<?xml version="1.0" encoding="US-ASCII" standalone="no"?>
<!--Generated by ThunderDome XBRL - 06:50PM UTC 2026-05-13--><xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:country="http://xbrl.sec.gov/country/2026" xmlns:currency="http://xbrl.sec.gov/currency/2026" xmlns:dei="http://xbrl.sec.gov/dei/2026" xmlns:dtr-types="http://www.xbrl.org/dtr/type/2020-01-21" xmlns:ecd="http://xbrl.sec.gov/ecd/2026" xmlns:enum2="http://xbrl.org/2020/extensible-enumerations-2.0" xmlns:exch="http://xbrl.sec.gov/exch/2026" xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:lucd="http://www.luciddx.com/20260331" xmlns:naics="http://xbrl.sec.gov/naics/2026" xmlns:sic="http://xbrl.sec.gov/sic/2026" xmlns:srt="http://fasb.org/srt/2026" xmlns:srt-types="http://fasb.org/srt-types/2026" xmlns:stpr="http://xbrl.sec.gov/stpr/2026" xmlns:us-gaap="http://fasb.org/us-gaap/2026" xmlns:us-types="http://fasb.org/us-types/2026" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xmlns:xbrli="http://www.xbrl.org/2003/instance" xmlns:xlink="http://www.w3.org/1999/xlink" attributeFormDefault="unqualified" elementFormDefault="qualified" targetNamespace="http://www.luciddx.com/20260331">
  <xsd:import namespace="http://fasb.org/srt/2026" schemaLocation="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd"/>
  <xsd:import namespace="http://xbrl.sec.gov/ecd/2026" schemaLocation="https://xbrl.sec.gov/ecd/2026/ecd-2026.xsd"/>
  <xsd:import namespace="http://www.xbrl.org/2003/instance" schemaLocation="http://www.xbrl.org/2003/xbrl-instance-2003-12-31.xsd"/>
  <xsd:import namespace="http://xbrl.sec.gov/dei/2026" schemaLocation="https://xbrl.sec.gov/dei/2026/dei-2026.xsd"/>
  <xsd:import namespace="http://xbrl.sec.gov/exch/2026" schemaLocation="https://xbrl.sec.gov/exch/2026/exch-2026.xsd"/>
  <xsd:import namespace="http://xbrl.org/2005/xbrldt" schemaLocation="http://www.xbrl.org/2005/xbrldt-2005.xsd"/>
  <xsd:import namespace="http://xbrl.sec.gov/currency/2026" schemaLocation="https://xbrl.sec.gov/currency/2026/currency-2026.xsd"/>
  <xsd:import namespace="http://xbrl.sec.gov/country/2026" schemaLocation="https://xbrl.sec.gov/country/2026/country-2026.xsd"/>
  <xsd:import namespace="http://xbrl.sec.gov/naics/2026" schemaLocation="https://xbrl.sec.gov/naics/2026/naics-2026.xsd"/>
  <xsd:import namespace="http://www.xbrl.org/dtr/type/2020-01-21" schemaLocation="https://www.xbrl.org/dtr/type/2020-01-21/types.xsd"/>
  <xsd:import namespace="http://xbrl.org/2020/extensible-enumerations-2.0" schemaLocation="https://www.xbrl.org/2020/extensible-enumerations-2.0.xsd"/>
  <xsd:import namespace="http://xbrl.sec.gov/stpr/2026" schemaLocation="https://xbrl.sec.gov/stpr/2026/stpr-2026.xsd"/>
  <xsd:import namespace="http://xbrl.sec.gov/sic/2026" schemaLocation="https://xbrl.sec.gov/sic/2026/sic-2026.xsd"/>
  <xsd:import namespace="http://fasb.org/us-types/2026" schemaLocation="https://xbrl.fasb.org/us-gaap/2026/elts/us-types-2026.xsd"/>
  <xsd:import namespace="http://www.xbrl.org/2009/role/negated" schemaLocation="http://www.xbrl.org/lrr/role/negated-2009-12-16.xsd"/>
  <xsd:import namespace="http://fasb.org/srt-types/2026" schemaLocation="https://xbrl.fasb.org/srt/2026/elts/srt-types-2026.xsd"/>
  <xsd:import namespace="http://fasb.org/us-gaap/2026" schemaLocation="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd"/>
  <xsd:annotation>
    <xsd:appinfo>
      <link:linkbaseRef xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:href="lucd-20260331_lab.xml" xlink:role="http://www.xbrl.org/2003/role/labelLinkbaseRef" xlink:type="simple"/>
      <link:linkbaseRef xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:href="lucd-20260331_cal.xml" xlink:role="http://www.xbrl.org/2003/role/calculationLinkbaseRef" xlink:type="simple"/>
      <link:linkbaseRef xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:href="lucd-20260331_def.xml" xlink:role="http://www.xbrl.org/2003/role/definitionLinkbaseRef" xlink:type="simple"/>
      <link:linkbaseRef xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:href="lucd-20260331_pre.xml" xlink:role="http://www.xbrl.org/2003/role/presentationLinkbaseRef" xlink:type="simple"/>
