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  • Payment Address: 0xF9310880F753a2327146dD19EC2207E6bA482A19 (USDC)
  • Level: 3

Project Overview πŸ“„β€‹


  • Polkadart is a Dart library that provides a clean wrapper around all the methods exposed by a Polkadot/Substrate network client and defines all the types exposed by a node. It's an equivalent to polkadot-api written in Dart language.

  • Development of a library that allows users to connect to Polkadot/Substrate’s nodes on Flutter platform.

  • Our team is developing a ranking-based voting system based on the Substrate's based blockchain and for that, we need to create the Dart-substrate library. Today, there are multiple mobile applications built on Flutter and, until now, there is no possibility to connect to Substrate's nodes.

Project Details​

  • An overview of the technology stack to be used:
This library will be written purely in Dart technology from scratch.
  • Documentation of core components, protocols, architecture, etc. to be deployed:
We will follow Polkadot specifications and, as a license for PolkaDart library, we will use Apache 2.0.
  • What your project is not or will not provide or implement:
This project will not support legacy metadata protocols, such as metadata v9, v10, v11 and v12. Polkadart will not implement any front-end, since it is going to allow developers to use Dart to connect to the Substrate based network.
  • This is a place for you to manage expectations and to clarify any limitations that might not be obvious:
Polkadart is similar to the project "" but for Dart, instead of JavaScript.

Ecosystem Fit​

  • Where and how does your project fit into the ecosystem? Our project is going to allow developers to use Dart/Flutter to connect to the Substrate-based network.
  • Who is your target audience (parachain/dapp/wallet/UI developers, designers, your own user base, some dapp's userbase, yourself)? Our target audience is the mobile app developer's community.
  • What need(s) does your project meet? Polkadart enlarges the range of tools compatible with Polkadot/Substrate, therefore expanding its usability.
  • Are there any other projects similar to yours in the Substrate / Polkadot / Kusama ecosystem? Pocket 4 Polkadot-Dart: Polkaj:
    • If so, how is your project different? Pocket4 was similar to PolkaDart but it was discontinued for lack of progress and Polkaj is related to Java.

Team πŸ‘₯​

Team members​

  • Lohann Ferreira, Lead Blockchain Architect
  • Leonardo Custodio, Blockchain Engineer
  • Hanna Coutinho, iOS Developer
  • Kawaljeet Singh, Flutter Developer
  • Luiza Adena Engers, Product Manager
  • Fabio Binder, Blockchain Engineer
  • Gabriel Okura, Flutter Developer
  • Bruno Pastre, Senior Flutter Developer


  • Registered Address: Rua Monsenhor Celso, 154, Centro, Curitiba-ParanΓ‘, Brasil.
  • Registered Legal Entity: Jurimetric Tecnologia Ltda.

Team's experience​

Lohann Ferreira

Lohann have a deep understanding of Polkadot/Substrate stack amongst other blockchain technologies. Previously worked at First Foundry as Senior Software Engineer. Founder and lead engineer at Jurimetric. Co-founder of Veever, which through the combination of beacons, a web platform, and a mobile app aims to assist people with visual impairment to easily get around and interact with the urban environment. He is focused on solving big problems with simple ambitious solutions.

Leonardo Custodio

Leonardo has being working with Polkadot/Substrate stack for the past 14 months. At his current position he makes SDKs that allows game developers to work easily with substrate based chain. Before that he was the Lead Mobile Developer of Inovatso where he has created multiple applications for the general public like picPics and other entreprise applications using Flutter.

FΓ‘bio Binder

Binder has over 25 years of experience with development. Currently, he is the Program Head at PUCPR of the Apple Developer Academy. He was recognized as an Apple Distinguished Educator in 2019, for doing amazing things with Apple technology in and out of the classroom. He joined Jurimetric because he wants to be a part of the Web 3 movement as a hands-on developer of blockchain technology.

Hanna Coutinho

Currently working as an iOS developer at Snowman Labs. She's a scholarship student at Apple Developer Academy and is pursuing a Bachelor's Degree in Computer Information Systems, at PUCPR (ParanΓ‘, Brazil). Hanna's biggest dream is to work at a tech company where she can bring positive social impacts to minorities. A fun fact about her, she's also a Lawyer, but she found a true passion in technology, programming, and design.

Kawaljeet Singh

Before starting to work as a full-time flutter developer at Rankanizer, Kawal was working as a freelance Flutter Developer at Inovatso and on other projects. In his free time, he loves to create open-source tools and plugins in dart to help the Flutter community. He is a blockchain enthusiast and is super dedicated to learning and bringing ideas to life.

Luiza Adena

Luiza is Jurimetric's Product Manager. She founded a legal tech called Arbi-ON and has experience with problem-solving through creative thinking. Luiza aims to make society more just and she believes Rankanizer has the potential to empower people equally.

