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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Houston researchers make headway on affordable, sustainable sodium-ion battery

Energy Solutions

A new study by researchers from Rice University’s Department of Materials Science and NanoEngineering, Baylor University and the Indian Institute of Science Education and Research Thiruvananthapuram has introduced a solution that could help develop more affordable and sustainable sodium-ion batteries.

The findings were recently published in the journal Advanced Functional Materials.

The team worked with tiny cone- and disc-shaped carbon materials from oil and gas industry byproducts with a pure graphitic structure. The forms allow for more efficient energy storage with larger sodium and potassium ions, which is a challenge for anodes in battery research. Sodium and potassium are more widely available and cheaper than lithium.

“For years, we’ve known that sodium and potassium are attractive alternatives to lithium,” Pulickel Ajayan, the Benjamin M. and Mary Greenwood Anderson Professor of Engineering at Rice, said in a news release. “But the challenge has always been finding carbon-based anode materials that can store these larger ions efficiently.”

Lithium-ion batteries traditionally rely on graphite as an anode material. However, traditional graphite structures cannot efficiently store sodium or potassium energy, since the atoms are too big and interactions become too complex to slide in and out of graphite’s layers. The cone and disc structures “offer curvature and spacing that welcome sodium and potassium ions without the need for chemical doping (the process of intentionally adding small amounts of specific atoms or molecules to change its properties) or other artificial modifications,” according to the study.

“This is one of the first clear demonstrations of sodium-ion intercalation in pure graphitic materials with such stability,” Atin Pramanik, first author of the study and a postdoctoral associate in Ajayan’s lab, said in the release. “It challenges the belief that pure graphite can’t work with sodium.”

In lab tests, the carbon cones and discs stored about 230 milliamp-hours of charge per gram (mAh/g) by using sodium ions. They still held 151 mAh/g even after 2,000 fast charging cycles. They also worked with potassium-ion batteries.

“We believe this discovery opens up a new design space for battery anodes,” Ajayan added in the release. “Instead of changing the chemistry, we’re changing the shape, and that’s proving to be just as interesting.”

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This story originally appeared on EnergyCapitalHTX.com.

FAA demands investigation into SpaceX's out-of-control Starship flight

Out of this world

The Federal Aviation Administration is demanding an accident investigation into the out-of-control Starship flight by SpaceX on May 27.

Tuesday's test flight from Texas lasted longer than the previous two failed demos of the world's biggest and most powerful rocket, which ended in flames over the Atlantic. The latest spacecraft made it halfway around the world to the Indian Ocean, but not before going into a spin and breaking apart.

The FAA said Friday that no injuries or public damage were reported.

The first-stage booster — recycled from an earlier flight — also burst apart while descending over the Gulf of Mexico. But that was the result of deliberately extreme testing approved by the FAA in advance.

All wreckage from both sections of the 403-foot (123-meter) rocket came down within the designated hazard zones, according to the FAA.

The FAA will oversee SpaceX's investigation, which is required before another Starship can launch.

CEO Elon Musk said he wants to pick up the pace of Starship test flights, with the ultimate goal of launching them to Mars. NASA needs Starship as the means of landing astronauts on the moon in the next few years.

TMC med-tech company closes $2.5M series A, plans expansion

fresh funding

Insight Surgery, a United Kingdom-based startup that specializes in surgical technology, has raised $2.5 million in a series A round led by New York City-based life sciences investor Nodenza Venture Partners. The company launched its U.S. business in 2023 with the opening of a cleanroom manufacturing facility at Houston’s Texas Medical Center.

The startup says the investment comes on the heels of the U.S. Food and Drug Administration (FDA) granting clearance to the company’s surgical guides for orthopedic surgery. Insight says the fresh capital will support its U.S. expansion, including one new manufacturing facility at an East Coast hospital and another at a West Coast hospital.

Insight says the investment “will provide surgeons with rapid access to sophisticated tools that improve patient outcomes, reduce risk, and expedite recovery.”

Insight’s proprietary digital platform, EmbedMed, digitizes the surgical planning process and allows the rapid design and manufacturing of patient-specific guides for orthopedic surgery.

“Our mission is to make advanced surgical planning tools accessible and scalable across the U.S. healthcare system,” Insight CEO Henry Pinchbeck said in a news release. “This investment allows us to accelerate our plan to enable every orthopedic surgeon in the U.S. to have easy access to personalized surgical devices within surgically meaningful timelines.”

Ross Morton, managing Partner at Nodenza, says Insight’s “disruptive” technology may enable the company to become “the leader in the personalized surgery market.”

The startup recently entered a strategic partnership with Ricoh USA, a provider of information management and digital services for businesses. It also has forged partnerships with the Hospital for Special Surgery in New York City, University of Chicago Medicine, University of Florida Health and UAB Medicine in Birmingham, Alabama.

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