      <link:roleType id="statement-document-and-entity-information" roleURI="http://www.luciddx.com/20260331/role/statement-document-and-entity-information">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">000 - Document - Document And Entity Information</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-condensed-consolidated-balance-sheets-current-period-unaudited" roleURI="http://www.luciddx.com/20260331/role/statement-condensed-consolidated-balance-sheets-current-period-unaudited">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">001 - Statement - Condensed Consolidated Balance Sheets (Current Period Unaudited)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-condensed-consolidated-balance-sheets-current-period-unaudited-parentheticals" roleURI="http://www.luciddx.com/20260331/role/statement-condensed-consolidated-balance-sheets-current-period-unaudited-parentheticals">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">002 - Statement - Condensed Consolidated Balance Sheets (Current Period Unaudited) (Parentheticals)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-condensed-consolidated-statements-of-operations-unaudited" roleURI="http://www.luciddx.com/20260331/role/statement-condensed-consolidated-statements-of-operations-unaudited">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">003 - Statement - Condensed Consolidated Statements of Operations (Unaudited)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-condensed-consolidated-statements-of-changes-in-stockholders-equity-deficit-unaudited" roleURI="http://www.luciddx.com/20260331/role/statement-condensed-consolidated-statements-of-changes-in-stockholders-equity-deficit-unaudited">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">004 - Statement - Condensed Consolidated Statements of Changes in Stockholders' Equity (Deficit) (Unaudited)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-condensed-consolidated-statements-of-changes-in-stockholders-equity-deficit-unaudited-parentheticals" roleURI="http://www.luciddx.com/20260331/role/statement-condensed-consolidated-statements-of-changes-in-stockholders-equity-deficit-unaudited-parentheticals">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">005 - Statement - Condensed Consolidated Statements of Changes in Stockholders' Equity (Deficit) (Unaudited) (Parentheticals)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-condensed-consolidated-statements-of-cash-flows-unaudited" roleURI="http://www.luciddx.com/20260331/role/statement-condensed-consolidated-statements-of-cash-flows-unaudited">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">006 - Statement - Condensed Consolidated Statements of Cash Flows (Unaudited)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-1-the-company" roleURI="http://www.luciddx.com/20260331/role/statement-note-1-the-company">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">007 - Disclosure - Note 1 - The Company</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-2-liquidity-and-going-concern" roleURI="http://www.luciddx.com/20260331/role/statement-note-2-liquidity-and-going-concern">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">008 - Disclosure - Note 2 - Liquidity and Going Concern</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-3-summary-of-significant-accounting-policies" roleURI="http://www.luciddx.com/20260331/role/statement-note-3-summary-of-significant-accounting-policies">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">009 - Disclosure - Note 3 - Summary of Significant Accounting Policies</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-4-revenue-from-contracts-with-customers" roleURI="http://www.luciddx.com/20260331/role/statement-note-4-revenue-from-contracts-with-customers">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">010 - Disclosure - Note 4 - Revenue from Contracts with Customers</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-5-related-party-transactions" roleURI="http://www.luciddx.com/20260331/role/statement-note-5-related-party-transactions">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">011 - Disclosure - Note 5 - Related Party Transactions</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-6-prepaid-expenses-deposits-and-other-current-assets" roleURI="http://www.luciddx.com/20260331/role/statement-note-6-prepaid-expenses-deposits-and-other-current-assets">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">012 - Disclosure - Note 6 - Prepaid Expenses, Deposits, and Other Current Assets</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-7-leases" roleURI="http://www.luciddx.com/20260331/role/statement-note-7-leases">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">013 - Disclosure - Note 7 - Leases</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-8-commitment-and-contingencies" roleURI="http://www.luciddx.com/20260331/role/statement-note-8-commitment-and-contingencies">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">014 - Disclosure - Note 8 - Commitment and