The research explores the design, modelling, fabrication and testing of a thermoelectrically actuated microgripper for the manipulation of single cells and other biological particles. A suitable combination of conductive and polymeric materials together with the design of a highly efficient electro-thermal actuator has produced a microgripper that can be operated in air in in liquid environments without inducing electrolysis.It produces large deflections at low voltage and power. Micromanipulation experiments have succesfully demonstrated the gripping, holding and positioning of a micro sized object.
The aim of the project is to create a sensor which is capable of sensing ions associated with a single cell, in real time, while simultaneously manipulating that cell. The method of manipulation must not cause the cell any harm.
To do this, the project focuses on incorporating the working electrode of an electrochemical cell into the microgripper device, which was designed previously, and chemically modifying it to selectively detect specific ions.
This work has so far resulted in the successful fabrication of a thermally actuated U-shaped microgripper that has been specially designed to enable low voltage operation for bidirectional in plane deflection. The microgripper tips are carefully designed to match the biological species being manipulated, which has been demonstrated by the successful manipulation of 10 - 40 µm diameter particles used to simulate biological cells. We have also successfully modified the tips of the microgripper into an ion selective electrode (ISE) capable of sensing calcium ions at concentrations as low as 8x10-5 M. The modification involves adding poly(3,4-ethylenedioxythiophene) (PEDOT) to a gold electrode protruding from the microgripper tip, and then coating with a poly(vinyl chloride) PVC based calcium selective membrane. Excellent Nernstian response was observed from our devices, with calibration slopes of 29.5 ± 2.5 mV/dec.
A fabrication simulation video can be seen below:
The video below shows manipulation of cells using the microgrippers: