WIRELESS MICROACTUATORS AND CONTROL METHODS

• US 20120310151A1
• Filed: 12/13/2011
• Published: 12/06/2012
• Est. Priority Date: 06/05/2011
• Status: Active Grant

• Current Assignee: University of British Columbia
• Original Assignee: University of British Columbia
• Inventors: Takahata, Kenichi, Ali, Mohamed Sultan Mohamed, Rahimi, Somayyeh
• Granted Patent: US 9,370,628 B2
• Time in Patent Office: Days
• US Class Current: 604/58
• CPC Class Codes: A61M 5/44 having means for cooling or heating the devices or media
• CPC Class Codes: B29C 2035/0811 using induction
• CPC Class Codes: B29C 2035/0827 using UV radiation
• CPC Class Codes: Y10T 156/10 Methods of surface bonding and/or assembly therefor

Abstract

Embodiments of the present technology include a micromachined implantable drug delivery devices, grippers, and syringes that are wirelessly powered and controlled by frequency tuning of external radiofrequency (RF) magnetic fields. An illustrative device can be designed and constructed with passive circuitry and microvalves that operate without batteries, e.g., through thermal actuation of hydrogel microvalves and/or shape-memory alloy members. The frequency selectivity in the device control provides not only a path to achieving reliable and safe operation of drug delivery but also potential applications for selective delivery of multiple drugs.

Claims

1. A microfluidic device comprising:

a reservoir to hold a substance, the reservoir including a release hole to dispense the substance;

a hydrogel microvalve disposed within the release hole, the hydrogel microvalve formed by;

filling the reservoir with a photosensitive hydrogel;

exposing the release hole to ultraviolet radiation to cure photosensitive hydrogel disposed within the release hole;

withdrawing uncured photosensitive hydrogel from the reservoir; and

a resonant heater in thermal communication with the hydrogel microvalve to actuate the hydrogel microvalve.

2. The microfluidic device of claim 1, wherein the substance is a fluid.

3. The microfluidic device of claim 1, wherein the substance is a powder.

4. The microfluidic device of claim 1, wherein the substance is a drug.

5. The microfluidic device of claim 1, wherein the hydrogel microvalve is self-aligned to the release hole.

6. The microfluidic device of claim 1, wherein the hydrogel microvalve comprises at least one of poly(N-isopropylacrylamide), poly(N,N-dimethylacrylamide-co-N-phenylacrylamide), and poly(glycidyl methacrylate-co-N-isopropylacrylamide).

7. The microfluidic device of claim 1, wherein the resonant heater is a planar resonant heater.

8. The microfluidic device of claim 1, wherein the resonant heater absorbs alternating current electromagnetic energy only at a predefined resonance.

9. The microfluidic device of claim 8, wherein the predefined resonance has a center frequency of about 10 MHz to about 1 GHz.

10. The microfluidic device of claim 8, wherein the predefined resonance has a active width of about 1 kHz to about 10 MHz.

11. The microfluidic device of claim 1, wherein the release hole is a first release hole, the hydrogel microvalve is a first hydrogel microvalve, the resonant heater is a first resonant heater configured to absorb electromagnetic energy at a first resonant frequency so as to actuate the first hydrogel microvalve, and further comprising:

a second release hole formed in the reservoir;

a second hydrogel microvalve disposed with the second release hole to prevent the substance from transiting the second release hole;

a second resonant heater configured to absorb electromagnetic energy at a second resonance frequency so as to actuate the second hydrogel microvalve.

12. A method of fabricating a hydrogel microvalve, the method comprising:

filling a reservoir having first and second release holes with a photosensitive hydrogel;

exposing the first release hole to ultraviolet radiation to cure photosensitive hydrogel disposed within the first release hole; and

withdrawing uncured photosensitive hydrogel from the reservoir via the second release hole to form the cured photosensitive hydrogel in the first release hole into a hydrogel microvalve.

13. The method of claim 12, wherein the photosensitive hydrogel comprises at least one of poly(N-isopropylacrylamide), poly(N,N-dimethylacrylamide-co-N-phenylacrylamide), and poly(glycidyl methacrylate-co-N-isopropylacrylamide).

14. The method of claim 12, wherein exposing the first release hole to ultraviolet radiation includes adjusting at least one of an exposure time and an exposure intensity to control dimensions of the hydrogel microvalve.