Contingencies</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-9-financial-instruments-fair-value-measurements" roleURI="http://www.luciddx.com/20260331/role/statement-note-9-financial-instruments-fair-value-measurements">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">015 - Disclosure - Note 9 - Financial Instruments Fair Value Measurements</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-10-debt" roleURI="http://www.luciddx.com/20260331/role/statement-note-10-debt">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">016 - Disclosure - Note 10 - Debt</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-11-stockbased-compensation" roleURI="http://www.luciddx.com/20260331/role/statement-note-11-stockbased-compensation">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">017 - Disclosure - Note 11 - Stock-Based Compensation</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-12-stockholders-equity" roleURI="http://www.luciddx.com/20260331/role/statement-note-12-stockholders-equity">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">018 - Disclosure - Note 12 - Stockholders' Equity</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-13-net-loss-per-share" roleURI="http://www.luciddx.com/20260331/role/statement-note-13-net-loss-per-share">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">019 - Disclosure - Note 13 - Net Loss per Share</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-14-segment-information-" roleURI="http://www.luciddx.com/20260331/role/statement-note-14-segment-information-">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">020 - Disclosure - Note 14 - Segment Information</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-significant-accounting-policies-policies" roleURI="http://www.luciddx.com/20260331/role/statement-significant-accounting-policies-policies">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">995467 - Disclosure - Significant Accounting Policies (Policies)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-5-related-party-transactions-tables" roleURI="http://www.luciddx.com/20260331/role/statement-note-5-related-party-transactions-tables">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">995468 - Disclosure - Note 5 - Related Party Transactions (Tables)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-6-prepaid-expenses-deposits-and-other-current-assets-tables" roleURI="http://www.luciddx.com/20260331/role/statement-note-6-prepaid-expenses-deposits-and-other-current-assets-tables">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">995469 - Disclosure - Note 6 - Prepaid Expenses, Deposits, and Other Current Assets (Tables)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-7-leases-tables" roleURI="http://www.luciddx.com/20260331/role/statement-note-7-leases-tables">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">995470 - Disclosure - Note 7 - Leases (Tables)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-9-financial-instruments-fair-value-measurements-tables" roleURI="http://www.luciddx.com/20260331/role/statement-note-9-financial-instruments-fair-value-measurements-tables">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">995471 - Disclosure - Note 9 - Financial Instruments Fair Value Measurements (Tables)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-10-debt-tables" roleURI="http://www.luciddx.com/20260331/role/statement-note-10-debt-tables">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">995472 - Disclosure - Note 10 - Debt (Tables)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-11-stockbased-compensation-tables" roleURI="http://www.luciddx.com/20260331/role/statement-note-11-stockbased-compensation-tables">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">995473 - Disclosure - Note 11 - Stock-Based Compensation (Tables)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-13-net-loss-per-share-tables" roleURI="http://www.luciddx.com/20260331/role/statement-note-13-net-loss-per-share-tables">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">995474 - Disclosure - Note 13 - Net Loss per Share (Tables)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-2-liquidity-and-going-concern-details-textual" roleURI="http://www.luciddx.com/20260331/role/statement-note-2-liquidity-and-going-concern-details-textual">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">995475 - Disclosure - Note 2 - Liquidity and Going Concern (Details Textual)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-4-revenue-from-contracts-with-customers-details-textual" roleURI="http://www.luciddx.com/20260331/role/statement-note-4-revenue-from-contracts-with-customers-details-textual">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">995476 - Disclosure - Note 4 - Revenue from Contracts with Customers (Details Textual)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-5-related-party-transactions-aggregate-due-to-parent-details" roleURI="http://www.luciddx.com/20260331/role/statement-note-5-related-party-transactions-aggregate-due-to-parent-details">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">995477 - Disclosure - Note 5 - Related Party Transactions - Aggregate Due to Parent (Details)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-5-related-party-transactions-msa-fee-classification-details" roleURI="http://www.luciddx.com/20260331/role/statement-note-5-related-party-transactions-msa-fee-classification-details">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">995478 - Disclosure - Note 5 - Related Party Transactions - MSA Fee Classification (Details)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-6-prepaid-expenses-deposits-and-other-current-assets-prepaid-expenses-and-other-current-assets-details" roleURI="http://www.luciddx.com/20260331/role/statement-note-6-prepaid-expenses-deposits-and-other-current-assets-prepaid-expenses-and-other-current-assets-details">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">995479 - Disclosure - Note 6 - Prepaid Expenses, Deposits, and Other Current Assets - Prepaid Expenses and Other Current Assets (Details)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-7-leases-details-textual" roleURI="http://www.luciddx.com/20260331/role/statement-note-7-leases-details-textual">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">995480 - Disclosure - Note 7 - Leases (Details Textual)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-7-leases-lease-maturities-details" roleURI="http://www.luciddx.com/20260331/role/statement-note-7-leases-lease-maturities-details">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">995481 - Disclosure - Note 7 - Leases - Lease Maturities (Details)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-7-leases-cash-flow-information-on-leases-details" roleURI="http://www.luciddx.com/20260331/role/statement-note-7-leases-cash-flow-information-on-leases-details">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">995482 - Disclosure - Note 7 - Leases - Cash Flow Information on Leases (Details)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-9-financial-instruments-fair-value-measurements-details-textual" roleURI="http://www.luciddx.com/20260331/role/statement-note-9-financial-instruments-fair-value-measurements-details-textual">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">995483 - Disclosure - Note 9 - Financial Instruments Fair Value Measurements (Details Textual)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-9-financial-instruments-fair-value-measurements-fair-value-of-financial-instrument-details" roleURI="http://www.luciddx.com/20260331/role/statement-note-9-financial-instruments-fair-value-measurements-fair-value-of-financial-instrument-details">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">995484 - Disclosure - Note 9 - Financial Instruments Fair Value Measurements - Fair Value of Financial Instrument (Details)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-9-financial-instruments-fair-value-measurements-fair-value-assumptions-details" roleURI="http://www.luciddx.com/20260331/role/statement-note-9-financial-instruments-fair-value-measurements-fair-value-assumptions-details">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">995485 - Disclosure - Note 9 - Financial Instruments Fair Value Measurements - Fair Value Assumptions (Details)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-10-debt-details-textual" roleURI="http://www.luciddx.com/20260331/role/statement-note-10-debt-details-textual">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">995486 - Disclosure - Note 10 - Debt (Details Textual)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-10-debt-debt-instruments-details" roleURI="http://www.luciddx.com/20260331/role/statement-note-10-debt-debt-instruments-details">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">995487 - Disclosure - Note 10 - Debt - Debt Instruments (Details)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-10-debt-changes-in-fair-value-of-debt-details" roleURI="http://www.luciddx.com/20260331/role/statement-note-10-debt-changes-in-fair-value-of-debt-details">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">995488 - Disclosure - Note 10 - Debt - Changes in Fair Value of Debt (Details)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-11-stockbased-compensation-details-textual" roleURI="http://www.luciddx.com/20260331/role/statement-note-11-stockbased-compensation-details-textual">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">995489 - Disclosure - Note 11 - Stock-Based Compensation (Details Textual)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-11-stockbased-compensation-stock-option-activity-details" roleURI="http://www.luciddx.com/20260331/role/statement-note-11-stockbased-compensation-stock-option-activity-details">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">995490 - Disclosure - Note 11 - Stock-Based Compensation - Stock Option Activity (Details)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-11-stockbased-compensation-restricted-stock-activity-details" roleURI="http://www.luciddx.com/20260331/role/statement-note-11-stockbased-compensation-restricted-stock-activity-details">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">995491 - Disclosure - Note 11 - Stock-Based Compensation - Restricted Stock Activity (Details)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-11-stockbased-compensation-stockbased-compensation-expense-by-plan-details" roleURI="http://www.luciddx.com/20260331/role/statement-note-11-stockbased-compensation-stockbased-compensation-expense-by-plan-details">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">995492 - Disclosure - Note 11 - Stock-Based Compensation - Stock-Based Compensation Expense by Plan (Details)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-11-stockbased-compensation-unrecognized-compensation-expense-by-plan-details" roleURI="http://www.luciddx.com/20260331/role/statement-note-11-stockbased-compensation-unrecognized-compensation-expense-by-plan-details">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">995493 - Disclosure - Note 11 - Stock-Based Compensation - Unrecognized Compensation Expense by Plan (Details)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-11-stockbased-compensation-valuation-assumptions-details" roleURI="http://www.luciddx.com/20260331/role/statement-note-11-stockbased-compensation-valuation-assumptions-details">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">995494 - Disclosure - Note 11 - Stock-Based Compensation - Valuation Assumptions (Details)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-12-stockholders-equity-details-textual" roleURI="http://www.luciddx.com/20260331/role/statement-note-12-stockholders-equity-details-textual">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">995495 - Disclosure - Note 12 - Stockholders' Equity (Details Textual)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-13-net-loss-per-share-net-loss-per-share-details" roleURI="http://www.luciddx.com/20260331/role/statement-note-13-net-loss-per-share-net-loss-per-share-details">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">995496 - Disclosure - Note 13 - Net Loss per Share - Net Loss per Share (Details)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-13-net-loss-per-share-securities-excluded-from-computation-of-earnings-per-share-details" roleURI="http://www.luciddx.com/20260331/role/statement-note-13-net-loss-per-share-securities-excluded-from-computation-of-earnings-per-share-details">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">995497 - Disclosure - Note 13 - Net Loss per Share - Securities Excluded from Computation of Earnings per Share (Details)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-14-segment-information-details-textual" roleURI="http://www.luciddx.com/20260331/role/statement-note-14-segment-information-details-textual">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">995498 - Disclosure - Note 14 - Segment Information (Details Textual)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
    </xsd:appinfo>
  </xsd:annotation>
  <xsd:element abstract="true" id="lucd_AbeyanceSharesMember" name="AbeyanceSharesMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element id="lucd_AdjustmentsToAdditionalPaidInCapitalReleaseOfAbeyanceShares" name="AdjustmentsToAdditionalPaidInCapitalReleaseOfAbeyanceShares" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="duration"/>
  <xsd:element id="lucd_AdvancePaymentsToServiceProvidersAndSuppliers" name="AdvancePaymentsToServiceProvidersAndSuppliers" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="instant"/>
  <xsd:element id="lucd_AmortizationOfCommonStockPayments" name="AmortizationOfCommonStockPayments" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="lucd_AtthemarketOfferingMember" name="AtthemarketOfferingMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element id="lucd_ChangeInFairValueOfConvertibleDebt" name="ChangeInFairValueOfConvertibleDebt" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="duration"/>
