Patents by Inventor David A. Walker

David A. Walker has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).

  • Patent number: 12350880
    Abstract: Methods and apparatus comprising a dewetting phase and a polymerization liquid that are immiscible, and can be used for the formation of three-dimensional objects, wherein the method does not require a dead zone. Additionally, methods and apparatus that employ an optically transparent cooling apparatus to mitigate heat generated during the fabrication process, and the use of a mobile phase to provide a shearing interface to reduce interfacial adhesive forces.
    Type: Grant
    Filed: September 6, 2022
    Date of Patent: July 8, 2025
    Assignee: NORTHWESTERN UNIVERSITY
    Inventors: Chad A. Mirkin, David A. Walker, James L. Hedrick, III
  • Patent number: 12214546
    Abstract: Methods and apparatus comprising a dewetting material and a polymerization liquid that are immiscible and dewetting, and can be used for the formation of three-dimensional objects, wherein the method does not require a dead zone. Additionally, methods and apparatus that employ the use of a flowing dewetting material to provide a shearing interface to reduce interfacial adhesive forces.
    Type: Grant
    Filed: March 9, 2020
    Date of Patent: February 4, 2025
    Assignee: NORTHWESTERN UNIVERSITY
    Inventors: David A. Walker, James L. Hedrick, III, Chad A. Mirkin
  • Publication number: 20240368392
    Abstract: A method of making a polyimide (PI)-based material. In one embodiment, the method begins by dispersing a polyamic acid (PAA) oligomer and photo-initiator into a photo-reactive monomer to form a liquid resin. In contrast to the above-described prior art, the liquid resin is substantially devoid of any non-reactive solvents. Electromagnetic radiation is then applied (e.g., in a 3D printing operation) to solidify the liquid resin and to substantially form a interpenetrating polymer network (IPN) in which the PAA oligomer is entangled within the network formed by the photo-reactive monomer but remains substantially independent and un-crosslinked from the PAA oligomer. Thereafter, the PAA-based IPN is thermally cycled to form a polyimide-based IPN.
    Type: Application
    Filed: May 2, 2024
    Publication date: November 7, 2024
    Inventors: David A. Walker, Matthew N. Pearlson
  • Publication number: 20230040818
    Abstract: Methods and apparatus comprising a dewetting phase and a polymerization liquid that are immiscible, and can be used for the formation of three-dimensional objects, wherein the method does not require a dead zone. Additionally, methods and apparatus that employ an optically transparent cooling apparatus to mitigate heat generated during the fabrication process, and the use of a mobile phase to provide a shearing interface to reduce interfacial adhesive forces.
    Type: Application
    Filed: September 6, 2022
    Publication date: February 9, 2023
    Inventors: Chad A. Mirkin, David A. Walker, James L. Hedrick, III
  • Patent number: 11465339
    Abstract: Methods and apparatus comprising a dewetting phase and a polymerization liquid that are immiscible, and can be used for the formation of three-dimensional objects, wherein the method does not require a dead zone. Additionally, methods and apparatus that employ an optically transparent cooling apparatus to mitigate heat generated during the fabrication process, and the use of a mobile phase to provide a shearing interface to reduce interfacial adhesive forces.
    Type: Grant
    Filed: May 31, 2017
    Date of Patent: October 11, 2022
    Assignee: NORTHWESTERN UNIVERSITY
    Inventors: Chad A. Mirkin, David A. Walker, James L. Hedrick, III
  • Patent number: 11415877
    Abstract: Disclosed herein are methods of using a fluoro oil mask to prepare a beam pen lithography pen array.
    Type: Grant
    Filed: December 7, 2017
    Date of Patent: August 16, 2022
    Assignee: NORTHWESTERN UNIVERSITY
    Inventors: Chad A. Mirkin, David A. Walker, James L. Hedrick, III
  • Publication number: 20220193988
    Abstract: Methods and apparatus comprising a dewetting material and a polymerization liquid that are immiscible and dewetting, and can be used for the formation of three-dimensional objects, wherein the method does not require a dead zone. Additionally, methods and apparatus that employ the use of a flowing dewetting material to provide a shearing interface to reduce interfacial adhesive forces.
    Type: Application
    Filed: March 9, 2020
    Publication date: June 23, 2022
    Inventors: David A. Walker, James L. Hedrick, III, Chad A. Mirkin
  • Patent number: 11292187
    Abstract: Methods and apparatus comprising a dewetting phase and a polymerization liquid that are immiscible, and can be used for the formation of three-dimensional objects, wherein the method does not require a dead zone. Additionally, methods and apparatus that employ an optically transparent cooling apparatus to mitigate heat generated during the fabrication process, and the use of a mobile phase to provide a shearing interface to reduce interfacial adhesive forces.
