Wireless Foot-pedal: Phacoemulsification Surgery

I worked as a Product Development Intern at Aurolab, the manufacturing arm of the Aravind Eye Care System, where I led the design of a low-cost wireless surgical foot pedal for cataract phacoemulsification.

The goal was to create a surgeon-friendly, high-performance device tailored for resource-constrained hospitals across South Asia and Africa. I built the system from the ground up, combining an ergonomic enclosure with a custom PCB that enabled BLE-based wireless control and supported multi-axis input detection (vertical depression and lateral tilt) via Hall-effect sensors.

To align with Aravind’s mission of affordable, high-quality care, I optimized the electronics architecture—simplifying the sensor suite, consolidating the PCB, and selecting cost-effective components—to achieve a 51% reduction in overall electronics cost. After rigorous testing and refinement, I presented the final prototype to the Aurolab CEO and Division Head and received approval for full-scale production and deployment.

Aim: To design a surgical foot pedal with wireless capability and ergonomic comfort that meets industry standards while staying affordable for cost-sensitive markets.

Product Requirements

Microcontroller Selection: Nordic nRF52840

Selection Criteria

BLE 5.0+ wireless support
Sufficient GPIOs for sensors, switches, and LEDs
Low-power + battery compatibility
Proven use in medical or wearable devices
Strong SDK/dev tools for rapid development

Final Choice: Nordic nRF52840 DK

48 GPIOs, BLE 5.0, native USB, ARM Cortex-M4
Widely used in medical-grade wearables
Zephyr + Nordic SDK support

Cost-Optimized Sensor Selection

The foot pedal I designed uses a mix of digital switches and analog sensors.

The analog position sensor measures continuous pedal depression (vertical tilt) and side-to-side rocking (horizontal tilt)
The digital push switches handle discrete mode changes, while the analog sensor ensures smooth modulation of surgical functions.

Previously, Aurolab used a linear position sensor in the product, costing $281.28 USD per sensor. As this product is being developed for price-sensitive markets, I evaluated alternative sensors that provide the same functionality at a more optimal cost.

Selected Sensor:

Linear Hall-Effect Sensor:
- Contactless position sensor
- Measures the strength of a magnetic field
- Converts it into an analog voltage output
- Output varies linearly with distance

Meets our requirements:
- Contactless linear sensing
- High endurance (>10 million cycles)
- Analog + PWM output

Cost of this sensor: $137.89 USD (51% cost reduction)
Builds on the existing linear sensor mechanism in the Aurolab foot pedal
Ordered and tested the sensor quality, obtaining approval for product deployment

Wireless Foot Pedal - Systems Architecture Overview

Included Features:

Charging Circuit – Regulates external AC/DC power to safely charge the battery using an integrated charging IC.
3.7V Li-ion Battery Pack – the main DC power source
Battery Monitoring IC – Continuously measures battery voltage and current, reporting status to the MCU via I²C.
Power Converter – Converts 3.7V from the battery into stable 3.3V and 5V rails
Microcontroller (nRF52840) – Controls inputs & outputs
Programmable Buttons (4) – Allow user-defined functions for quick control.
Linear Position Sensors– Capture continuous analog motion
Wireless (BLE Communication) – Transmits pedal signals to the phaco console.
Phaco Console Back Panel PCB – Receives data transmission a