  <xsd:element id="lucd_CommonStockSharesHeldInAbeyance" name="CommonStockSharesHeldInAbeyance" nillable="true" substitutionGroup="xbrli:item" type="xbrli:sharesItemType" xbrli:periodType="instant"/>
  <xsd:element id="lucd_CommonStockValueHeldInAbeyance" name="CommonStockValueHeldInAbeyance" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant"/>
  <xsd:element abstract="true" id="lucd_ConversionOfPreferredStockIntoCommonStockMember" name="ConversionOfPreferredStockIntoCommonStockMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="lucd_ConversionOfSeriesBPreferredStockIntoCommonStockMember" name="ConversionOfSeriesBPreferredStockIntoCommonStockMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="lucd_CostOfRevenueMember" name="CostOfRevenueMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element id="lucd_DebtInstrumentCovenantMaximumFairMarketStockPrice" name="DebtInstrumentCovenantMaximumFairMarketStockPrice" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:perShareItemType" xbrli:periodType="instant"/>
  <xsd:element id="lucd_DebtInstrumentCovenantMinimumAmountOfDebtIssuedAndOutstanding" name="DebtInstrumentCovenantMinimumAmountOfDebtIssuedAndOutstanding" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:percentItemType" xbrli:periodType="instant"/>
  <xsd:element id="lucd_DebtInstrumentCovenantMinimumCashAvailable" name="DebtInstrumentCovenantMinimumCashAvailable" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant"/>
  <xsd:element id="lucd_DebtInstrumentFairValueAdjustment" name="DebtInstrumentFairValueAdjustment" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="duration"/>
  <xsd:element id="lucd_DebtInstrumentFairValueAdjustmentNoninstallmentRepaymentsCashInterest" name="DebtInstrumentFairValueAdjustmentNoninstallmentRepaymentsCashInterest" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="duration"/>
  <xsd:element id="lucd_DebtInstrumentFairValueAdjustmentNoninstallmentRepaymentsInCommonStock" name="DebtInstrumentFairValueAdjustmentNoninstallmentRepaymentsInCommonStock" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="duration"/>
  <xsd:element id="lucd_DepositAssetsCurrent" name="DepositAssetsCurrent" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="instant"/>
  <xsd:element abstract="true" id="lucd_DocumentAndEntityInformation" name="DocumentAndEntityInformation" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element id="lucd_EmployeeRetentionCreditPayrollAndBenefits" name="EmployeeRetentionCreditPayrollAndBenefits" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="lucd_EmployeerelatedCostsMember" name="EmployeerelatedCostsMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element id="lucd_EquitySaleCommitmentMaximum" name="EquitySaleCommitmentMaximum" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant"/>
  <xsd:element id="lucd_FairValueOptionElectionPolicyTextBlock" name="FairValueOptionElectionPolicyTextBlock" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:textBlockItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="lucd_GeneralAndAdministrativeMember" name="GeneralAndAdministrativeMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="lucd_LucidDiagnostics2018EquityPlanMember" name="LucidDiagnostics2018EquityPlanMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="lucd_LucidEsppMember" name="LucidEsppMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="lucd_MeasurementInputRequiredRateOfReturnMember" name="MeasurementInputRequiredRateOfReturnMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="lucd_MsaFeesMember" name="MsaFeesMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="lucd_NoteToFinancialStatementDetailsTextual" name="NoteToFinancialStatementDetailsTextual" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="lucd_NotesToFinancialStatements" name="NotesToFinancialStatements" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="lucd_NotesToFinancialStatementsAbstract" name="NotesToFinancialStatementsAbstract" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element id="lucd_OboActivities" name="OboActivities" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="lucd_Pavmed2014EquityPlanMember" name="Pavmed2014EquityPlanMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="lucd_PavmedMember" name="PavmedMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="lucd_PavmedOboPaymentsMember" name="PavmedOboPaymentsMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element id="lucd_PaymentsToParent" name="PaymentsToParent" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="duration"/>
