A Microfluidic Pump/Valve Inspired by Xylem Embolism and Transpiration in Plants

Li Jingmin,Zhang Kaiping,Liu Chong,Xu Zheng,Ke Xue,Wang Liding,Meni Wanunu

doi:10.1371/journal.pone.0050320

Abstract

In plants, transpiration draws the water upward from the roots to the leaves. However, this flow can be blocked by air bubbles in the xylem conduits, which is called xylem embolism. In this research, we present the design of a biomimetic microfluidic pump/valve based on water transpiration and xylem embolism. This micropump/valve is mainly composed of three parts: the first is a silicon sheet with an array of slit-like micropores to mimic the stomata in a plant leaf; the second is a piece of agarose gel to mimic the mesophyll cells in the sub-cavities of a stoma; the third is a micro-heater which is used to mimic the xylem embolism and its self-repairing. The solution in the microchannels of a microfluidic chip can be driven by the biomimetic “leaf” composed of the silicon sheet and the agarose gel. The halting and flowing of the solution is controlled by the micro-heater. Results have shown that a steady flow rate of 1.12 µl/min can be obtained by using this micropump/valve. The time interval between the turning on/off of the micro-heater and the halt (or flow) of the fluid is only 2∼3 s. This micropump/valve can be used as a “plug and play” fluid-driven unit. It has the potential to be used in many application fields.

Highlights

The micropump/valve is the ‘‘beating heart’’ of a microfluidic system [1,2]
Present micropumps/valves, have some disadvantages [5,6], such as requiring a continuous connection with external large equipments, expensive fabrication procedure and unsteady flow rate, which results in the difficulty in integrating these micropumps/valves onto a microfluidic device to obtain a true micro total analysis system
The chamber is filled with the agarose gel

Summary

Introduction

The micropump/valve is the ‘‘beating heart’’ of a microfluidic system [1,2]. The development of a miniaturized, portable, low cost and easy operation micropump/valve is important [3,4]. Transpiration is the loss of water through the slit-like stomata on the leaves, which may generate a water potential gradient in the stem vessels of a plant [7,8]. The water potential gradient lifts the water upward from the roots, via the xylem vessels and the mesophyll cells, eventually diffusing into the sub-cavities of the stomata (Fig. 1a). Xylem embolism (Fig. 1b) is mainly caused by cavitation [13]. It readily occurs at scorching heat and drought conditions in which the tension of water generated by the transpiration becomes great enough to separate the air from the water [14,15]. Solutes can be imported into the xylem conduits via the ray cells or via the bordered pits to redissolve the air-bubbles [16,17]

Methods

Results

Conclusion