Yuki Kihara

Fabrication and Application of 3-D Magnetically Driven Microtools

In this paper, we describe a novel method of fabricating polymeric 3-D magnetically driven microtools (MMTs) for performing nonintrusive and contamination-free experiments on chips. In order to obtain precise and complicated 3-D patterns from magnetically driven 3-D microtools, a grayscale photolithography technique was applied by making good use of a thick negative photoresist as a sacrifice mold. By controlling the amount of ultraviolet light with a gradation of gray-tone mask, we fabricated a smoothly curved (100-¿ m gap) object without steps, which tend to appear in the case of conventional layer-by-layer photolithography techniques. A wide range of on-chip applications of microactuators can be realized by using the softness of the polymer-based 3-D MMT. For example, a microfilter and a microloader were successfully operated by a combination of magnetic and fluidic forces. The finite element method analysis of flow showed that a rotation of the 3-D MMT produces a relatively strong downward axial flow, which prevents particles from stagnating on the surface of the MMT. The produced 3-D MMT can be applied to complex on-chip manipulations of sensitive materials such as cells.

On-chip magnetic 3D soft microactuators made by gray-scale lithography

In this paper we describe a novel fabrication method of three dimensional polymeric magnetically driven microtools (MMT) for non-intrusive and no contamination experiments on a chip. In order to obtain precise and complicated three dimensional patterns of magnetically driven 3D microtools, a grayscale photolithography technique has been applied by making good use of thick nega-photoresist as sacrificed mold. By controlling an amount of ultraviolet light with a gradation of gray tone mask, we have fabricated smoothly curved (100 mum gap) object without steps which tend to be appeared in case of conventional layer by layer photolithography techniques. A wide range of on-chip application of microactuators can be proposed by using a softness of polymer-based 3D MMT. For example, microrotor was operated as miromixer and micropump, also microloader was actuated by the magnetic and fluidic force. The surface of the 3D MMT was fabricated with a group of spiked pattern to reduce the contact area between PDMS (poly dimethyl siloxane) microchannel and PDMS-based 3D MMT. The produced 3D MMT can be applied to complicated on-chip manipulations of sensitive materials such as cells.

Formation of microdroplets utilizing hybrid magnetically driven microtool on a microfluidic chip

We proposed a polymer-metal hybrid MMT (magnetically driven microtool) which has properties of both elasticity and rigidity. A magnetic metal axle is made by electroplating, then it is mounted directly in the center of the MMT during molding. By using this process, we could fabricate a hybrid MMT whose fixed axes are elastic to move specific direction, while the center axle is rigid to prevent bending by the unwanted external force. The magnetic metal axle also has a merit to have higher magnetic property which contributes to the powerful actuation. We designed a hybrid MMT for on-demand droplet dispensing on a chip. It has a parallel plate structure to be constrained in translational motion. The displacement of the hybrid MMT was about 300 μm which was 6 times larger than that of the conventional MMT, and on-demand droplet generation was successfully performed. We confirmed production of the 177.7±2.3 μm droplet.

Active size controlled on-chip droplet dispensing by magnetically driven microtool

We have investigated an active size controlled droplet generation system by using magnetically driven microtool (MMT). With a lateral motion of the MMT in microchannels, the continuous phase can be pinched off by the movement of MMT to obtain size-controlled droplets actively. With this method, particle-enclosed droplet can be produced on demand to fit the size of each enclosed particle, and which is difficult to carry out only by the fluid dynamic force. For the current study, the system has been evaluated in terms of the frequency of the actuation of MMT and the size of the produced droplets, and found out the response time to change the droplet size by MMT actuation is one third of that only by the fluid dynamic force. This system contributes to the effective transportation of cells in microchannel.

2A2-L02 Magnetically Driven Robot-on-a-chip (MDRoC) : Part 2: Design and Fabrication of Hybrid MMT

We proposed a polymer-metal hybrid MMT (magnetically driven microtool) which has properties of both elasticity and rigidity. A magnetic metal axle is made by electroplating which is rigid to prevent bending by the unwanted external force. The magnetic metal axle also has a merit to have higher magnetic property which contributes to the powerful actuation. We designed a hybrid MMT for on-demand droplet dispensing on a chip. The displacement of the hybrid MMT was about 300 μm which was 6 times larger than that of the conventional MMT, and on-demand droplet generation was successfully performed. The MMT has potential to be used as micro-nano-robot on a chip which can be defined as Magnetically Driven Robot-on-a-Chip (MDRoC).

2P1-D13 On-chip cell manipulation systems : Part6: On-chip Droplet Dispensing by Magnetically Driven Microtool

References: Experiments: We have investigated an actively size controlled droplet generation system by using magnetically driven microtool (MMT). With this method cellenclosed droplet can be produced on demand to fit the size of each enclosed cell, and which is difficult to be carried out by fluid dynamic force. For the current study, the system has been evaluated in terms of the frequency of MMT actuation and the size of droplets produced and which contribute to the effective transportation of cells in microchannel