  <xsd:element id="lucd_PercentCommission" name="PercentCommission" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:percentItemType" xbrli:periodType="instant"/>
  <xsd:element id="lucd_PercentOfDividendsReceivable" name="PercentOfDividendsReceivable" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:percentItemType" xbrli:periodType="instant"/>
  <xsd:element abstract="true" id="lucd_PolicyTable" name="PolicyTable" nillable="true" substitutionGroup="xbrldt:hypercubeItem" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element id="lucd_PrepaidExpensesAndOtherCurrentAssetsTextBlock" name="PrepaidExpensesAndOtherCurrentAssetsTextBlock" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:textBlockItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="lucd_RegisteredDirectOfferingMember" name="RegisteredDirectOfferingMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="lucd_ResearchAndDevelopmentMember" name="ResearchAndDevelopmentMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="lucd_SaleOfCommonStockAsADividendMember" name="SaleOfCommonStockAsADividendMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="lucd_SalesAndMarketingMember" name="SalesAndMarketingMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element id="lucd_ScheduleOfChangesInTheFairValueOfDebtTableTextBlock" name="ScheduleOfChangesInTheFairValueOfDebtTableTextBlock" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:textBlockItemType" xbrli:periodType="duration"/>
  <xsd:element id="lucd_ScheduleOfUnrecognizedCompensationExpenseByPlanTableTextBlock" name="ScheduleOfUnrecognizedCompensationExpenseByPlanTableTextBlock" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:textBlockItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="lucd_SeriesAAndA1PreferredStockMember" name="SeriesAAndA1PreferredStockMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="lucd_SeriesB1PreferredStockHoldersMember" name="SeriesB1PreferredStockHoldersMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="lucd_SeriesB1PreferredStockMember" name="SeriesB1PreferredStockMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="lucd_SeriesB1PreferredStockOfferingMember" name="SeriesB1PreferredStockOfferingMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="lucd_SeriesBAndB1PreferredStockMember" name="SeriesBAndB1PreferredStockMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="lucd_SeriesBPreferredStockHoldersMember" name="SeriesBPreferredStockHoldersMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="lucd_SeriesBStockOfferingAndExchangeMember" name="SeriesBStockOfferingAndExchangeMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element id="lucd_SharebasedCompensationArrangementBySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodFairValue" name="SharebasedCompensationArrangementBySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodFairValue" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="duration"/>
  <xsd:element id="lucd_StockIssuedDuringPeriodSharesInterestPayment" name="StockIssuedDuringPeriodSharesInterestPayment" nillable="true" substitutionGroup="xbrli:item" type="xbrli:sharesItemType" xbrli:periodType="duration"/>
  <xsd:element id="lucd_StockIssuedDuringPeriodValueInterestPayment" name="StockIssuedDuringPeriodValueInterestPayment" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="duration"/>
  <xsd:element id="lucd_SummaryOfMsaFeeExpenseInIncomeStatementTableTextBlock" name="SummaryOfMsaFeeExpenseInIncomeStatementTableTextBlock" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:textBlockItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="lucd_The2024ConvertibleNotesMember" name="The2024ConvertibleNotesMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element id="lucd_WorkingCapital" name="WorkingCapital" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="lucd_statement-statement-note-10-debt-changes-in-fair-value-of-debt-details" name="statement-statement-note-10-debt-changes-in-fair-value-of-debt-details" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="lucd_statement-statement-note-10-debt-debt-instruments-details" name="statement-statement-note-10-debt-debt-instruments-details" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="lucd_statement-statement-note-10-debt-tables" name="statement-statement-note-10-debt-tables" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="lucd_statement-statement-note-11-stockbased-compensation-restricted-stock-activity-details" name="statement-statement-note-11-stockbased-compensation-restricted-stock-activity-details" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