Development of a Noninvasive Single Cell Manipulator Utilizing a TemperatureResponsive Polymer
Masayuki Yamato, Assistant Professor, Institute of Advanced Biomedical Engineering and Science,
Tokyo Women's Medical University
1. Introduction
Along with the recent miniaturization of physical objects insuch fields as medicine, engineering, agriculture, and biology,
there is an increased demand to establish methods for working in
microscopic environments, such as operating and processing
methods. With the developments in biotechnology over the past
several years, there is an increasing need for cell microinjection
and micromanipulation technologies in particular. The objectiveof this study is to provide an entirely new concept of
micromanipulation aimed at greatly improving cell operability andachieving low invasiveness by developing a micromanipulation
technique that uses temperature responsive polymers.

Above 32: : hydrophobic Promotes cell attachment
Manipulator tip
PIPAAmTarget cell

Below 32: : hydrophilic Promotes cell detachment

2. Temperature control for cell attachment anddetachment

Manipulator tip

In this study, a temperature-responsive polymer,
polyisopropylacrylamide (PIPAAm) was grafted onto the end
surface of the manipulator. The properties of the polymer
changes in response to temperature. By controlling temperature
with a small Peltier device, the property of the PIPAAm wasswitched between hydrophilic and hydrophobic to control cellattachment and detachment (Fig. 1). The cell-trapping domain
was ordered in an array by controlling the thickness of thetemperature-responsive polymer layer on the order ofnanometers and ablating the layer with UV excimer laser (Fig. 2).

Target cell
PIPAAmFig. 1 Single cell manipulator employing atemperature-responsive polymer3. Conclusion
It has been pointed out that cells can be damaged throughsingle-cell traps and other manipulation using physicaltechniques, such as optical tweezers and electric fields. The
technique for manipulating single cells used in the present
study, using temperature changes to control the chemical
nature of the manipulator surface, was found to be less invasive
than existing methods. This technique is expected to havepractical applications once the switching speed is improved.

Fig. 2 Array of orderly arranged hepatocytes

Construction of Micro-Lens Array by Micro-Fabrication of Stimuli-Responsive Gel
Yoshihiro Ito, Project Leader, Regenerative Medical Bioreactor Laboratory,
Kanagawa Academy of Science and Technology
A gel that expands and contracts in response to physicalstimuli, such as thermal, electrical, and optical variations, andchemical stimuli, such as pH and chemical substances, has begun
to attract much attention for its use as a soft functional material.
Now we have discovered a method enabling micromachining of
this type of stimuli-responsive gel. The objective of this study is toproduce a compound-eye lens as an application of the gel. Whilethe use of this gel for optical lenses has been considered before,
the greatest weakness of this substance is its lengthy stimulationresponse time. For example, a gel having a size of centimeters
requires several hours to respond to stimulation. However, thisresponse time can be shortened when reducing the size tomicrometers. In this study, we designed a compound-eye gel
micro-lens array with this gel, as shown in Fig. 1. We attempted toform the gel in a convex shape between micro-patterned ITO(indium tin oxide) transparent electrodes, controlling thethickness and focal length of the lenses individually by voltage.
Micro-lenses having a diameter of about 500 micrometers werearranged at regular intervals. Variations in response to pH andelectrical stimuli were observed within 1 second. Fig. 2 shows animage acquired using this micro-lens array. A toy dinosaur wasused as the subject of imaging. Variations in focal length inresponse to stimuli were observed from pH 7 to pH 2.

ITOelectrodes
GlassGelFig. 1 Principles of the compound-eye systemhaving an array of gel micro-lenses

Focal length

pH7

pH2

1100µm560µm

Fig. 2 An image taken by the compound-eye micro-lenses showing
variations in focal length in response to pH stimuli

2