    Type: Grant
    Filed: October 30, 2020
    Date of Patent: April 5, 2022
    Assignee: NORTHWESTERN UNIVERSITY
    Inventors: Chad A. Mirkin, David A. Walker, James L. Hedrick, III
  • Publication number: 20210114288
    Abstract: Methods and apparatus comprising a dewetting phase and a polymerization liquid that are immiscible, and can be used for the formation of three-dimensional objects, wherein the method does not require a dead zone. Additionally, methods and apparatus that employ an optically transparent cooling apparatus to mitigate heat generated during the fabrication process, and the use of a mobile phase to provide a shearing interface to reduce interfacial adhesive forces.
    Type: Application
    Filed: October 30, 2020
    Publication date: April 22, 2021
    Inventors: Chad A. Mirkin, David A. Walker, James L. Hedrick, III
  • Publication number: 20190384161
    Abstract: Disclosed herein are methods of using a fluoro oil mask to prepare a beam pen lithography pen array.
    Type: Application
    Filed: December 7, 2017
    Publication date: December 19, 2019
    Inventors: Chad A. Mirkin, David A. Walker, James L. Hedrick, III
  • Publication number: 20190160733
    Abstract: Methods and apparatus comprising a dewetting phase and a polymerization liquid that are immiscible, and can be used for the formation of three-dimensional objects, wherein the method does not require a dead zone. Additionally, methods and apparatus that employ an optically transparent cooling apparatus to mitigate heat generated during the fabrication process, and the use of a mobile phase to provide a shearing interface to reduce interfacial adhesive forces.
    Type: Application
    Filed: May 31, 2017
    Publication date: May 30, 2019
    Inventors: Chad A. Mirkin, David A. Walker, James L. Hedrick, III
  • Patent number: 8473351
    Abstract: Authorization verification systems and methods are described that store a record of an authorization determination performed at a point of sale or other point of control. The system receives authorization information for an individual indicative of the individual's authorization to purchase a product or service, to enter a location, to attend an event, or to otherwise participate in an encounter whose access is limited to authorized individuals. In one embodiment, the authorization verification system receives information relating to the individual's age via an electronic scanning of a driver's license or other identification card, or by other methods, and uses the birth date information to calculate the customer's current age. The current age can be displayed on an existing display of a point-of-sale device or other display.
    Type: Grant
    Filed: March 11, 2003
    Date of Patent: June 25, 2013
    Assignee: First Data Corporation
    Inventors: Cassandra Mollett, Alan Jay Bethscheider, Susan Diane Brauckman, David A. Walker, David Wayne Smith
  • Patent number: 7769638
    Abstract: Authorization verification systems and methods are described that determine whether an authorization check is to be performed in conjunction with an online purchase or other electronic commerce transaction, and, if the authorization check is to be performed, that check the authorization of an individual wishing to participate in the online transaction and that store a retrievable record of the authorization check. The system receives authorization information for the individual that is indicative of the individual's authorization to purchase a product or service online, or to otherwise participate in an electronic commerce encounter whose access is limited to authorized individuals.
    Type: Grant
    Filed: March 11, 2003
    Date of Patent: August 3, 2010
    Assignee: First Data Corporation
    Inventors: Cassandra Mollett, Alan Jay Bethscheider, Susan Diane Brauckman, David A. Walker, David Wayne Smith
  • Patent number: 7191941
    Abstract: Authorization verification systems and methods are described that determine whether an authorization check is to be performed at a point of sale or other point of control, and, if the authorization check is to be performed, that check the authorization and that store a retrievable record of the authorization check. The system receives authorization information for an individual that is indicative of the individual's authorization to purchase a product or service, to enter a location, to attend an event, or to otherwise participate in an encounter whose access is limited to authorized individuals. In one embodiment, authorization for making a purchase is limited to individuals above an age threshold, and the authorization verification system receives information relating to the individual's age via an electronic scanning of a driver's license or other identification card, or by other methods, and uses the birth date information to calculate the customer's current age.