="lucd_statement-statement-note-11-stockbased-compensation-stock-option-activity-details" name="statement-statement-note-11-stockbased-compensation-stock-option-activity-details" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="lucd_statement-statement-note-11-stockbased-compensation-stockbased-compensation-expense-by-plan-details" name="statement-statement-note-11-stockbased-compensation-stockbased-compensation-expense-by-plan-details" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="lucd_statement-statement-note-11-stockbased-compensation-tables" name="statement-statement-note-11-stockbased-compensation-tables" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="lucd_statement-statement-note-11-stockbased-compensation-unrecognized-compensation-expense-by-plan-details" name="statement-statement-note-11-stockbased-compensation-unrecognized-compensation-expense-by-plan-details" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="lucd_statement-statement-note-11-stockbased-compensation-valuation-assumptions-details" name="statement-statement-note-11-stockbased-compensation-valuation-assumptions-details" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="lucd_statement-statement-note-13-net-loss-per-share-net-loss-per-share-details" name="statement-statement-note-13-net-loss-per-share-net-loss-per-share-details" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="lucd_statement-statement-note-13-net-loss-per-share-securities-excluded-from-computation-of-earnings-per-share-details" name="statement-statement-note-13-net-loss-per-share-securities-excluded-from-computation-of-earnings-per-share-details" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="lucd_statement-statement-note-13-net-loss-per-share-tables" name="statement-statement-note-13-net-loss-per-share-tables" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="lucd_statement-statement-note-5-related-party-transactions-aggregate-due-to-parent-details" name="statement-statement-note-5-related-party-transactions-aggregate-due-to-parent-details" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="lucd_statement-statement-note-5-related-party-transactions-msa-fee-classification-details" name="statement-statement-note-5-related-party-transactions-msa-fee-classification-details" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="lucd_statement-statement-note-5-related-party-transactions-tables" name="statement-statement-note-5-related-party-transactions-tables" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="lucd_statement-statement-note-6-prepaid-expenses-deposits-and-other-current-assets-prepaid-expenses-and-other-current-assets-details" name="statement-statement-note-6-prepaid-expenses-deposits-and-other-current-assets-prepaid-expenses-and-other-current-assets-details" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="lucd_statement-statement-note-6-prepaid-expenses-deposits-and-other-current-assets-tables" name="statement-statement-note-6-prepaid-expenses-deposits-and-other-current-assets-tables" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="lucd_statement-statement-note-7-leases-cash-flow-information-on-leases-details" name="statement-statement-note-7-leases-cash-flow-information-on-leases-details" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="lucd_statement-statement-note-7-leases-lease-maturities-details" name="statement-statement-note-7-leases-lease-maturities-details" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="lucd_statement-statement-note-7-leases-tables" name="statement-statement-note-7-leases-tables" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="lucd_statement-statement-note-9-financial-instruments-fair-value-measurements-fair-value-assumptions-details" name="statement-statement-note-9-financial-instruments-fair-value-measurements-fair-value-assumptions-details" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="lucd_statement-statement-note-9-financial-instruments-fair-value-measurements-fair-value-of-financial-instrument-details" name="statement-statement-note-9-financial-instruments-fair-value-measurements-fair-value-of-financial-instrument-details" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="lucd_statement-statement-note-9-financial-instruments-fair-value-measurements-tables" name="statement-statement-note-9-financial-instruments-fair-value-measurements-tables" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="lucd_statement-statement-significant-accounting-policies-policies" name="statement-statement-significant-accounting-policies-policies" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
</xsd:schema>
