

This array also contanined holes inbetween the cones, which allowed additional air to pass through.

The absence of these would result in large area of high pressure, disinclining movement of air into the array.

CFD analysis of concial array to contain piezogenerators

5.2_ GRID ARRAY The previous CFD tests showed success with turbulence creation behind the array, so the next iteration experimented with the addition of a backplate. The CFD tests show on the right show a possible array in section, comparing velocity and pressure with and without a backplate.

The addition of this plate would direct wind back into the system, rather than letting the built-up wind dissipate unused. The third iteration (bottom, left) shows air recirculating back into the array, also evidenced in the pressure diagram on the right.

With this knowledge, how to array the actual piezos in this system is next in experimentation, as well as if there is an implementation to catalyze air capture in the individual devices.

left_ measured velocity, before and after the addition of a back plate. the third image places the piezo housing further from the plate. above_ measured pressure before and after addition of the backplate.

6_ DEVICE FORMAL GENERATION Because the films do not have a significant inherent stiffness or mass, we conducted an experiment testing how an increase in both elements would affect energy collection. The piezoelectric device was cast into a semirigid urethane casting resin, which provided the piezoelectric strip with resistance and resiliency. The creation of a mold allowed the same shape to be tested in multiple resins differing in elasticity and stiffness.

Because the small film lacked sufficient surface area to acquire productive results, another piezoelectric sensor was acquired to test. It had the same properties as the small films used, but increased surface area. It measures 6” x 1”, and allowed for a supplemented test to be performed inside the cast.

The scheme for casting included CNC milling a 3D-modeled cast shape out of ultra light medium density fiberboard, which was a viable option for its sensitivity to small router bits and ability to smooth when sanded.

The cast form itself again evolved from biomimectic forms.

6.1.1_ MOLD FORMING_ SEED The first CNC mold proposal was derived from dandelions, which rely on wind for seed dispersion.

They are arraged to allow multi-directional wind capture. By modeling the form of a large base which thins in length but is topped by a larger mass, the piezos would be available to maximum deflection by the maxmimum amount of wind vectors. dandelion seeds8 & the first CNC cast form proposal

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“Dandelion Seeds.” Science Learning Hub, The University of Waikato, 2018, www.sciencelearn.org.nz/images/92-dandelion-seeds.

6.1.2_ MOLD FORMING_ CILIA The team later determined that the larger mass on the petal mold would actually prove detrimental, as its weight would likely be too high to be affected by lower wind velocities. A CNC mold based on cellular cilia was designed instead. Cilia are hairlike protuberances on the exterior of eukaryotic cells and typically wave in pulsating motions. Their shape and purpose served as an effective model for our purposes.

The mold included a larger cylindrical voids at either end. The smaller void was intended for filling the mold with soft resin. The larger void was sized to the electircal cables which housed the piezoelectric generator wires back to the oscilloscpe. The 6 intermittent holes on either side of the mold were intended as match points to screw the mold together with.

top_

top_ cilia on a eukaryotic cell9 left_ the cilia-based mold in its digital form before being modeled lower_ preparing a mdf fiberboard base within the wind tunnel bottom_ the cast resin/ piezoelectric generator model attached to the mdf fiberboard base

6.2_ MODEL TESTING The final model included a 3D printed base and 3D printed topping cast into semi-rigid urethane resin (seen in orange filament in the bottom left image).

The team gained access to Cal Poly’s areospace wind tunnel to conduct the experiment. A large, solid base was constructed from mdf fiberboard to house the resin/3D printed model and mimic the surface of a building. We then screwed the model onto the mdf base, and applied various wind velocities to the model.

The wind velocity began at 10mph, and was increased by increments of 10mph. The model was stiff until reaching about 30mph, and resulted in negligible electrical output even after reaching 70mph. These higher wind speeds are not common enough for this resin model to prove effective at the more frequent lower wind velocities which affect tall structures. The team anticipates the necessity of trying different flexible resins based on elasticity and stiffness using the same form.

This concludes my report. Further iterations of the mold configurations will resume in future research.

9 Aryal, Sagar. “Cilia and Flagella- Definition, Structure, Functions and Diagram.� Microbe Notes, Generate Press, 8 Feb. 2020, microbenotes.com/ cilia-and-flagella-structure-and-functions/