15. The method of claim 12, wherein an interior surface of the reservoir is formed or coated with polyimide, and further comprising:

treating the interior surface with an oxygen plasma before filling the reservoir with the photosensitive hydrogel to prevent adhesion of the photosensitive hydrogel to the interior surface.

16. The method of claim 12, further comprising:

forming or placing a resonant heater in thermal communication with the hydrogel microvalve.

17. The method of claim 16, wherein the resonant heater absorbs alternating current electromagnetic energy only at a predefined resonance.

18. An apparatus comprising:

a reservoir configured to hold a fluid;

a shape-memory alloy (SMA) member having a relaxed state and an actuated state; and

a resonant heater in thermal communication with the SMA member and configured to absorb electromagnetic energy at a resonance so as to actuate the SMA member from its relaxed state to its actuated state, thereby releasing at least some of the fluid from the reservoir.

19. The apparatus of claim 18, wherein the reservoir holds about 5 μ

L to about 50 μ

L of fluid.

20. The apparatus of claim 18, wherein the fluid comprises a drug.

21. The apparatus of claim 18, wherein, in its actuated state, at least part of the SMA member squeezes the reservoir.

22. The apparatus of claim 18, wherein actuating the SMA member from its relaxed state to its actuated state causes ejection of a predefined amount of fluid from the reservoir.

23. The apparatus of claim 21, wherein the predefined amount of fluid is about 1 μ

L to about 100 μ

L.

24. The apparatus of claim 18, wherein the SMA member is a first SMA member, the resonant heater is a first resonant heater, the resonance is a first resonance, and further comprising:

a second SMA member having a respective relaxed state and a respective actuated state; and

a second resonant heater in thermal communication with the second SMA member and configured to absorb electromagnetic energy at a second resonance so as to actuate the second SMA member from its respective relaxed state to its respective actuated state, thereby releasing additional fluid from the reservoir.

25. The apparatus of claim 24, wherein the first resonant heater absorbs electromagnetic energy only at the first resonance and wherein the second resonant heater absorbs electromagnetic energy only at the second resonance.

26. The apparatus of claim 25, wherein the first resonance has a center frequency that is about 1 MHz to about 100 MHz greater than that of the second resonance.

27. A method of fabricating a microsyringe, the method comprising:

depositing a resonant structure on a surface of a substrate;

forming a reservoir on or in the substrate;

bonding a shape-memory alloy (SMA) member to the surface of the substrate such that, when actuated, the SMA member ejects fluid from the reservoir; and

providing a thermal conduit from the resonant structure to the SMA.

29. The apparatus of claim 27, wherein the plurality of SMA members includes a first SMA member which, in its respective relaxed state, is in contact with a second SMA member in the plurality of SMA members, and which, in its respective actuated state, is separated from the second SMA member.

30. The apparatus of claim 27, wherein each resonant heater in the plurality of resonant heaters absorbs electromagnetic energy only at its respective resonance.

31. The apparatus of claim 30, wherein each resonant heater in the plurality of resonant heaters has a resonance at a center frequency that is about 1 MHz to about 100 MHz greater or smaller than the resonance of every other resonant heater in the plurality of resonant heaters.

28. An apparatus comprising:

a plurality of shape-memory alloy (SMA) members, each SMA member in the plurality of SMA members having a respective relaxed state and a respective actuated state;

a plurality of resonant heaters, each resonant heater in the plurality of resonant heaters in thermal communication with a corresponding SMA member in the plurality of SMA members and absorbing electromagnetic energy at a respective resonance so as to actuate the corresponding SMA member from its respective relaxed state to its respective actuated state.

32. A method of fabricating a wireless thermoresponsive microactuator, the method comprising:

depositing a resonant structure on a surface of a substrate;

bonding a shape-memory alloy (SMA) to the surface of the substrate; and

providing a thermal conduit from the resonant structure to the SMA.

33. The method of claim 32, wherein the substrate comprises a dielectric.

34. The method of claim 33, wherein the dielectric includes at least one of polyimide, glass, ceramic, and parylene.

35. The method of claim 32, wherein bonding the SMA to the surface includes electroplating the surface.

36. The method of claim 32, further comprising:

patterning the SMA into a member that actuates in response to absorption of alternating-current magnetic energy by the resonant structure.

37. The method of claim 36, wherein patterning the SMA includes micro-electro discharge machining the SMA member.