The star stock-picker's fund bought about 165,000 American Depositary Receipts in the e-commerce group on Monday.
Wood's flagship Ark Innovation ETF fund purchased nearly 1.3 million shares of Robinhood during the company's first day of trading.
"Bitcoin mining will probably become part of utility ecosystems, and will proliferate renewables faster than would otherwise be the case," Wood said.
The ARK 21Shares Bitcoin ETF will track the S&P Bitcoin index and trade on the Cboe BZX Exchange under the ticker ARKB.
Cathie Wood's Ark funds loaded up on crypto-related investments Tuesday as bitcoin fell below $30,000. Wood sees bitcoin at $500,000 in the long term.
Wood's Ark Next Generation Internet ETF and Ark Space Exploration and Innovation ETF loaded up on Netflix shares as the streaming giant's stock tumbled Wednesday.
Cathie Wood's ARKX Space ETF now holds 5.8% of her own 3D printing ETF, more than the top 30 shareholders combined, according to Bloomberg data.
Wood's flagship fund bought the dip in Palantir on Wednesday as the data company saw its lowest closing price in almost four months.