[Paper Review] An Insect-scale Untethered Laser-powered Jumping Microrobot

Palak Bhushan, Claire J. Tomlin|arXiv (Cornell University)|Aug 8, 2019

Biomimetic flight and propulsion mechanisms9 references4 citations

TL;DR

This paper presents an insect-scale, untethered laser-powered jumping microrobot weighing 75 mg and measuring 17 mm × 6 mm × 14 mm. It uses onboard photovoltaic cells to harvest infrared laser energy, enabling repeated jumps of 8 mm in height via a single electromagnetic actuator that loads and releases a spring mechanism passively using magnetic latching, achieving 6 jumps per minute with no external tethering.

ABSTRACT

We present the design of an insect-sized jumping microrobot measuring 17mm$ imes$6mm$ imes$14mm and weighing 75 milligrams. The microrobot consumes 6.4mW of power to jump up by 8mm in height. The tethered version of the robot can jump 6 times per minute each time landing perfectly on its feet. The untethered version of the robot is powered using onboard photovoltaic cells illuminated by an external infrared laser source. It is, to the best of our knowledge, the lightest untethered jumping microrobot with onboard power source that has been reported yet.

Motivation & Objective

• Develop a fully untethered, insect-scale microrobot capable of repeated jumping locomotion without external power cables.
• Overcome the limitations of prior untethered jumpers that rely on single-use energy sources or require manual reloading.
• Enable sustained, autonomous jumping using onboard photovoltaic cells and a passive magnetic release mechanism.
• Achieve stable, repeatable jumping with minimal control complexity by using a single electromagnetic actuator for spring loading and passive release.
• Demonstrate feasibility of laser-powered operation in a microrobot with minimal onboard electronics and low power consumption (6.4 mW).

Proposed method

• The microrobot uses a planar stainless steel spring with a T-shaped aluminum stand and feet to store mechanical energy via deflection.
• A 12.7 µm Kapton string connects the spring to a rotating shaft driven by a single electromagnetic coil, enabling spring loading through rotation.
• A magnetic latching mechanism with two anti-parallel N52 neodymium magnets (0.3 mm diameter, 0.5 mm height) provides passive release when the magnetic attraction is overcome.
• The electromagnetic actuator is designed to operate at low voltage (0.8 V) and current (8 mA), producing 17 µNm of torque via a 17 mm long moment arm.
• Onboard 1 mm × 1 mm infrared photovoltaic cells (976 nm wavelength) harvest laser energy to power the coil, with two cells connected in opposite polarity for bidirectional actuation.
• The system uses a square-wave voltage signal from an external source (for tethered tests) or laser illumination (for untethered operation) to drive the coil and cycle the jumping mechanism.

Experimental results

Research questions

• RQ1 Can a microrobot achieve repeated, untethered jumping using only onboard photovoltaic energy harvesting and a single electromagnetic actuator?
• RQ2 How can a passive magnetic latching mechanism enable reliable, repeatable spring release without additional control electronics?
• RQ3 What is the minimum power consumption required to achieve stable, repeatable jumping in an insect-scale microrobot?
• RQ4 Can laser-powered operation enable sustained jumping without tethering, and what are the limitations in jump height and repeatability?
• RQ5 How does the design minimize center-of-mass asymmetry to improve landing stability and enable consecutive jumps?

Key findings

• The microrobot achieved a jump height of 8 mm with a 75 mg mass, consuming only 6.4 mW of power in the tethered configuration.
• The untethered version successfully performed repeated jumps using laser-powered photovoltaic cells, with no measurable performance degradation from the added 3 mg of PV cell mass.
• The robot achieved a jumping rate of 6 jumps per minute in the tethered mode, limited by the spring loading speed, with mechanical power consumption in the tens of microwatts.
• The magnetic latching mechanism enabled reliable, passive release at 7.5 mN release force, allowing consistent jump initiation without additional control signals.
• The system demonstrated that low-voltage electromagnetic actuation (0.8 V, 8 mA) with direct PV power delivery eliminates the need for voltage conversion circuits.
• The robot exhibited anti-clockwise spin during flight, leading to instability upon landing; this was attributed to asymmetric center-of-mass and single-point spring support, suggesting design improvements for stability.