Smart Multichain USDC Payment Scheduler

Welcome to the Smart Multichain USDC Payment Scheduler, a decentralized application (dApp) designed to automate USDC payments across multiple blockchain testnets (Ethereum Sepolia, Polygon Mumbai, and Arbitrum Sepolia). This project, built for the [Hackathon Name] 2025, integrates the LI.FI SDK for fee optimization, MetaMask SDK for wallet connectivity, and Chainlink Automation for future scalability. The modern, professional UI leverages React and Tailwind CSS, offering a seamless user experience.

Table of Contents

• Overview

• Features

• Architecture

• Installation

• Usage

• Demo

• Technical Details

• Acknowledgments

Overview

The Smart Multichain USDC Payment Scheduler addresses the challenge of managing recurring payments across blockchains. Users can schedule USDC payments with customizable intervals and execute them manually (with Chainlink Automation planned for production). The dApp optimizes transaction fees using the LI.FI SDK and supports multichain deployment, making it ideal for use cases like subscriptions, payroll, or cross-border remittances.
This project was developed as part of a hackathon submission, bonuses for LI.FI ($2,000) and MetaMask ($2,000) integrations. The code is open-source, and the dApp is deployed at https://multichain-usdc-payment-scheduler.vercel.app.

Features

• Multichain Support: Deployed on Ethereum Sepolia, Polygon Mumbai, and Arbitrum Sepolia testnets.

• USDC Payment Scheduling: Schedule payments with custom amounts, recipients, and intervals.

• Fee Optimization: Uses LI.FI SDK to find the lowest-cost chain for transactions.

• Wallet Integration: Connects seamlessly with MetaMask via the MetaMask SDK.

• Transaction Signing:Transaction Signing: Users approve payment scheduling and execution transactions by MetaMask

• Network Switching: MetaMask facilitates switching between testnets

• Professional UI: Modern design with Tailwind CSS, featuring cards, gradients, and responsiveness.

• Multichain Support: It enables seamless fee calculations for USDC transfers across different testnets, aligning with the project's multichain design and ensuring cost-effective payment scheduling.by help of LI.FI SDK

• API Integration: The LI.FI SDK provides real-time quote data (e.g., gas costs in USD), integrated into the UI’s “Calculate Fees” feature, offering users transparent cost insights before transactions

• Chainlink Compatibility: Designed for future automation with Chainlink Automation.

• Real-Time Feedback: Displays payment status and estimated fees in the UI.

Architecture

The project follows a modular architecture combining frontend, smart contract, and deployment layers:

Architecture Diagram

+-----------------------------------------------------+|                   Frontend (dApp)                   || +-----------------------------------------------+  || | React + JSX                                   |  || | - UI: Tailwind CSS, Card-based Layout         |  || | - Libraries: Web3.js, MetaMask SDK, LI.FI SDK |  || +-----------------------------------------------+  ||                                                    |+-----------------------------------------------------+
          | (Interacts with Smart Contract via Web3)
          v+-----------------------------------------------------+|                Smart Contract Layer                || +-----------------------------------------------+  || | USDCPaymentScheduler.sol                      |  || | - Language: Solidity 0.8.28                   |  || | - Features: Payment Scheduling, Execution     |  || | - Dependencies: Chainlink Automation Interface|  || | - Deployed on: Sepolia, Mumbai, Arbitrum Sepolia |  || +-----------------------------------------------+  ||                                                    |+-----------------------------------------------------+
          | (Deployed using Hardhat)
          v+-----------------------------------------------------+|                  Deployment Layer                  || +-----------------------------------------------+  || | Hardhat                                       |  || | - Config: hardhat.config.js                   |  || | - RPCs: Alchemy (Sepolia, Mumbai, Arbitrum)   |  || | - Verification: Etherscan, Polygonscan, Arbiscan |  || | - Script: deploy-v2-contracts.js              |  || +-----------------------------------------------+  ||                                                    |+-----------------------------------------------------+

Explanation

• Frontend: Built with React and rendered via index.html. The UI uses Tailwind CSS for styling, with Web3.js for blockchain interaction, MetaMask SDK for wallet connectivity, and LI.FI SDK for fee optimization. It communicates with the smart contract via RPC calls.