Gabriel Okura

Gabriel is currently working as a mobile and backend developer at Hype Empreendimentos, and for the past year and a half, he has been having experience building apps in Dart with the Flutter framework. Previously worked with mobile game development at Opala Studios. He is excited about the opportunity to work on Rankanizer and to help build the PolkaDart library to increase his experience with blockchain technology.

Bruno Pastre Bruno is an iOS specialized Software Engineer who has consulted for large tech companies like Coinbase and Wish. He is fascinated about writing scalable, testable and maintainable code and has been working on that for the past four years. He's a Apple Developer Academy alumni, performing both as a student and a Junior Mentor, There, he had the opportunity to share his knowledge with the next generation of iOS developers and empower them to develop themselfs.

Team Code Repos​

Team LinkedIn Profiles (if available)​

Development Status πŸ“–β€‹

Out of the necessity of having a a library / sdk to use substrate chains in our other planned apps. We will start the development of Polkadart in the Grant's program. The repository that will be used during the development is We intend to have it open-source since the beginning and all code will be added through pull-requests.

We decided to divide this project into three milestones. The first one is building the codec and metadata part. Since without this all data would have to be mocked and tested using third-party tools as everything is encoded in the substrate eco-system.

After we are able to encode/decode data from primitive types and metadata's of any chain. We are going to proceed with the connectivity part. Where we will implement the interfaces necessary for communicating with the nodes through RPC.

Finally the last step will be the crypto and utils part where we will have the utilities necessary for signing transactions. After these three milestones are completed we shall have a fully featured library that will enable people in the Dart/Flutter ecosystem to communicate with any substrate based node, sign transactions, encode and decode data. Making it possible for example for people to develop flutter applications for Polkadot using native libraries.

Development Roadmap πŸ”©β€‹

Described above.


  • Total Estimated Duration: 7 months.
  • Full-Time Equivalent (FTE): 4.
  • Total Costs: 50,000 USD.

Milestone 1 —​

  • Estimated duration: 4 months.
  • FTE: 4.
  • Costs: 20,000 USD.
0a.LicenseApache 2.0
0b.DocumentationWe will provide markdown documentation of how to install and use the API.
0c.Testing GuideWe will provide sample scripts on how to use it.
0d.DockerWe will provide a Dockerfile(s) that can be used to test the PoC.
1a.Scale CodecFirst we will port the functionalities of scale codec to Dart. This way developers can decode and encode data from substrate.
1b.MetadataThen we will add the metadata parser so it can decode/encode the data by looking at the metadata. Important to note that we do not inteed to support legacy versions
1c.TestsUnit tests for deliverables above

Milestone 2 —​

  • Estimated duration: 1 month.
  • FTE: 4.
  • Costs: 15,000 USD.
0a.LicenseApache 2.0
0b.DocumentationWe will provide markdown documentation of how to install and use the API.
0c.Testing GuideWe will provide sample scripts on how to use it.
0d.DockerWe will provide a Dockerfile(s) that can be used to test the PoC.
2a.RPCWe will create the interfaces to use and connect to the node through RPC.
2b.WebsocketsWe will add websockets support to the above.
2e.TestsUnit tests for deliverables above

Milestone 3 —​

  • Estimated duration: 2 months.
  • FTE: 4.
  • Costs: 15,000 USD.
0a.LicenseApache 2.0
0b.DocumentationWe will provide markdown documentation of how to install and use the API.
0c.Testing GuideWe will provide sample scripts on how to use it.
0d.DockerWe will provide a Dockerfile(s) that can be used to test the PoC.
0e.Article/WorkshopWe will publish an example flutter project using the library to explain what was done and how to use it.
3a.KeyringWe will port the keyring management
3d.CryptoWe will add the utilities needed for signing transactions
3e.TestsUnit tests for deliverables above
3f.Pub.devPublish to for V1.0.0

Future Plans​

Until now we are bootstrapping, but we intend to continue to support the project with W3F Grant's help.

Our intention is to make the library available to whoever has an interest in using it. We need it to build Rankanizer, the next-generation app for enabling multiple-choice anonymous voting. Rankanizer will be a transparent and decentralized voting software built on blockchain technology.

Additional Information βž•β€‹

How did you hear about the Grants Program?

Lohann was informed about the Grants Program by personal recommendation.

πŸ’Ύ Work you have already done.

Lohann's previous work: \ Forte \ Rally \ Efinity \ Collectiba

Binder's previous work: \ Software project: Cluster - Social Impact Platform. Project Manager, Software Architect. \ Award: Apple Distinguished Educator 2019 \ PHD Thesis \ StackOverflow: 12.000+ points (top 3% overall) \ Personal Researcher Profile on Scopus

Kawal's previous work: \ AnimatedText \ Protect \ Tenor \ Excel