Machines made of soft materials bridge life sciences and engineering1. Advances in soft materials have led to skin-like sensors and muscle-like actuators for soft robots and wearable devices1-3. Flexible or stretchable counterparts of most key mechatronic components have been developed4,5, principally using fluidically driven systems6-8; other reported mechanisms include electrostatic9-12, stimuli-responsive gels13,14 and thermally responsive materials such as liquid metals15-17 and shape-memory polymers18. Despite the widespread use of fluidic actuation, there have been few soft counterparts of pumps or compressors, limiting the portability and autonomy of soft machines4,8. Here we describe a class of soft-matter bidirectional pumps based on charge-injection electrohydrodynamics19. These solid-state pumps are flexible, stretchable, modular, scalable, quiet and rapid. By integrating the pump into a glove, we demonstrate wearable active thermal management. Embedding the pump in an inflatable structure produces a self-contained fluidic 'muscle'. The stretchable pumps have potential uses in wearable laboratory-on-a-chip and microfluidic sensors, thermally active clothing and autonomous soft robots.

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Stretchable pumps for soft machines

Micropumps and biomedical applications – A review

Recent trends in mechanical micropumps and their applications: A review

We studied whether several agents, approved or undergoing trials in human glaucoma, were effective in preventing ganglion cell loss in the DBA/2J mouse. Adult DBA/2J mice were treated with timolol, pilocarpine, brimonidine, dorzolamide, or NMDA-receptor antagonist memantine. Surviving retinal ganglion cells of treated and control mice were retrogradely labeled with fluorogold and counted after whole mount preparation. In treated mice, only memantine and timolol had significant effects on retinal ganglion cell survival (P<0.0001, analysis of variance). Brimonidine was lethal to these mice, and these retinae were not analyzed further. The DBA/2J mouse represents a promising candidate for further experimentation in ocular hypertension.

Effects of Anti-glaucoma Medications on Gangion Cell Survival: The DBA/2J Mouse Model

This paper presents the design and development of a dual-chamber microchannel chip, coupled with an electromagnetic actuator for a bidirectional flow micropump system. A rapid prototyping technique is reported for the fabrication of the membrane sheet (a spin coater machine technique), microchannel chip (a photolithography technique) and controller system (a wet etching method to the circuit board), decreased development time by allowing correction and evaluation of the micropump to be made early in the process. To achieve a bidirectional flow, a dispersing depth was implemented between the microchannel chamber and inlet/outlet channel. From the numerical simulation and experimental analysis obtained, the micropump was capable for bidirectional flow application with the maximum volumetric flow rate of the fabricated micropump system at zero backpressure is 1.1254 ± 0.0658 μLs−1 (forward direction) and 1.1266 ± 0.0760 μLs−1 (reversed direction). The power consumption for the developed micropump system is 48.64 mW.

Electromagnetic actuation dual-chamber bidirectional flow micropump

Micropumps are finding more applications in biomedical fields. One application that holds great potential for micropumps is the treatment of glaucoma. Shunts are currently used in the treatment glaucoma. They lower intraocular pressure by passively increasing the outflow of aqueous humour from the anterior chamber in the eye. Nozzle/diffuser micropumps are an attractive alternative to shunts. They would provide both passive outflow and variable active outflow of aqueous humour as necessary. They would be able to overcome increases in flow resistance caused by biofouling and scar tissue growth. This study presents a proof of concept of a 1-mm-thick electromagnetic PDMS nozzle/diffuser micropump for biomedical applications. The pump is composed of a cast PDMS body, a spin coated PDMS membrane, and commercial silicone tubing, all bonded together with PDMS. Micromachining a pump cast enables multiple pumps to be produced quickly and reliably. An in-plane design is used to attach the inlet and outlet tubes. The pump produces a peak flow rate of 135 μL/min and a maximum backpressure of 25 mmH2O at an actuation frequency of 12 Hz and a duty cycle of 25%. The membrane thickness, actuator type, and duty cycle were shown to have a significant impact on the performance of the pump.

Paul Kawun

Papers

A thin PDMS nozzle/diffuser micropump for biomedical applications