• Smart Contract: The USDCPaymentScheduler.sol contract, written in Solidity, handles payment scheduling and execution. It integrates with the Chainlink AutomationCompatibleInterface for future automation and uses the IERC20 interface for USDC interactions.

• Deployment: Managed with Hardhat, using a custom deploy-v2-contracts.js script. RPC URLs (e.g., Alchemy) and API keys (e.g., Polygonscan) are configured via .env, with contracts verified on respective explorers.

Installation

To run this project locally, follow these steps:

Prerequisites

• Node.js (v16 or later)

• npm (comes with Node.js)

• MetaMask wallet with testnet funds (Sepolia ETH, Mumbai MATIC, Arbitrum Sepolia ETH)

• Alchemy accounts for RPC URLs (free tier)

Steps

1. Clone the Repository:

   git clone https://github.com/your-username/usdc-payment-scheduler.git
   cd usdc-payment-scheduler
   

2. Install Dependencies:

   npm install
   npm install --save-dev hardhat @nomicfoundation/hardhat-toolbox @chainlink/contracts dotenv
   

3. Configure Environment Variables:

   • Create a . file in the root directory:

     SEPOLIA_RPC_URL=https://eth-sepolia.g.alchemy.com/v2/your-alchemy-api-key
     MUMBAI_RPC_URL=https://polygon-mumbai.g.alchemy.com/v2/your-alchemy-api-key
     ARBITRUM_SEPOLIA_RPC_URL=https://arb-sepolia.g.alchemy.com/v2/your-alchemy-api-key
     PRIVATE_KEY=0xYourPrivateKey
     POLYGONSCAN_API_KEY=YourPolygonscanApiKey
     ARBISCAN_API_KEY=YourArbiscanApiKey
     ETHERSCAN_API_KEY=YourEtherscanApiKey
     LIFI_API_KEY=xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
     LIFI_INTEGRATOR_ID=xxxxxxxxx
     

   • Replace placeholders with your Alchemy API keys, MetaMask private key (testnet-only), and explorer API keys.

4. Set Up Hardhat:

   • Initialize Hardhat if not already done:

     npx hardhat init
     

   • Accept defaults for a JavaScript project and update hardhat.config.js with the provided configuration.

5. Install Serve (for UI):

   npm install -g serve
   

Usage

Deploying the Contract

1. Run the deployment script:

   npx hardhat run scripts/deploy-v2-contracts.js
   

2. Note the deployed contract addresses for Sepolia, Mumbai, and Arbitrum Sepolia.

3. Update the contractAddresses object in index.html with these addresses.

Running the dApp

1. Start the local server:

   serve
   

2. Open http://localhost:3000 in a browser.

3. Connect MetaMask to a testnet (e.g., Sepolia), fund it with testnet tokens, and interact with the UI:

   • Schedule a payment (e.g., 10 USDC, 60-second interval).

   • Execute the payment after the interval and verify on the explorer.

Testing

• Test responsiveness by resizing the browser or using Chrome DevTools.

• Verify fee optimization by scheduling payments on different chains.

• Check MetaMask popups for transaction approvals.

Demo

A live demo is available at https://multichain-usdc-payment-scheduler.vercel.app. The video pitch (3–5 minutes) includes:

• Connecting MetaMask and scheduling a 10 USDC payment.

• Executing the payment after 60 seconds.

• Showcasing the modern UI (navigation, cards, gradients).

• Highlighting LI.FI fee optimization and Chainlink compatibility.

Technical Details

• Frontend: React, Tailwind CSS, Web3.js, MetaMask SDK, LI.FI SDK.

• Smart Contract: Solidity 0.8.28, Chainlink Automation interface.

• Deployment: Hardhat, Alchemy RPCs, Etherscan/Polygonscan/Arbiscan verification.

• Dependencies: @chainlink/contracts, dotenv.

• Contract Addresses: Update index.html with deployed addresses (e.g., Sepolia: 0xYourSepoliaAddress).

Acknowledgments

• LI.FI: For the SDK and $2,000 bonus.

• MetaMask: For the SDK and $2,000 bonus.

• Chainlink: For Automation inspiration.

• Alchemy: For reliable RPC endpoints.