    Type: Grant
    Filed: March 11, 2003
    Date of Patent: March 20, 2007
    Assignee: First Data Corporation
    Inventors: Cassandra Mollett, Alan Jay Bethscheider, Susan Diane Brauckman, David A. Walker, David Wayne Smith
  • Patent number: 7182255
    Abstract: Systems and methods are described that determine a threshold value for an authorization check, such as an age verification, that is performed at a point of sale or other point of access control where access to a product, service, location, event, or the like, is restricted to individuals who meet an authorization threshold. In embodiments associated with purchases that comprise a variety of items for purchase and a variety of associated age-related authorization thresholds, systems and methods are described for determining an age-related authorization threshold for the purchase as a whole that will authorize the purchase of the items. In embodiments in which a purchaser's authorization is checked with respect to a determined threshold value, a record of the authorization check can be stored and can subsequently be retrieved to verify that an authorization check for the encounter was carried out using the determined threshold value.
    Type: Grant
    Filed: August 24, 2005
    Date of Patent: February 27, 2007
    Assignee: First Data Corporation
    Inventors: Cassandra Mollett, Alan Jay Bethscheider, Susan Diane Brauckman, David A. Walker, David Wayne Smith
  • Patent number: 6935559
    Abstract: Systems and methods are described that determine a threshold value for an authorization check, such as an age verification, that is performed at a point of sale or other point of access control where access to a product, service, location, event, or the like, is restricted to individuals who meet an authorization threshold. In embodiments associated with purchases that comprise a variety of items for purchase and a variety of associated age-related authorization thresholds, systems and methods are described for determining an age-related authorization threshold for the purchase as a whole that will authorize the purchase of the items. In embodiments in which a purchaser's authorization is checked with respect to a determined threshold value, a record of the authorization check can be stored and can subsequently be retrieved to verify that an authorization check for the encounter was carried out using the determined threshold value.
    Type: Grant
    Filed: June 25, 2004
    Date of Patent: August 30, 2005
    Assignee: First Data Corporation
    Inventors: Cassandra Mollett, Alan Jay Bethscheider, Susan Diane Brauckman, David A. Walker, David Wayne Smith
  • Publication number: 20040238630
    Abstract: Systems and methods are described that determine a threshold value for an authorization check, such as an age verification, that is performed at a point of sale or other point of access control where access to a product, service, location, event, or the like, is restricted to individuals who meet an authorization threshold. In embodiments associated with purchases that comprise a variety of items for purchase and a variety of associated age-related authorization thresholds, systems and methods are described for determining an age-related authorization threshold for the purchase as a whole that will authorize the purchase of the items. In embodiments in which a purchaser's authorization is checked with respect to a determined threshold value, a record of the authorization check can be stored and can subsequently be retrieved to verify that an authorization check for the encounter was carried out using the determined threshold value.
    Type: Application
    Filed: June 25, 2004
    Publication date: December 2, 2004
    Inventors: Cassandra Mollett, Alan Jay Bethscheider, Susan Diane Brauckman, David A. Walker, David Wayne Smith
  • Patent number: 6755344
    Abstract: Systems and methods are described that determine a threshold value for an authorization check, such as an age verification, that is performed at a point of sale or other point of access control where access to a product, service, location, event, or the like, is restricted to individuals who meet an authorization threshold. In embodiments associated with purchases that comprise a variety of items for purchase and a variety of associated age-related authorization thresholds, systems and methods are described for determining an age-related authorization threshold for the purchase as a whole that will authorize the purchase of the items. In embodiments in which a purchaser's authorization is checked with respect to a determined threshold value, a record of the authorization check can be stored and can subsequently be retrieved to verify that an authorization check for the encounter was carried out using the determined threshold value.
    Type: Grant
    Filed: March 11, 2003
    Date of Patent: June 29, 2004
    Assignee: First Data Corporation
    Inventors: Cassandra Mollett, Alan Jay Bethscheider, Susan Diane Brauckman, David A. Walker, David Wayne Smith
  • Patent number: 6722352
    Abstract: An internal combustion engine having an integrally connected pressure swing adsorption (PSA) system to provide oxygen-enriched air or oxygen-deficient air, in situ, to the mixing chamber of a spark-ignition or compression-ignition engine.
    Type: Grant
    Filed: November 6, 2001
    Date of Patent: April 20, 2004
    Assignee: Praxair Technology, Inc.
    Inventors: James Smolarek, David A. Walker, Bernard T. Neu
  • Patent number: D779513
    Type: Grant
    Filed: July 7, 2014
    Date of Patent: February 21, 2017
    Assignee: Microsoft Corporation
    Inventors: Oscar E. Murillo, Kristoffer S. Schultz, Cheryl Nicole Platz, Addison K. Linville, Kelly Rose McArthur, David A. Walker, Tyrone Samson, Vikram Bapat, John Henson, Jason Ryan Farmer, Craig Fox, Stefanie Lyn Tomko, Lisa Stifelman, Shane Jeremy Landry