Houston founder shares how he's using tech to make digital media more effective and equitable

houston innovators podcast episode 173

This month, Mark Walker is celebrating his company's one year anniversary of going public — only the ninth Black-founded business to accomplish this feat on a U.S. stock exchange. Photo courtesy

After working in both sides of the advertising world, Mark Walker thought he could reimagine a platform that would be more efficient and equitable.

Walker co-founded his company, Direct Digital Holdings, an adtech platform, after serving in several roles — from an early hire at Houston digital media startup Questia to business development director at NRG Energy and COO of EBONY Media. He shares on the Houston Innovators Platform how he took this experience in tech, advertising, and media to create his company's platform.

"NRG Energy gave me a top-down view of the value chain, and Ebony gave me a bottoms-up view of the value chain of how media is purchased," Walker says on the show. "At Direct Digital Holdings, we help companies buy and sell media — and we leverage technology to do it. It's really the culmination of both of those experiences."

With over 30,000 publishers on its platform, Direct Digital makes it easier for its core customers — middle market companies looking to buy into the digital media ecosystem — to tap into these opportunities without the tech know-how they might otherwise need. Walker explains that at EBONY, he saw how small to midsize publications — especially the multicultural ones — were being left out on the ad selling side of the equation. The Direct Digital platform bridges the gap on each end.

Founded in 2018 in partnership with Keith Smith, who went through similar professional experiences, Direct Digital went public exactly one year ago after growing the company through strategic M&A activity. Walker says the decision to IPO made the most sense for his company — though it wasn't an easy process. Direct Digital is only the ninth company founded by a Black entrepreneur to go public on a US stock exchange.

"If you think the process is hard — it actually is," Walker says on the journey to IPO. "We were a privately held company, and we knew we had a good growth trajectory and we looked a couple different options. We decided to go public in a very traditional way."

Walker explains there were some risks involved, but the co-founders ultimately decided to shy away from adding in investors who might not have the same ideas for the company's future.

Direct Digital has been a Houston company from the star — despite the city not being home to a booming adtech ecosystem. Instead, Houston — with its collection of Fortune 500 companies and rich diversity — has allowed the business to stand out.

"If you look at and reflect on how our company has been built — from our board of directors to our leadership and management team — we're a majority minority organization all the way across the board," Walker says. "Diversity is very important to us. It's the lifeblood of our business — especially because we're serving publishers in those communities in big way. And moreso, we think you get the best product, thoughts, and ideas from a diverse workforce, and Houston fits right into that mold for us."

Walker shares more about his company's future, advice on IPO, and what all he's watching in adtech — from AI to streaming — on the podcast. Listen to the interview below — or wherever you stream your podcasts — and subscribe for weekly episodes.


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5 Houston universities named best in the world on new U.S. News list

Top of the Class

Five Houston-area universities have been named among the best universities worldwide in U.S. News & World Report's just-released comprehensive list for 2026-2027.

U.S. News' Best Global Universities report ranks more than 2,250 schools based exclusively on their academic research performance and international reputation. Only 275 universities from the U.S. were included in the global ranking, and 21 based in Texas.

Harvard University topped the list for 2026-2027, and the Massachusetts Institute of Technology and Stanford University claimed the coveted No. 2 and No. 3 spots worldwide.

Houston's Baylor College of Medicine topped the list of the best local schools, and it ranked as the 144th best university in the world.

Here's how the rest of Houston's local institutions ranked:

  • No. 201 – Rice University
  • No. 324 – University of Texas Health Science Center Houston
  • No. 390 – University of Houston
  • No. 599 – University of Texas Medical Branch Galveston

In a statement explaining global university trends, the managing editor for Education at U.S. News, LaMont Jones, Ed.D., said schools in the U.S. have continued to rank "disproportionately high" while major universities from other countries in China and South America are starting to catch up.

"The continuing strength of [American university] reputations and academic research are, for the most part, unmatched," he said. "It's why students all over the world flock here to learn."

Top-ranking Texas universities
The University of Texas at Austin ranked No. 1 statewide and No. 56 worldwide, further cementing the university's reputation as the top choice for students seeking a higher education in Texas.

Earlier in June, UT Austin ranked No. 35 in a separate list of the best universities in the world from the Center for World University Rankings, which compared 2,000 schools globally.

Here's where other Texas universities stand among the top 1,000 in this year's global rankings:

  • No. 113 – University of Texas Southwestern Medical Center, Dallas
  • No. 177 – Texas A&M University, College Station
  • No. 296 – University of Texas at San Antonio
  • No. 451 – Baylor University, Waco
  • No. 503 – University of Texas at Dallas
  • No. 562 – Texas Tech University, Lubbock
  • No. 739 – University of North Texas, Denton
  • No. 975 – University of Texas at Arlington
  • No. 944 – Southern Methodist University, Dallas
Additionally, six Texas universities ranked outside the top 1,000: University of Texas Rio Grande Valley (No. 1,153); University of Texas El Paso (No. 1,238); Texas State University in San Marcos (No. 1,531); Texas Tech University Health Sciences Center in Lubbock (No. 1,871); Texas Christian University in Fort Worth (No. 1,906); and Sam Houston State University in Huntsville (No. 2,141).

