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Research Papers

Magnetic Shape Memory Micropump for Submicroliter Intracranial Drug Delivery in Rats

[+] Author and Article Information
Samuel Barker

Department of Mechanical and
Biomedical Engineering,
Department of Material Science
and Engineering,
Boise State University,
1910 University Drive,
Mail Stop 2090,
Boise, ID 83725-2090
e-mail: SamBarker@ASME.org

Eric Rhoads

Department of Mechanical and
Biomedical Engineering,
Department of Material Science
and Engineering,
Boise State University,
1910 University Drive,
Mail Stop 2090,
Boise, ID 83725-2090
e-mail: EricRhoads@u.boisestate.edu

Paul Lindquist

Department of Material Science
and Engineering,
Boise State University,
1910 University Drive,
Mail Stop 2090,
Boise, ID 83725-2090
e-mail: PaulLindquist@boisestate.edu

Martin Vreugdenhil

School of Clinical and Experimental Medicine,
University of Birmingham,
Vincent Drive,
Birmingham B15 2TT, UK
e-mail: m.vreugdenhil@bham.ac.uk

Peter Müllner

Department of Material Science
and Engineering,
Boise State University,
1910 University Drive,
Mail Stop 2090,
Boise, ID 83725-2090
e-mail: PeterMullner@boisestate.edu

Manuscript received March 30, 2016; final manuscript received August 18, 2016; published online September 12, 2016. Assoc. Editor: Xiaoming He.

J. Med. Devices 10(4), 041009 (Sep 12, 2016) (6 pages) Paper No: MED-16-1203; doi: 10.1115/1.4034576 History: Received March 30, 2016; Revised August 18, 2016

Point-of-care diagnostic devices, micrototal analysis (μTAS) systems, lab-on-a-chip development, and biomedical research rely heavily upon microfluidic management and innovative micropump design. Here, we describe the design and prototype deployment of a magnetic shape memory (MSM) micropump capable of submicroliter per minute flow rates. The pump contains no valves or moving parts in the fluid channel and is capable of bidirectional fluid transport. This pump was employed as the mechanism to deliver small intracranial dosages of ketamine and tetrodotoxin (TTX) at 0.33 μl/min during in vivo electrophysiological recordings in anesthetized rats, performing to required specifications.

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Figures

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Fig. 5

Flow rate data obtained prior to in vivo trials using water as fluid. Prior to in vivo trials, flow rate tests were performed at five rotational speeds. This figure represents data collected from a single representative micropump (CM162D2) over multiple trials with fixed motor controller input voltages.

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Fig. 4

The effect of local TTX application on the gamma power. (a) Lay-out of the experimental setup. The rat (1) was kept at 37 °C on a heating blanket (2) and fixed in a stereotaxic frame (3) by ear bars (4) and incisor bar (5). Electrodes were stereotaxically placed in burr holes (6) and local field potentials were by an MPA8 headstage (7) and AM3600 amplifier (8), digitized by a Power 4101 (9), controlled by spike 2 software (10). Guide cannulas (11) were placed such that the inserted quartz infusion cannula (12) perfused TTX locally. 1 μl TTX solution was supplied through a thin tube (13) driven by the MSM micropump (14) driven by an arduino (15) controlled by pulsed voltage output generated by spike software (16). (b) Local field potentials recorded from hippocampus area CA1 before (top trace), 15 min (middle trace) and 30 min (bottom trace) after the start of a 1 μl TTX application over 3 min. (c) Gamma power was determined as a running average from local field potential recordings in the hippocampus (CA1), visual cortex (VC), and prefrontal cortex (PFC). Gamma power was normalized to the average of the 5 min preceding the TTX application to CA1. Note that TTX reduces gamma power only in CA1.

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Fig. 3

(a) An annotated 3D render and (b) photograph of the MSM micropump prototype showing a coin to indicate scale. The arrow in (b) points toward the MSM element.

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Fig. 2

Schematic of the micropump pumping mechanism. The MSM element is attached to a glass plate and fixed in length. The magnetic field from a permanent magnet creates a localized shrinkage in the element. When the magnetic field is aligned with the fluid inlet (a), the shrinkage is created under the inlet and takes in fluid. As the magnet is rotated in the direction of the curved arrow, the shrinkage moves relative to the glass plate, transporting liquid from the fluid inlet to the fluid outlet along the MSM element (b). When the shrinkage passes the outlet (c), fluid is deposited and pressed into the outlet. An additional cycle is begun as the opposite pole of the magnetic field is aligned with the inlet (d).

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Fig. 1

Schematic graphical representation of four states of an MSM element constrained at each end with unit cells whose short axes are aligned parallel to the length of the element (vertical rectangles), and unit cells whose short axis are aligned perpendicular to the length of the element (horizontal rectangles) in response to an applied magnetic field. The broad arrow “H” indicates the position and direction of a localized magnetic field. The shrinkage (narrow section) appears at the position of the localized magnetic field. The narrow arrow “c-axis” indicates the orientation of the short (c-axis) direction.

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