High Energy Density Picoliter Zn-Air Batteries for Colloidal Robots and State Machines

Abstract

The recent interest in microscopic autonomous systems, including microrobots, colloidal state machines and smart dust has created a need for microscale energy storage and harvesting. However, macroscopic materials for energy storage have noted incompatibilities with micro-fabrication techniques, creating significant challenges to realizing microscale energy systems. Herein, we photolithographically pattern a microscale Zn/Pt/SU-8 system to generate the highest energy density microbattery at the picoliter (10^-12 L) scale. The device scavenges ambient or solution dissolved oxygen for a Zn oxidation reaction, achieving an energy density ranging from 760 to 1070 Wh L-1 at scales below 100 μm lateral and 2 μm thickness in size. More than 10,000 devices per wafer can be released into solution as functional colloids with energy stored onboard. Within a volume of only 2 pL each, these microbatteries can deliver open circuit voltages of 1.16 V with total energies ranging from 5.5 ± 0.3 to 7.7 ± 1.0 μJ and a maximum power near 2.7 nW. We demonstrate that such systems can reliably power a micron-sized memristor circuit, providing access to non-volatile memory. We also cycle power to drive the reversible bending of microscale bimorph actuators at 0.05 Hz for mechanical functions of colloidal robots. Additional capabilities such as powering two distinct nanosensor types and a clock circuit are also demonstrated. The high energy density, low volume and simple configuration promise the mass fabrication and adoption of such picoliter Zn-air batteries for micron-scale, colloidal robotics with autonomous functions.

Colloidal State Machines as Smart Tracers for Chemical Reactor Analysis

“…The size constraints will put a certain cap on the capabilities of each smart tracer particle, such as the number of electronic components and the amount of energy it can store. [ 117 ] Therefore, it is of great importance for design to figure out how the capabilities of each particle affect the overall fitting. In particular, we focus on the effects of data storage space, as it is often linearly correlated with the physical size of particles.…”

“…But we believe those challenges can be solved in the coming years with the advancement of photolithography techniques. Key components such as sensors, [63,67,68] memory devices, [66,72] and clock circuits [72,117] have already been demonstrated individually on other microrobots. Reliable methods for releasing and collecting smart tracer particles are also needed to ensure a uniform sampling over the cross-sectional area of reactors.…”