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This article originally appeared on CultureMap.com.

Rice student startup lands $1.85M to launch medical drone network

critical cargo

Students at Rice University have developed a medical cargo drone transport system to help deliver sensitive medical supplies and improve mobile healthcare efforts.

Haast Autonomous is the brainchild of graduating seniors Ege Halac, Jason Chen and Santiago Brent, who got their venture idea off the ground with help from the Liu Idea Lab for Innovation and Entrepreneurship (Lilie) Summer Venture Studio. The founders have developed the prototype at Rice’s Oshman Engineering Design Kitchen (OEDK) with fellow Rice researchers Felix Hasson, Ethan Javedan, Kenna Sanders and Caden Schmidt.

The startup has raised $1.85 million in pre-seed funding, according to Rice. The founders plan to focus on Haast full-time following graduation. They said they aim to launch pilot trials in 2027 and head to market later that year.

“We need better alternatives for a fast, safe and on-demand system of transport for life-critical cargo,” Halac said in a news release from Rice.

The Haast team has developed a custom aircraft with software that manages dispatch, routes, and chain of custody to assist in how materials move between sites in centralized medical systems. Generally, the transportation of medical supplies and materials between facilities and points of care relies on ground shipping or expensive air transport.

Haast Autonomous’ aircraft can take off and land vertically, and is designed around a mission profile of 50 to 62 miles. It can carry a payload of at least 5 pounds, with future versions intended to scale up in size. It also includes a built-in payload bay that regulates temperature, pressure, vibration and tilt to protect sensitive contents such as patient samples, antivenom or poisoning kits and radioligands or other therapies, according to Rice.

At first, the company envisioned the mission to be centered around transplants, but saw the product being best suited for a variety of operations.

“What we realized is that the platform we are building is suited for medicine, but it really underlies a much larger problem of mission-critical transport across industries,” Brent added in the news release. “We are building the fastest, most secure logistics chain for the world’s most sensitive cargo.”

Haast Autonomous was recognized at the 2026 Oshman Engineering Design Showcase and Competition, where it won Best Aerospace or Transportation Technology. It also performed well in the 2026 Napier Rice Launch Challenge.

In the future, Haast Autonomous plans to deploy a fleet of aircraft. The software will be designed to assist hospitals in requesting flights and tracking deliveries in real time.

“The drone is only part of the solution,” Chen also added in the release. “What matters is moving something from point A to point B in a way that fits into how hospitals already operate.”

Houston scientist wins prestigious Pew Scholar award for brain cancer research

standout scholar

Christina Tringides, an assistant professor of materials science and nanoengineering at Rice University, is one of 21 scientists to win a prestigious Pew Biomedical Scholar award.

She is the first faculty member from Rice to win the distinction, which provides $300,000 over four years for advances in biomedicine, according to the university. The awards are granted to researchers who are in the first few years at the assistant professor level.

In Tringides’ case, the funding will support her innovative new method of modeling glioblastoma, a common and extremely aggressive form of brain cancer. Thanks to producing its own blood supply, glioblastoma spreads quickly, weaving tendrils of blighted tissue throughout the brain. Because of this, surgery is difficult and conventional therapies ineffective.

Understanding the way glioblastoma spreads is crucial to the search for a cure. Tringides is using hydrogels that mimic the brain’s extracellular matrix. Using cultures and a microscopic labyrinth, her team can see how the cancer spreads, bonds with neurons and changes cell wall activity. Essentially, Tringides has devised an intelligence test for tumors in hopes of learning how to outsmart them.

“As cancer crawls through the maze, we can look at how it is interacting with the neurons more and more, and measure how electrical activity is changing as a result,” she said in a news release from Rice.

Examining how cancer cells grow can reveal which conditional changes slow them down. Finding ways to alter the structure of brain matter in a way that makes it inhospitable to the cancer could lead to therapies that would impede growth or even reverse it. Using her custom-made ersatz brain maze makes it easier to observe changes than it would be in a patient’s brain.

“Imaging synapses is time-intensive ⎯ it can involve large data files that are hard to visualize, but if we know that the only place where we might have a synapse is this tiny 1-by-4-by-10 micron channel, it makes it much faster and reliable to image them,” Tringides said.

Born in Ames, Iowa, Tringides received her doctorate in biophysics from Harvard before joining Rice in 2024 through a Cancer Prevention and Research Institute of Texas (CPRIT) recruitment award.

Her research was also one of the first four projects to receive research awards through the Rice Brain Institute and TMC Neuro Collaboration Seed Grant Program.

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